Tesis: "Soil Moisture Temperature Coupling"

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Attalla, Daniela, and Wu Jennifer Tannfelt. "Automated Greenhouse : Temperature and soil moisture control." Thesis, KTH, Maskinkonstruktion (Inst.), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-184599.

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In this thesis an automated greenhouse was built with the purpose of investigating the watering system’s reliability and if a desired range of temperatures can be maintained. The microcontroller used to create the automated greenhouse was an Arduino UNO. This project utilizes two different sensors, a soil moisture sensor and a temperature sensor. The sensors are controlling the two actuators which are a heating fan and a pump. The heating fan is used to change the temperature and the pump is used to water the plant. The watering system and the temperature control system was tested both separately and together. The result showed that the temperature could be maintained in the desired range. Results from the soil moisture sensor were uneven and therefore interpret as unreliable. I denna tes byggdes ett automatiserat växthus med syftet att undersöka dess bevattningssystems pålitlighet samt om ett önskat temperaturspann kan bibehållas. Microkontrollern för att bygga detta automatiserade växthus var en Arduino UNO. Detta projekt använder sig av två olika sensorer, en jordfuktsensor och en temperatursensor. Sensorerna kontrollerar en värmefläkt och en pump. Värmefläkten används för att ändra temperaturen och pumpen för att vattna plantan. Bevattningssystemet och temperaturstyrningen har testats både separat och tillsammans. Resultatet visar att temperaturen kan bibehållas inom det önskade spannet. Resultaten från jordfuktsensorn var ojämna och därför tolkats som opålitliga.

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El-Bishti, Magda Bashier. "Determination of soil moisture using dielectric soil moisture sensors : effect of soil temperature and implication for evaporation estimates." Thesis, University of Reading, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487102.

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The reliability and accuracy of several sensors that employ the relationship between dielectric constant and soil moisture constant, e, in particular capacitance sensors were investigated. Results obtained from laboratory examinations ,of a Theta probe, TP, selected as a representative model for capacitance sensors, suggested that the sensor output was affected by temperature variations, electrical conductivity levels, spatial variation in sample bulk density as well as the level of compaction of the soil surrounding the sensor's rods. Detailed in situ e data collected usmg capacitance sensors were used to calculate sub-daily estimates of evaporation, E, using the soil water balance method, combined with the zero-flux-plane (ZFP) approach, for plots of bare soil, rapeseed and a maize field. These sensors comprised Theta probes (TP), Profiles probes (PP), ECH20 probes (EP) and Aquaflex sensors (AF). / The field output data of these sensors were analysed and compared with e obtained with both, the gravimetric and neutron probe method. The absolute values of B as measured by the various capacitance sensors differed considerably. Furthermore, the outputs of these sensors (apart from the AF probes) were found to be affected by temperature, which would result in an anomalous course of diurnal E. Also, B-data were subject to noise which required smoothing to ensure a physically realistic variation in E, when compared to estimates with the Penman-Monteith equation, EPAf, and the eddy-covariance method (maize field). E was determined from diurnal changes in vertically integrated soil moisture content above the ZFP. Smoothed values of Bwere temperature-corrected using fieldbased and laboratory-based correction equations. A considerable difference between field- and laboratory-based temperature corrections procedures was noticed, and correction factors strongly depended on B. As this resulted in an overly complicated correction procedure, which consequently gave unreliable E-values, it was then decided to use a constant correction factor (based on the field correction procedure), for each capacitance probe. For the bare soil plot, with the exception ofPP and EP only Bprofiles obtained with the TP and AF sensors produced relatively reliable E values when compared to Enf. By contrast, when these capacitance sensors were used under a canopy, all sensors yielded satisfactory E-values. This was most likely caused by reduced amplitudes of soil temperatures under the canopy and the fact that the dimensions of most sensors do not allow installation in the top soil (~3-5cm) layer at which most evaporation would take place in bare soils. We therefore recommended that these sensors can be used for diurnal B measurements and E determination under canopy provided that an appropriate temperature-correction procedure for each sensor is applied. To obtain reliable Band E estimates in bare soil, more research needs to be done. For more reliable e and E estimations in bare soils further extensive field trials would be strongly advised

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Franks, Carol Dawn. "Temperature, moisture and albedo properties of Arizona soils." Thesis, The University of Arizona, 1985. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1985_263_sip1_w.pdf&type=application/pdf.

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Alvenäs, Gunnel. "Evaporation, soil moisture and soil temperature of bare and cropped soils /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5714-9.pdf.

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Low, Spencer Nishimoto. "An Exploration of Soil Moisture Reconstruction Techniques." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/9169.

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Satellite radiometers are used to remotely measure properties of the Earth's surface. Radiometers enable wide spatial coverage and daily temporal coverage. Radiometer measurements are used in a wide array of applications, including freeze/thaw states inference, vegetation index calculations, rainfall estimation, and soil moisture estimation. Resolution enhancement of these radiometer measurements enable finer details to be resolved and improve our understanding of Earth. The Soil Moisture Active Passive (SMAP) radiometer was launched in April 2014 with a goal to produce high resolution soil moisture estimates. However, due to hardware failure of the radar channels, prepared algorithms could no longer be used. Current algorithms utilize a narrow spatial and temporal overlap between the SMAP radiometer and the SENTINEL-1 radar to produce high resolution soil moisture estimates that are spatially and temporally limited. This thesis explores the use of resolution enhancing algorithms to produce high resolution soil moisture estimates without the spatial coverage limitations caused by using multiple sensors. Two main approaches are considered: calculating the iterative update in brightness temperature and calculating the update in soil moisture. The best performing algorithm is the Soil Moisture Image Reconstruction (SMIR) algorithm that is a variation of the Radiometer form of the Scatterometer Image Reconstruction (rSIR) algorithm that has been adapted to operate in parameter space. This algorithm utilizes a novel soil moisture measurement response function (SMRF) in the reconstruction. It matches or exceeds the performance of other algorithms and allows for wide spatial coverage.

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Post, Donald F., Jamie P. Dubay, and Allan D. Matthias. "The Effects of Rock and Green Waste Mulches on Soil Moisture and Soil Temperature." Arizona-Nevada Academy of Science, 2000. http://hdl.handle.net/10150/296563.

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Adu-Gyamfi, Kwame. "Laboratory calibration of soil moisture, resistivity, and temperature probe - Capacitance probe." Ohio : Ohio University, 2001. http://www.ohiolink.edu/etd/view.cgi?ohiou1173385776.

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Brewer, Robert Wayne. "Summer Regional United States Diurnal Temperature Range Variability With Soil Moisture Conditions." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1428939308.

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9

Dilawari, Geetika. "Analysis of the influence of soil temperature and soil surface conditions on soil moisture estimation using the Theta Probe." [Ames, Iowa : Iowa State University], 2006.

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10

Matheron, Michael, Martin Porchas, and Michael Maurer. "Effect of Temperature and Moisture on Survival of Phytophthora in Citrus Grove Soil." College of Agriculture, University of Arizona (Tucson, AZ), 2000. http://hdl.handle.net/10150/223839.

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Before replanting a citrus grove in Arizona, different preplant cultural activities may be performed, such as immediate replanting of the new citrus grove, allowing soil to lay fallow for various lengths of time, or planting the site to alfalfa for one or more years before the new citrus grove is established. A study was conducted to compare the effect of these different cultural preplant practices on the survival of Phytophthora in citrus grove soils. In June, 1998, and July, 1999, a total of 18 soil samples were collected within mature lemon groves. Each initial bulk sample was pretested, found to contain Phytophthora parasitica, then thoroughly mixed and partitioned into 1-liter plastic containers, which were subjected to different environmental and cultural conditions. The soil in each 1-liter container was tested for the presence of P. parasitica 1 and 3.5 to 4 months later. All soil samples then were placed in the greenhouse and a 6-month-old Citrus volkameriana seedling was planted in soil samples not containing plants. Three 1-liter sub-samples from each of ten 7-liter volumes of soil incubated outside for three months were also planted to citrus in the greenhouse. The soil containing plants in the greenhouse was watered as needed for 3 months, then again tested for the presence of Phytophthora. Irrigating soil infested with Phytophthora parasitica, whether it was planted to a host (citrus) of the pathogen, planted to a non-host (alfalfa) of the pathogen, or not planted at all, did not lower the pathogen to nondetectable levels. Phytophthora became and remained nondetectable only in the soil samples that were not irrigated and subjected to mean temperatures of 35 to 37° C (94 to 98° F). On the other hand, the pathogen was detectable in some soil samples subjected to dryness at lower mean temperatures of 26 to 30° C (79 to 86° F) after a citrus seedling subsequently was grown in the soil for 3 months. A dry summer fallow period following removal of a citrus grove (including as much root material as possible) was the only cultural practice among those tested that reduced the level of Phytophthora to nondetectable levels in all soil samples tested.

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Uchaipichat, Anuchit Civil &amp Environmental Engineering Faculty of Engineering UNSW. "Experimental investigation and constitutive modelling of thermo-hydro-mechanical coupling in unsaturated soils." Awarded by:University of New South Wales. School of Civil and Environmental Engineering, 2005. http://handle.unsw.edu.au/1959.4/22068.

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A thermo-elastic-plastic model for unsaturated soils has been presented based on the effective stress principle considering the thermo-mechanical and suction coupling effects. The thermo-elastic-plastic constitutive equations for stress-strain relations of the solid skeleton and changes in fluid content and entropy for unsaturated soils have been established. A plasticity model is derived from energy considerations. The model derived covers both associative and non-associative flow behaviours and the modified Cam-Clay is considered as a special case. All model coefficients are identified in terms of measurable parameters. To verify the proposed model, an experimental program has been developed. A series of controlled laboratory tests were carried out on a compacted silt sample using a triaxial equipment modified for testing unsaturated soils at elevated temperatures. Imageprocessing technique was used for measuring the volume change of the samples subjected to mechanical, thermal and hydric loading. It is shown that the effective critical state parameters M, ???? and ???? are independent of temperature and matric suction. Nevertheless, the shape of loading collapse (LC) curve was affected by temperature and suction. Furthermore, the temperature change affected the soil water characteristic curve and an increase in temperature caused a decrease in the air entry suction. The simulations from the proposed model are compared with the experimental results. The model calibration was performed to extract the model parameters from the experimental results. Good agreement between the results predicted using the proposed model and the experimental results was obtained in all cases.

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Acosta, Alvaro. "Estimating diurnal patterns of water uptake by roots from detailed measurement of soil moisture and soil temperature gradients." Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269928.

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13

Mohammad, Abdul KADER. "Effectiveness of various types of mulching on soil moisture and temperature regimes under rainfed soybean cultivation." Kyoto University, 2020. http://hdl.handle.net/2433/259050.

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Kyoto University (京都大学) 0048 新制・課程博士 博士(農学) 甲第22782号 農博第2425号 新制||農||1081(附属図書館) 学位論文||R2||N5302(農学部図書室) 京都大学大学院農学研究科地域環境科学専攻 (主査)教授中村公人, 教授星野敏, 教授藤原正幸 学位規則第4条第1項該当

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Fuhrer, Oliver. "Inverse heat conduction in soils : a new approach towards recovering soil moisture from temperature records /." Zürich : ETH IKF, 2000. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=114.

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15

Williams, Todd Joseph. "Effects of temperature and moisture content on transport of organic vapours in dual-porosity soil." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0025/MQ50379.pdf.

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16

Elson, Marshall Kent. "Influence of temperature, soil moisture, and planting depth on germination and emergence of 'Packman' broccoli." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/45969.

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Broccoli growers in southside Virginia have had difficulty with stand establishment. This research was undertaken to identify potential causes of poor stand establishment. Temperature and soil moisture conditions in southside Virginia during July and August are often less than favorable for seedling growth. Experiments were designed to test the temperature and moisture stress limits for germination and emergence of 'Packman' broccoli, under the controlled conditions of growth chambers. Master of Science

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Kingsley-Richards, Sarah. "Influence of Plant Age, Soil Moisture, and Temperature Cylcing Date on Containter-Grown Herbaceous Perennials." ScholarWorks @ UVM, 2011. http://scholarworks.uvm.edu/graddis/122.

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Perennial growers overwintering plant stock require information to assist in deciding which containerized plants are most likely to successfully overwinter. Three studies on container-grown herbaceous perennials were conducted to examine the influence of plant age, soil moisture, and temperature cycling date on cold hardiness. In January, plants were exposed to controlled freezing temperatures of -2, -5, -8, -11, and -14C and then returned to a 3-5C greenhouse. In June, plants were assessed using a visual rating scale of 1-5 (1 = dead, 3-5 = increasing salable quality, varying by cultivar) and dry weights of new growth were determined. Controlled freezing in November and March were also included in the third study. In the first study, two ages of plants were exposed to controlled freezing temperatures in January. For Geranium x cantabrigiense 'Karmina', age had no effect on either rating or dry weight in one study year. In two Sedum 'Matrona' study years, age had no effect on dry weight but ratings were higher for older plants than younger plants in the first year and higher for younger plants than older plants in the second year. In two Leucanthemum x superbum 'Becky' study years, age had an effect on both rating and dry weight which were both generally higher for younger plants than older plants. In the second study, plants were maintained in pots at two different soil moisture levels prior to exposure to controlled freezing temperatures in January. Coreopsis 'Tequila Sunrise' and Carex morrowii 'Ice Dance' showed no effect on either rating or dry weight from soil moisture level. Soil moisture level had no effect on dry weight but ratings were higher for Geranium x cantabrigiense 'Cambridge' “wet” plants and for Heuchera 'Plum Pudding' “dry” plants. Carex laxiculmus 'Hobb' (Bunny Blue™) soil moisture level had an effect where dry weight was higher for “dry” plants. Means at were of salable quality for Geranium and Heuchera at all temperatures and Carex laxiculmus at temperatures above -11C. The effects of soil moisture level on Carex oshimensis were inconclusive. In the third study, during November, January, and March, plants were subjected to temperature cycling treatments prior to exposure to controlled freezing temperatures. Geranium x cantabrigiense 'Cambridge' were more tolerant of both temperature cycling and freezing temperatures in January and an increased number of cycles in November had an advantageous effect. Sedum 'Matrona' were more tolerant of temperature cycling and freezing temperatures in January and an increased number of cycles in March had an advantageous effect. Leucanthemum x superbum 'Becky' were more tolerant of temperature cycling in January in the second year of the study and an increased number of cycles in November had an advantageous effect in the first year and in all months in the second year. Overwintering younger container-grown plants is likely to result in more growth and higher quality following exposure to freezing temperatures. Effects of soil moisture level on overwintering container-grown plant growth and quality are cultivar-specific and a general effect could not be established in these studies. Overwintering container-grown plants are likely to be hardier in January and slight temperature cycles prior to exposure to freezing temperatures generally increase hardiness.

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18

Zhou, Zhengming. "Non-linear elastic modelling of coupled deformation, heat, air and moisture transfer in unsaturated soil." Thesis, Cardiff University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360637.

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19

Teclehaimanot, Dawit Lee Jejung. "Quantitative analysis of moisture content and temperature of landfill soil cover and their effect on methane emission." Diss., UMK access, 2005.

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Thesis (M.S.)--Dept. of Geosciences. University of Missouri--Kansas City, 2005. "A thesis in urban environmental geology." Typescript. Advisor: Jejung Lee. Vita. Title from "catalog record" of the print edition Description based on contents viewed March 12, 2007. Includes bibliographical references (leaves 116-119). Online version of the print edition.

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20

Wolchansky, Jennifer E. "Effects of simulated grazing on soil temperature, moisture, and respiration on a shortgrass steppe in northeastern Colorado." Diss., Connect to online resource, 2005. http://wwwlib.umi.com/cr/colorado/fullcit?p1427769.

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Luo, Lei. "Proposing an improved surface dryness index to estimate soil moisture based on the temperature vegetation dryness index." Thesis, Kansas State University, 2016. http://hdl.handle.net/2097/34605.

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Master of Arts Department of Geography Douglas Goodin In this thesis, I proposed a new surface dryness index based on the slope of soil moisture isolines in the Land Surface Temperature/Normalized Difference Vegetation Index (LST/NDVI) feature space. This index, referred to here as Dryness Slope Index (DSI), overcomes the problem of Temperature Vegetation Dryness Index (TVDI) having different basis when calculating TVDI values across different images. This problem is rooted in the definition of TVDI whose calculation depends on the position of the “dry edge” and “wet edge” of pixels’ values in the LST/NDVI space of a specific image. The “wet edge” has a fairly stable physical meaning, which represents soil at field capacity or above, and it remains stable across a time series of images. However, the position of “dry edge” represents the driest condition in the image, which does not necessarily mean that the soil is completely dry. Therefore, the value of TVDI calculated from different images is not based on an invariant dry edge value as its baseline, and it is therefore likely to lead to incorrect conclusion if used without extra examination. This problem manifests itself when comparing TVDI values from different images with meteorological data. Results from similar analyses done with DSI showed more reasonable match with the validation data, indicating DSI is a more robust surface dryness index than TVDI. Having verified DSI can be effectively used in estimating soil moisture, I applied DSI on Landsat5 TM to study the relationship between soil moisture and land cover, slope, aspect, and relative elevation. Results showed that land cover accounts the most for variations of estimated soil moisture. I also applied DSI on a long time-series (2000 to 2014) of MODIS data trying to explore the temporal evolution of soil moisture in the entire Flint Hills ecoregion. Results showed little correlation between time and estimated soil moisture, indicating that no noticeable changes in soil moisture has been found through all these years.

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Franca, Lucas Xavier. "EMERGENCE PATTERNS OF COMMON WATERHEMP AND PALMER AMARANTH IN SOUTHERN ILLINOIS." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1756.

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The continued spread of glyphosate-resistant common waterhemp [Amaranthus tuberculatus (Moq.) Sauer (syn. rudis)] and Palmer amaranth [Amaranthus palmeri (S. Wats.)] have complicated weed control efforts in soybean and corn production in Illinois. A thorough understanding of the weed biology of these species is fundamental in developing effective weed management strategies. The determination of emergence patterns as well as the influence of tillage practices on soil microclimate and soil seed bank will allow control strategies to be implemented at the most effective timing. Field experiments were conducted in southern Illinois throughout the growing season of 2013 and 2014 on two separate sites with populations of common waterhemp and Palmer amaranth. Three tillage treatments were evaluated: no-tillage; early tillage, preferably performed around a recommended soybean planting date of May 1st; and late tillage, preferably performed on June 1st to simulate a late soybean planting. Amaranthus seedlings were identified and enumerated in the center 1 m2 quadrat of each plot within a 7-day interval from April through November or first frost. All weed seedlings were removed from the plot area after each enumeration. Soil temperature and soil moisture were recorded hourly throughout the experiment using data loggers established in the plot area. First emergence of common waterhemp occurred earlier in the season than did Palmer amaranth. In 2013, initial emergence of common waterhemp and Palmer amaranth was observed at the first and second week of May, respectively. In 2014, initial common waterhemp emergence was observed in late April, while Palmer amaranth initial emergence was similar to previous year. Palmer amaranth emerged over a longer period compared to waterhemp. By the end of June, 90% of common waterhemp had emerged regardless of tillage or year. By the same measure, Palmer amaranth emergence was extended to the third week of July and second week of August in 2013 and 2014, respectively. Soil temperature did not differ across tillage treatments in both years. On the other hand, differences in soil moisture were observed, mostly over two weeks following each tillage operation. The single best predictor for common waterhemp emergence was soil temperature (weekly highs and lows) followed by soil moisture. For Palmer amaranth emergence the single best predictor was spikes in soil moisture (high for the week). In 2013, common waterhemp emergence was initially positively and later in the growing season negatively interacted with maximum temperature 13 days prior to counts, with temperatures above 30 C observed with decreased emergence (R2 = 0.35). In the same year spikes in soil moisture interacted with Palmer amaranth emergence were those observed 11 days before each seedling enumeration date (R2 = 0.30). In 2014, with first common waterhemp emergence in April, a positive interaction to high soil temperature was initially observed followed by a positive interaction to minimum temperatures later in the season (R2 = 0.55). Spikes in soil moisture observed 2 weeks prior to emergence and weekly high temperatures 8 days prior to emergence were the best predictors of Palmer amaranth emergence in 2014 (R2 =0.37). Soil seed bank depletion was also estimated by comparing field emergence with greenhouse experiment results of soil seed bank estimation. Greater emergence of common waterhemp from the soil seed bank was observed in early tillage in 2013 and no-tillage in 2014 than late tillage, respectively; for Palmer amaranth, the greatest emergence from the soil seed bank was observed in no-tillage and late tillage in 2013, and no-tillage, in 2014. The emergence patterns observed in this research suggest that although common waterhemp and Palmer amaranth exhibit discontinuous emergence throughout the growing season, greater attention should be placed on managing peaks of emergence from late April to late July, which is critical to provide a foundation for early-season weed management. Furthermore, knowledge regarding the emergence patterns of common waterhemp and Palmer amaranth combined with monitoring environmental factors such as soil moisture and soil temperature may assist efforts for scouting fields to determine the likely presence of these weed species. The timing of viable postemergence herbicide options for control of glyphosate-resistant waterhemp and Palmer amaranth is critical and monitoring weather patterns to direct scouting efforts may improve the timeliness of these postemergence applications.

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23

Jordan, Kyle K. "The effects of landscaping mulch on invertebrate populations and soil characteristics." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1092784271.

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Sohrabinia, Mohammad. "Estimation of the near-surface air temperature and soil moisture from satellites and numerical modelling in New Zealand." Thesis, University of Canterbury. Geography, 2013. http://hdl.handle.net/10092/8707.

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Satellite observations provide information on land surface processes over a large spatial extent with a frequency dependent on the satellite revisit time. These observations are not subject to the spatial limitations of the traditional point measurements and are usually collected in a global scale. With a reasonable spatial resolution and temporal frequency, the Moderate Resolution Imaging Spectroradiometer (MODIS) is one of these satellite sensors which enables the study of land-atmospheric interactions and estimation of climate variables for over a decade from remotely sensed data. This research investigated the potential of remotely sensed land surface temperature (LST) data from MODIS for air temperature (Ta) and soil moisture (SM) estimation in New Zealand and how the satellite derived parameters relate to the numerical model simulations and the in-situ ground measurements. Additionally, passive microwave SM product from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) was applied in this research. As the first step, the MODIS LST product was validated using ground measurements at two test-sites as reference. Quality of the MODIS LST product was compared with the numerical simulations from the Weather Research and Forecasting (WRF) model. Results from the first validation site, which was located in the alpine areas of the South Island, showed that the MODIS LST has less agreement with the in-situ measurements than the WRF model simulations. It turned out that the MODIS LST is subject to sources of error, such as the effects of topography and variability in atmospheric effects over alpine areas and needs a careful pre-processing for cloud effects and outliers. On the other hand, results from the second validation site, which was located on the flat lands of the Canterbury Plains, showed significantly higher agreement with the ground truth data. Therefore, ground measurements at this site were used as the main reference data for the accuracy assessment of Ta and SM estimates. Using the MODIS LST product, Ta was estimated over a period of 10 years at several sites across New Zealand. The main question in this part of the thesis was whether to use LST series from a single MODIS pixel or the series of a spatially averaged value from multiple pixels for Ta estimation. It was found that the LST series from a single pixel can be used to model Ta with an accuracy of about ±1 ºC. The modelled Ta in this way showed r ≈ 0.80 correlation with the in-situ measurements. The Ta estimation accuracy improved to about ±0.5 ºC and the correlation to r ≈ 0.85 when LST series from spatially averaged values over a window of 9x9 to 25x25 pixels were applied. It was discussed that these improvements are due to noise reduction in the spatially averaged LST series. By comparison of LST diurnal trends from MODIS with Ta diurnal trends from hourly measurements in a weather station, it was shown that the MODIS LST has a better agreement with Ta measurements at certain times of the day with changes over day and night. After estimation of Ta, the MODIS LST was applied to derive the near-surface SM using two Apparent Thermal Inertia (ATI) functions. The objective was to find out if more daily LST observations can provide a better SM derivation. It was also aimed to identify the potential of a land-atmospheric coupled model for filling the gaps in derived SM, which were due to cloud cover. The in-situ SM measurements and rainfall data from six stations were used for validation of SM derived from the two ATI functions and simulated by the WRF model. It was shown that the ATI function based on four LST observations has a better ability to derive SM temporal profiles and is better able to detect rainfall effects. Finally, the MODIS LST was applied for spatial and temporal adjustment of the near-surface SM product from AMSR-E passive microwave observations over the South Island of New Zealand. It was shown that the adjustment technique improves AMSR-E seasonal trends and leads to a better matching with rainfall events. Additionally, a clear seasonal variability was observed in the adjusted AMSR-E SM in the spatial domain. Findings of this thesis showed that the satellite observed LST has the potential for the estimation of the land surface variables, such as the near-surface Ta and SM. This potential is greatly important on remote and alpine areas where regular measurements from weather stations are not often available. According to the results from the first validation site, however, the MODIS LST needs a careful pre-processing on those areas. The concluding chapter included a discussion of the limitations of remotely sensed data due to cloud cover, dense vegetation and rugged topography. It was concluded that the satellite observed LST has the potential for SM and Ta estimations in New Zealand. It was also found that a land-atmospheric model (such as the WRF coupled with the Noah and surface model) can be applied for filling the gaps due to cloud cover in remotely sensed variables.

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25

Sun, Jian. "Parameter estimation of coupled water and energy balance models based on stationarity constraints of soil moisture and temperature." Thesis, Boston University, 2012. https://hdl.handle.net/2144/31613.

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Thesis (Ph.D.)--Boston University PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. A new method is developed for estimating the parameters of land surface water and energy balance models through enforcement of stationary constraints on soil moisture and temperature. Through conditional averaging of the water balance equation with respect to soil moisture and the energy balance equation with respect to surface temperature, a measure of stationarity is derived that approximates the errors present in predicted fluxes (e.g. evaporation, runoff, sensible heat, ground conduction) in terms of measured model inputs (e.g. precipitation, radiation, soil moisture and temperature). Minimization of the approximated error yields estimates of model parameters. The approach is distinct from traditional model calibration because the minimized error term does not depend on measurements of the predicted fluxes. This proposed method is applied to a land surface water and energy balance model similar to those used in global climate models. The approach is tested at two Ameriflux sites with continuous in-situ measurements of soil moisture, temperature, radiation, and surface turbulent fluxes (evapotranspiration and sensible heat). Fluxes estimated with the proposed method match field measurements approximately as well as those estimated by traditional calibration. Replacing the in-situ land surface temperature and soil moisture with estimates retrieved from satellite leads to minimal degradation of model performance. Sensitivity analysis at these sites demonstrates that increasing model complexity does not improve performance. With promising results from testing the approach at these field sites, the method is applied to estimate evapotranspiration over the Southern Great Plains region of North America. In this test, archived meteorological data and remotely sensed moisture and temperature are used to force the model. The spatial pattern of estimated mean annual evapotranspiration is in good agreement (RMSE of 8 Wm-2 , R 2 of 0.75) with published estimates derived from measured precipitation and streamflow. Estimated parameters are reasonably distributed and consistent with climate and vegetation patterns over the region. Because there are so few sites on earth where surface turbulent fluxes are measured, the proposed approach is more widely applicable than traditional calibration methods, and thus could be used, with satellite data, to estimate maps of land surface parameters required by global climate models. 2031-01-01

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26

Baur, Florian [Verfasser], and George C. [Akademischer Betreuer] Craig. "Soil moisture-precipitation coupling over Central Europe : relative impact of surface heterogeneity on deep convection / Florian Baur ; Betreuer: George C. Craig." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2019. http://d-nb.info/1196009007/34.

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Hammer, Rachel Lynn. "Soil Respiration and Related Abiotic and Remotely Sensed Variables in Different Overstories and Understories in a High Elevation Southern Appalachian Forest." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/93272.

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Forests have the ability to sequester carbon from our atmosphere. Soil respiration (Rs) plays a role in a forest's ability to do so as it is a significant source of carbon dioxide back to the atmosphere. Therefore, understanding the process of Rs under varying conditions is gaining more attention. As of now we have a relatively good understanding of Rs under managed forest ecosystems such as pine plantations. This particular study examined Rs under different overstories and understories in a high elevation Southern Appalachian forest in order to get a better understanding of Rs under a natural hardwood system. The four vegetation types under consideration were an eastern hemlock (Tsuga canadensis L. Carriere) dominated overstory, a hardwood overstory with little to no understory, a mountain laurel (Kalmia latifolia L.) dominated understory, and a cinnamon fern (Osmundastrum cinnamomeum (L.) C.Presl) dominated understory. Differing temporal variations of Rs were observed under the vegetation types. We found monthly differences in rates among vegetation type however, an overall annual difference in Rs rates between vegetation types was not observed. This simply indicates the importance of observing Rs under different time scales to get a better understanding of its variation. We also calculated vegetation indices from remotely-sensed data to explore any relationships to Rs as well as if the indices themselves could improve out model. A vegetation index is a number that is calculated for every pixel in a remotely sensed image and represents plant vigor or abundance. Few significant relationships were found between the indices and Rs. Future work may want to better understand vegetation indices' spatial extent and accuracy in order to find whether they may be beneficial in Rs estimation. Understanding the influence of varying vegetation type and soil temperature and moisture on Rs will ultimately improve our ability to predict what drives changes in carbon fluxes. Master of Science Forests have the ability to sequester carbon from our atmosphere. Soil respiration (Rs) plays a role in a forest’s ability to do so as it is a significant source of carbon dioxide back to the atmosphere. Therefore, understanding the process of Rs under varying conditions is gaining more attention. As of now we have a relatively good understanding of Rs under managed forest ecosystems such as pine plantations. This particular study examined Rs under different overstories and understories in a high elevation Southern Appalachian forest in order to get a better understanding of Rs under a natural hardwood system. The four vegetation types under consideration were an eastern hemlock (Tsuga canadensis L. Carriere) dominated overstory, a hardwood overstory with little to no understory, a mountain laurel (Kalmia latifolia L.) dominated understory, and a cinnamon fern (Osmundastrum cinnamomeum (L.) C.Presl) dominated understory. Differing temporal variations of Rs were observed under the vegetation types. We found monthly differences in rates among vegetation type however, an overall annual difference in Rs rates between vegetation types was not observed. This simply indicates the importance of observing Rs under different time scales to get a better understanding of its variation. We also calculated vegetation indices from remotely-sensed data to explore any relationships to Rs as well as if the indices themselves could improve out model. A vegetation index is a number that is calculated for every pixel in a remotely sensed image and represents plant vigor or abundance. Few significant relationships were found between the indices and Rs. Future work may want to better understand vegetation indices’ spatial extent and accuracy in order to find whether they may be beneficial in Rs estimation. Understanding the influence of varying vegetation type and soil temperature and moisture on Rs will ultimately improve our ability to predict what drives changes in carbon fluxes.

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DAVIES, BERESFORD OBAFEMI ARNOLD. "A MODEL FOR THE PREDICTION OF SUBGRADE SOIL RESILIENT MODULUS FOR FLEXIBLE-PAVEMENT DESIGN: INFLUENCE OF MOISTURE CONTENT AND CLIMATE CHANGE." University of Toledo / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1102690606.

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Kong, Xin. "Near-surface soil moisture retrieval at field and regional scales in UK : coupling of field measurements, a dynamic model and satellite imagery." Thesis, University of East Anglia, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429801.

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30

Wennman, Pär. "Decomposition and nitrogen transformations in digested sewage sludge applied to mine tailings-effects of temperature, soil moisture, pH and plants /." Uppsala : Dept. of Soil Sciences, Swedish Univ. of Agricultural Sciences, 2004. http://epsilon.slu.se/9157666288.pdf.

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31

Ensor, Breanne Leigh. "Spatial and Temporal Trends in Greenhouse Gas Fluxes from a Temperate Floodplain along a Stream-Riparian-Upland Gradient." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/71424.

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Increased floodplain and wetland restoration activity has raised concerns about potential impacts on the release of greenhouse gases (GHGs) to the atmosphere due to restored connectivity between aquatic and terrestrial ecosystems. Research has shown GHG fluxes from hydrologically active landscapes such as floodplains and wetlands vary spatially and temporally in response to primary controls including soil moisture, soil temperature, and available nutrients. In this study, we performed a semimonthly sampling campaign measuring GHG (CO2, CH4, and N2O) fluxes from six locations within a third-order stream floodplain. Site locations were based on dominant landscape positions and hydrologic activity along a topographic gradient including a constructed inset floodplain at the stream margin, the natural levee, an active slough, the general vegetated floodplain, a convergence zone fed by groundwater, and the upland area. Flux measurements were compared to abiotic controls on GHG production to determine the most significant factors affecting GHG flux from the floodplain. We found correlations between CO2 flux and soil temperature, organic matter content, and soil moisture, CH4 flux and pH, bulk density, inundation period length, soil temperature, and organic matter content. But minimal correlations between N2O flux and the measured variables. Spatially, our results demonstrate that constructed inset floodplains have higher global warming potential in the form of CH4 than any other site and for all other GHGs, potentially offsetting the positive benefits incurred by enhanced connectivity. However, at the reach scale, total CO2 flux from the soil remains the greater influence on climate since the area covered by these inset floodplains is comparatively much smaller than the rest of the floodplain. Master of Science

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32

Boisserie, Marie. "Generation of an empirical soil moisture initialization and its potential impact on subseasonal forecasting skill of continental precipitation and air temperature." Tallahassee, Florida : Florida State University, 2010. http://etd.lib.fsu.edu/theses/available/etd-03112010-043112.

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Thesis (Ph. D.)--Florida State University, 2010. Advisor: James O'Brien, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page viewed on July 21, 2010. Document formatted into pages; contains xv, 90 pages. Includes bibliographical references.

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Schuh, Carina. "Influence of soil moisture content and infiltration on ground temperature and active layer depth in a river terrace in Adventdalen, Svalbard." Thesis, Stockholms universitet, Institutionen för naturgeografi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-121459.

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The active layer constitutes an important subsystem of permafrost environments. Thermal andhydrological processes in the active layer determine local phenomena such as erosion, hydrologicaland ecosystem changes, and can have implications for the global carbon-climate feedback.Despite their importance for environmental and climate change, active layer dynamics are stillonly poorly understood. The importance of hydrology for active layer processes is generallywell acknowledged on a conceptual level, but the physical interdependencies between soil moisture,subsurface water flows and active layer depth are largely unresolved. This thesis usedstate-of-the-art numerical modeling to study the influence of ground surface temperature, soilmoisture content and advective heat flow on near-surface permafrost temperatures and activelayer depths. The investigation was performed for a dry, loess-covered river terrace in centralAdventdalen, Svalbard, and fed by high-resolution hydro-climatic field data for the period2000-2014. Nine scenarios were considered in order to independently test the influence ofdifferent initial soil moisture contents (6%, 12%, and 19%) and infiltration patterns (no infiltration,constant infiltration, and early summer peak infiltration). Results indicated that the permafrost-hydrological system at the study site is largely influenced by cryosuction processes due tostrong capillarity of the highly unsaturated soil. Zones of increased ice content developedprimarily near the permafrost table, creating a ‘transition zone’ between the lower part of theactive layer and the upper permafrost. Infiltration based on snow melt and summer precipitationwas found to be negligible for the seasonal active layer development. The active layer depthgenerally decreased with increasing initial soil moisture content due to a higher consumption oflatent heat. However, cryosuction into the permafrost table and water percolation could potentiallycounterbalance latent heat effects, at least in systems characterized by higher soil moisturecontents. Both model simulations and field observations showed a clear tendency of increasingactive layer depth during the study period, whereas inter-annual variations in active layer depthwere comparably small. Given the moisture migration into the ‘transition zone’, the modelresults further suggested that the site might be capable to buffer thaw and thus obscure increasingground surface temperatures to a certain degree. This could have implications for the suitabilityof active layer depth as a proper indicator for climate change.

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Wu, Sihong. "Impact of cold climate on boreal ecosystem processes : exploring data and model uncertainties." Doctoral thesis, KTH, Biogeofysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-40451.

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The impact of cold climate on physical and biological processes, especially the role of air and soil temperature in recovering photosynthesis and transpiration in boreal forests, was investigated in a series of studies. A process-based ecosystem model (CoupModel) considering atmospheric, soil and plant components was evaluated and developed using Generalized Likelihood Uncertainty Estimation (GLUE) and detailed measurements from three different sites. The model accurately described the variability in measurements within days, within years and between years. The forcing environmental conditions were shown to govern both aboveground and belowground processes and regulating carbon, water and heat fluxes. However, the various feedback mechanisms between vegetation and environmental conditions are still unclear, since simulations with one model assumption could not be rejected when compared with another. The strong interactions between soil temperature and moisture processes were indicated by the few behavioural models obtained when constrained by combined temperature and moisture criteria. Model performance on sensible and latent heat fluxes and net ecosystem exchange (NEE) also indicated the coupled processes within the system. Diurnal and seasonal courses of eddy flux data in boreal conifer ecosystems were reproduced successfully within defined ranges of parameter values. Air temperature was the major limiting factor for photosynthesis in early spring, autumn and winter, but soil temperature was a rather important limiting factor in late spring. Soil moisture and nitrogen showed indications of being more important for regulating photosynthesis in the summer period. The need for systematic monitoring of the entire system, covering both soil and plant components, was identified as a subject for future studies. The results from this modelling work could be applied to suggest improvements in management of forest and agriculture ecosystems in order to reduce greenhouse gas emissions and to find adaptations to future climate conditions. QC 20110921 the Nitro-Europe project

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Roshani, Pedram. "The Effect of Temperature on the SWCC and Estimation of the SWCC from Moisture Profile under a Controlled Thermal Gradient." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31072.

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In many situations, the upper layers of soil above the ground water table are in a state of unsaturated condition. Although unsaturated soils are found throughout the world, they are predominant in arid or semi-arid regions. In these areas, the soil water characteristic curve (SWCC) which relates the water content to the matric suction could be used as key tool to implement the mechanics of unsaturated soils into the designs of geotechnical structures such as dams, embankments, pavements, canals, and foundations. Several experimental techniques are available for determining the SWCC in a laboratory environment. However, these experimental techniques are expensive, time consuming typically requiring days or weeks, depending on the soil type, and demanding intricate testing equipment. Due to these reasons, there has been a growing interest to find other means for estimating SWCC and encourage the adoption of unsaturated soils mechanics in geotechnical engineering practice. Several methods exist to indirectly estimate the SWCC from basic soil properties. Some may include statistical estimation of the water content at selected matric suction values, correlation of soil properties with the fitting parameters of an analytical equation that represents the SWCC, estimation of the SWCC using a physics-based conceptual model, and artificial intelligence methods such as neural networks or genetic programming. However, many studies have shown that environmental effects such as temperature, soil structure, initial water content, void ratio, stress history, compaction method, etc. can also affect the SWCC. This means that the estimation SWCC from set of conditions may not reliably predict the SWCC in other conditions. Due to this reason, it is crucial for engineers involved with unsaturated soils to take into account all the factors that influence the SWCC. The two key objectives of the present thesis are the development of a method based on first principles, using the capillary rise theory, to predict the variation of the SWCC as a function of temperature, as well as developing a technique for the prediction of the fixed parameters of a well-known function representing the SWCC based on basic soil properties together with the moisture profile of a soil column subjected to a known temperature gradient. A rational approach using capillary rise theory and the effect of temperature on surface tension and liquid density is developed to study the relation between temperature and the parameters of the Fredlund and Xing (1994) equation. Several tests, using a Tempe cell submerged in a controlled temperature bath, were performed to determine the SWCC of two coarse-grained soils at different temperatures. A good comparison between the predicted SWCC at different temperatures using the proposed model and the measured values from the Tempe cell test results is achieved. Within the scope of this thesis, a separate testing program was undertaken to indirectly estimate the SWCC of the same two coarse-grained soils from the measurement of their steady state soil-moisture profile while subjected to a fixed temperature differences. The water potential equation in the liquid and vapor phases is used to analyses the steady state flow conditions in the unsaturated soil. A good comparison is obtained for the SWCC estimated using this technique with the SWCC measured used a Tempe cell submerged in a controlled temperature bath. The results of this study indicate that knowledge of the moisture content of a soil specimen under a constant thermal gradient and basic soil properties can be used to estimate the SWCC of the soil at the desired temperature.

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36

Lloyd, Davidson A. "Effects of rhizosphere priming and microbial functions on soil carbon turnover." Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/9278.

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A major uncertainty in soil carbon studies is how inputs of fresh plant-derived carbon affect the turnover of existing soil organic matter (SOM) by so-called priming effects. Priming may occur directly as a result of nutrient mining by existing microbial communities, or indirectly via microbial population adjustments. Soil type and conditions may also influence the intensity and direction of priming effects. However the mechanisms are poorly understood. The objectives of this study were (1) to investigate how additions of labile C4 substrate affected SOM turnover in two contrasting unplanted C3 soils (clayey fertile from Temple Balsall, Warwickshire (TB) and sandy acid from Shuttleworth, Bedfordshire (SH) using13 C isotope shifts; (2) to investigate the influence of rhizodeposition from plant roots on SOM turnover in the same two soils planted with a C4 grass; (3) to assess an automated field system for measuring soil temperature, moisture and photosynthesis sensitivities of SOM turnover in the same two soils over diurnal to seasonal time scales. I used a combination of laboratory incubation, glasshouse and field experiments. In the soil incubation experiment, I made daily applications of either a maize root extract or sucrose to soil microcosms at rates simulating grassland rhizodeposition, and followed soil respiration (Rs) and its δ13 C over 19 days. I inferred the extent of priming from the δ13 C of Rs and the δ13 C of substrate and soil end-members. There were positive priming effects in both soils in response to the two substrates. In the SH soil there were no differences in priming effects between the substrates. However in the TB soil, sucrose produced greater priming effects than maize root extract, and priming effects with sucrose increased over time whereas with maize root extract declined after the first week. I explain these effects in terms of the greater fertility of the TB soil and resulting greater microbial nitrogen mineralization induced by priming. Because the maize root extract contained some nitrogen, over time microbial nitrogen requirements were satisfied without priming whereas with sucrose the nitrogen demand increased over time. In the glasshouse experiment, I planted C4 Kikuyu grass (Pennisetum clandestinum) in pots with the same two soils. The extent of rhizodeposition by the plants was altered by intermittently clipping the grass in half the pots (there were also unplanted controls) and priming effects were inferred from the δ13 C of Rs and the δ13 C of plant and soil end-members. Unclipped plants in both soils generated positive priming effects, while clipping reduced priming in TB soil and produced negligible PEs in SH soil. Microbial nutrient mining of SOM again explained the observed PEs in this experiment. Photosynthesis was a major driver of priming effects in the planted systems. In the third experiment, I found that the tested automated chamber system provided reliable measurements of Rs and net ecosystem exchange (NEE), and it was possible to draw relations for the dependency of Rs and NEE on key environmental drivers. Collectively, the results contribute to a better understanding of the mechanisms of priming effects and highlight possibilities for further research. The methods developed here will allow high temporal and spatial resolution measurements of Rs and NEE under field conditions, using stable isotope methods to separate fluxes into plant- and soil-derived components. Keywords: Soil respiration, soil moisture, soil temperature, Isotope ratio, maize root, flux chamber, climate change, organic matter, rhizodeposition.

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Sommerlot, Andrew Richard. "Coupling Physical and Machine Learning Models with High Resolution Information Transfer and Rapid Update Frameworks for Environmental Applications." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/89893.

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Few current modeling tools are designed to predict short-term, high-risk runoff from critical source areas (CSAs) in watersheds which are significant sources of non point source (NPS) pollution. This study couples the Soil and Water Assessment Tool-Variable Source Area (SWAT-VSA) model with the Climate Forecast System Reanalysis (CFSR) model and the Global Forecast System (GFS) model short-term weather forecast, to develop a CSA prediction tool designed to assist producers, landowners, and planners in identifying high-risk areas generating storm runoff and pollution. Short-term predictions for streamflow, runoff probability, and soil moisture levels were estimated in the South Fork of the Shenandoah river watershed in Virginia. In order to allow land managers access to the CSA predictions a free and open source software based web was developed. The forecast system consists of three primary components; (1) the model, which preprocesses the necessary hydrologic forcings, runs the watershed model, and outputs spatially distributed VSA forecasts; (2) a data management structure, which converts high resolution rasters into overlay web map tiles; and (3) the user interface component, a web page that allows the user, to interact with the processed output. The resulting framework satisfied most design requirements with free and open source software and scored better than similar tools in usability metrics. One of the potential problems is that the CSA model, utilizing physically based modeling techniques requires significant computational time to execute and process. Thus, as an alternative, a deep learning (DL) model was developed and trained on the process based model output. The DL model resulted in a 9% increase in predictive power compared to the physically based model and a ten-fold decrease in run time. Additionally, DL interpretation methods applicable beyond this study are described including hidden layer visualization and equation extractions describing a quantifiable amount of variance in hidden layer values. Finally, a large-scale analysis of soil phosphorus (P) levels was conducted in the Chesapeake Bay watershed, a current location of several short-term forecast tools. Based on Bayesian inference methodologies, 31 years of soil P history at the county scale were estimated, with the associated uncertainty for each estimate. These data will assist in the planning and implantation of short term forecast tools with P management goals. The short term modeling and communication tools developed in this work contribute to filling a gap in scientific tools aimed at improving water quality through informing land manager's decisions. PHD

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Silva, Elienai Ferreira da [UNESP]. "Variabilidade espaço-temporal da emissão de CO2 do solo em curto período sob influência de eventos de precipitação." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/138071.

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Submitted by ELIENAI FERREIRA DA SILVA null (elienay_ufal@yahoo.com.br) on 2016-04-20T13:13:56Z No. of bitstreams: 1 Dissertação_Elienai_Ferreira_da_Silva_2016.pdf: 3253667 bytes, checksum: e870c1f05f0e42c11842daaae32d27f1 (MD5) Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-04-26T14:57:01Z (GMT) No. of bitstreams: 1 silva_ef_me_jabo.pdf: 3253667 bytes, checksum: e870c1f05f0e42c11842daaae32d27f1 (MD5) Made available in DSpace on 2016-04-26T14:57:01Z (GMT). No. of bitstreams: 1 silva_ef_me_jabo.pdf: 3253667 bytes, checksum: e870c1f05f0e42c11842daaae32d27f1 (MD5) Previous issue date: 2016-02-26 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) A emissão de CO2 do solo (FCO2) em áreas agrícolas é um processo resultante da interação de diferentes fatores, tais como as condições de clima e solo. Nesse sentido, objetivou-se, com este estudo, investigar a variabilidade espaço-temporal da FCO2, temperatura (Tsolo), umidade (Usolo) e porosidade livre de água (PLA) do solo e suas interações, em área de reforma do canavial. O estudo foi conduzido em área de cana-de-açúcar sob reforma, na qual foi instalada malha amostral de 90 × 90 m2 contendo 100 pontos espaçados entre si em 10 m. Nestes pontos foram avaliadas a FCO2, Tsolo e Usolo em 10 avaliações ao longo de um período de 28 dias. Para as avaliações da FCO2, foi utilizado o sistema portátil LI-8100A. Concomitantemente à avaliação de FCO2, foram determinadas a Tsolo (termômetro integrante do sistema LI-8100A) e a Usolo (aparelho TDR). A emissão de CO2 e a Usolo foi maior no dia 276, com maior valor médio de 4,67 µmol m-2 s-1 e 31,75% em função das precipitações na área de estudo. Contrariamente os menores valor médios foram observados para PLA 19,17% e para a Tsolo 20,90 ºC. Os modelos de regressão linear utilizando somente a Usolo e a PLA explicaram 85% e 80%, respectivamente, da variabilidade temporal da FCO2, indicando que ao longo do tempo, a emissão de CO2 foi controlada pela variação do conteúdo de água e aeração do solo. Por outro lado, não foram encontrados modelos lineares ou quadráticos significativos (p>0,05) entre a FCO2 e a Tsolo. Os modelos ajustados para descrever a variabilidade espacial da FCO2, Tsolo, Usolo e PLA foram esféricos e exponenciais, sendo o modelo esférico predominante. Com exceção de alguns dias específicos, a partir dos mapas não foi possível a visualização de regiões características da área que indicassem um padrão de variabilidade espacial. Possivelmente o fato da amostragem ter sido conduzida em uma escala reduzida pode ter colaborado para um comportamento aleatório das variáveis no tempo. A variabilidade espaço-temporal da emissão de CO2, temperatura, umidade e a aeração do solo é afetada pelas precipitações na área de estudo, e pode ser dividida em três períodos: antes, durante e após as precipitações. Valores mais elevados da emissão de CO2 do solo são observados durante as precipitações e menores valores antes e pós-precipitações. Soil CO2 emission (FCO2) in agricultural areas is a process that results of the interaction of different factors such as climate and soil conditions. In this sense, the aim of this study was to investigate the spatial and temporal variability of FCO2, soil temperature (Tsoil), soil moisture (Msoil) and air-filled pore space (AFPS) and their interactions in a sugarcane field reform. This study was conducted in a 90 × 90- m sampling grid with 100 points spaced at distances of 10 m; at these points, 10 measurements were performed over a period of 28 days. In order to measure the FCO2, it was used a LI-8100A. Along with the measurements of FCO2, Tsoil and Msoil were also measured. It was observed an increase of 78% in FCO2 due to the rainfall in the study area. The linear regression models using only Msoil and AFPS explained 85% and 80%, respectively, of the variability of FCO2, indicating that over the time, the emission of CO2 was controlled by varying the content of water and soil aeration. The adjusted models to describe the spatial variability of FCO2, Tsoil, Msoil and AFPS were spherical and exponential. However, the spherical model was more predominant. We did not identify spatial variability using the maps for some days. Probably this happened because we used the small scale. It can have collaborated for random behavior. The spatiotemporal variability of CO2 emission, temperature, moisture and air-filled pore space was affected by rainfall in the study area. We can divide this variability in three periods: before, during and after rainfall. The higher values of CO2 emissions was observed during rainfall and lower values before and after rainfall.

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Panosso, Alan Rodrigo. "Variabilidade espacial da emissão de CO2, temperatura e umidade em latossolo sob cultivo de cana-de-açúcar em sistemas de colheita manual com queima e mecanizada /." Jaboticabal : [s.n.], 2006. http://hdl.handle.net/11449/88280.

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Resumo: A caracterizacao da variabilidade espacial de atributos do solo de areas agricolas e uma tarefa importante, pois somada a influencia dos aspectos pedologicos temos uma grande contribuicao do manejo. Neste trabalho foi determinada a estrutura da variabilidade espacial da emissao de CO2, temperatura e umidade em Latossolo Vermelho eutroferrico em tres localidades sob cultivo da cana-de-acucar em sistemas de manejos de cana crua e de cana queimada, no nordeste do Estado de Sao Paulo. As maiores emissoes foram observadas no local sob manejo de cana queimada, num valor medio de 2,05 Êmol m-2 s-1, porem dependencia espacial na emissao de CO2 foi encontrada somente nas areas sob manejo de cana crua. Os modelos de semivariancia foram exponenciais, esfericos e gaussianos sendo a dependencia espacial classificada como forte ou moderada em todos os casos. Os mapas de krigagem da emissao de CO2, temperatura e umidade do solo sob manejo de cana queimada mostraram correspondencia a declividade do terreno, com as maiores emissoes e temperaturas e menores umidades localizadas na parte mais alta do local estudado. Os resultados indicaram correlacao linear entre a emissao de CO2 com a temperatura e com a umidade do solo somente no local com manejo de cana queimada, e nao no sistema de cana crua, onde a presenca de palhada na superficie certamente impede a acao direta da radiacao solar e o escoamento de chuvas. Abstract: The characterization of spatial variability in agricultural soils is an important task, because added to the pedological aspects the soil management also influences such variability. In this work the spatial variability structure of a bare Dark Red Latosol CO2 emission, temperature and moisture were determined in three locations used with sugar cane crop culture, submitted to slash and burn or no till management systems in northeastern of Sao Paulo State. The highest emissions were observed in the slash and burn plot, with mean value of 2,05 Êmol m-2 s-1, but no spatial variability structure was seen for the CO2 emission in this plot. The variability models were exponential, spherical and gaussian, being the spatial dependence classified as strong and moderate in all the cases. In the slash and burn system, the kriging maps of soil CO2 emission, temperature and moisture had shown similarities to the land declivity, with the higher emissions and temperatures and the lower moisture values located in the highest parts of the studied place. The results indicated linear correlation between soil emission with temperature and moisture only in the slash and burn plot, and not in the no-till plots where crop residues were left in soil surface and certainly modified the direct action of the solar radiation and the rain draining. Orientador: Newton La Scala Júnior Coorientador: Gener Tadeu Pereira Banca: José Marques Júnior Banca: Marisa de Cássia Piccolo Mestre

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40

Cai, Tiebo. "Analysis of the net ecosystem exchange of CO₂ in a 56-year-old coastal Douglas-fir stand : its relation to temperature, soil moisture and photosynthetically active radiation." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/30753.

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The primary goal of this thesis was to investigate the relationship of canopy photosynthesis (P) to photosynthetically active radiation (PAR) in a 56-year-old coastal Douglas-fir stand (DF49) located on Vancouver Island. Canopy P was calculated as daytime NEP + daytime R[sub e], where NEP and R[sub e] are net ecosystem production of CO[sub 2] and ecosystem respiration, respectively. Half-hourly values of NEP were obtained using an EC (eddy covariance) system consisting of a 3-D sonic anemometer-thermometer and a closed-path infrared gas (CO[sub 2]/H[sub2]O) analyzer, and daytime R[sub e] was inferred by obtaining the intercept of the relationship between half-hourly values of NEP and PAR. Daytime R[sub e] thus obtained was approximately 71-75% of that calculated by applying the logarithmically-transformed relationship between nighttime NEE (-NEP) and soil temperature (T[sub s]) to daytime half hours. Values of R[sub 10] (the rate of R[sub e] at T[sub s] = 10 °C), obtained from both annual nighttime and daytime R[sub e] – T[sub s] relationships, increased linearly with increasing soil moisture when averaged over the active growing season (April 1 - Sept 30). However, the effect of soil moisture on R[sub e] shown on the multi-year scale could not be detected on the seasonal or annual scale probably as a result of the confounding effects of other environmental factors on R[sub e]. The effective PAR (Q[sub e]) contributing to canopy P in this Douglas-fir canopy was well described as Q[sub d0] + kQ[sub b0], with Q[sub d0] and Q[sub b0] being sky diffuse and direct PAR, respectively. The parameter k, which accounts for the total scattering of Q[sub b0] and the non-scattering effect (e.g., penumbral light spreading) of the solar rays, was found to be approximately 0.22 for this stand. While the Michaelis-Menten equation (the MM model) (i.e., P = αQ[sub t0])A[sub max]/(αQ[sub t0]+A[sub max]), where Q[sub t0] = Q[sub d0] + Q[sub b0]) results in significant overestimation of P in sunny conditions and significant underestimation of P in cloudy conditions, its modification into P = αQ[sub e])A[sub max]/(αQ[sub e]+A[sub max]) (the Q[sub e]-MM model) eliminated these systematic errors. When k = 1, the Q[sub e]-MM model reduces to the MM model. The Q[sub e] - MM model is a single big-leaf model, but it avoids the type of errors made in earlier generations of single big leaf models of canopy P, i.e., using APAR (the total absorbed PAR by the canopy) to calculate P. The simplicity of the Q[sub e]-MM model makes it convenient to be incorporated into large-scale carbon climate models. This study also shows that the widely used sun/shade model developed by de Pury and Farquhar (1997) is inadequate, mainly because the sun/shade model fails to account for the incidence angle between the solar beam and individual sunlit leaves. As with the P modeled using the MM model, the modeled P obtained using the sun/shade model has significant systematic errors with respect to Q[sub d0]/Q[sub t0] (the ratio of Q[sub d0] to Q[sub t0]). In contrast, using the Q[sub e]-MM model to estimate canopy P for this Douglas-fir stand eliminated these systematic errors with respect to Q[sub d0]/Q[sub t0]. In addition, the Q[sub e] -MM model developed in this study agrees with the detailed multilayer model of canopy P developed by Norman and Arkebauer (1991) for agricultural crops (i.e., soybean and corn). Land and Food Systems, Faculty of Graduate

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41

Panosso, Alan Rodrigo [UNESP]. "Variabilidade espacial da emissão de CO2, temperatura e umidade em latossolo sob cultivo de cana-de-açúcar em sistemas de colheita manual com queima e mecanizada." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/88280.

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Made available in DSpace on 2014-06-11T19:23:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-09-12Bitstream added on 2014-06-13T20:50:12Z : No. of bitstreams: 1 panosso_ar_me_jabo.pdf: 2194382 bytes, checksum: c6f96722456045aaddb9ac21be01b595 (MD5) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) A caracterizacao da variabilidade espacial de atributos do solo de areas agricolas e uma tarefa importante, pois somada a influencia dos aspectos pedologicos temos uma grande contribuicao do manejo. Neste trabalho foi determinada a estrutura da variabilidade espacial da emissao de CO2, temperatura e umidade em Latossolo Vermelho eutroferrico em tres localidades sob cultivo da cana-de-acucar em sistemas de manejos de cana crua e de cana queimada, no nordeste do Estado de Sao Paulo. As maiores emissoes foram observadas no local sob manejo de cana queimada, num valor medio de 2,05 Êmol m-2 s-1, porem dependencia espacial na emissao de CO2 foi encontrada somente nas areas sob manejo de cana crua. Os modelos de semivariancia foram exponenciais, esfericos e gaussianos sendo a dependencia espacial classificada como forte ou moderada em todos os casos. Os mapas de krigagem da emissao de CO2, temperatura e umidade do solo sob manejo de cana queimada mostraram correspondencia a declividade do terreno, com as maiores emissoes e temperaturas e menores umidades localizadas na parte mais alta do local estudado. Os resultados indicaram correlacao linear entre a emissao de CO2 com a temperatura e com a umidade do solo somente no local com manejo de cana queimada, e nao no sistema de cana crua, onde a presenca de palhada na superficie certamente impede a acao direta da radiacao solar e o escoamento de chuvas. The characterization of spatial variability in agricultural soils is an important task, because added to the pedological aspects the soil management also influences such variability. In this work the spatial variability structure of a bare Dark Red Latosol CO2 emission, temperature and moisture were determined in three locations used with sugar cane crop culture, submitted to slash and burn or no till management systems in northeastern of Sao Paulo State. The highest emissions were observed in the slash and burn plot, with mean value of 2,05 Êmol m-2 s-1, but no spatial variability structure was seen for the CO2 emission in this plot. The variability models were exponential, spherical and gaussian, being the spatial dependence classified as strong and moderate in all the cases. In the slash and burn system, the kriging maps of soil CO2 emission, temperature and moisture had shown similarities to the land declivity, with the higher emissions and temperatures and the lower moisture values located in the highest parts of the studied place. The results indicated linear correlation between soil emission with temperature and moisture only in the slash and burn plot, and not in the no-till plots where crop residues were left in soil surface and certainly modified the direct action of the solar radiation and the rain draining.

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42

Chavez, Luis Fernando. "Emissões de Co2 do solo sob preparo convencional e plantio direto em latossolo vermelho do Rio Grande do Sul." Universidade Federal de Santa Maria, 2008. http://repositorio.ufsm.br/handle/1/5476.

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Climatic change is associated with the increase of greenhouse gases (GHG) concentration, including carbon dioxide (CO2). Among the most important strategies to decrease global warming are decrease emissions and increase biological capture of CO2 through carbon sequestration in the ecosystems. Therefore, soils are fundamental to this strategy because depending in its use and management, they could act as a carbon source or sink. A study was conducted in a Rhodic Hapludox, in a long-term (22 years) experiment, to evaluate CO2-C emissions from soil produced by management practices and its dependence on soil temperature and moisture. CO2-C emissions were intensively analysed with two soil cameras, a dynamic camera (Licor-6400-09) fabricated by LI-COR Company and a static camera (PVC camera) during an evaluation period of 30 days. A intensive cropping system were used in both tillage systems. Results suggest that tillage systems produced differences in the CO2-C emission. No-till system had the highest CO2-C efflux from soil, being 22% higher than the conventional tillage. In conventional tillage highest peaks of CO2-C emissions were verified after soil tillage with disk harrow and chisel plow, nevertheless they were of short duration. CO2-C emissions were influenced by variations in soil temperature and moisture. Higher CO2-C emissions from soil in the no-till system were related to higher soil carbon stocks, presence of soybean residues in the surface, higher contents of particulate organic carbon and higher microbial biomass that together with the higher soil moisture compared to conventional tillage explained the higher efflux. The CO2-C efflux in the long-term no-till reflected the higher soil quality in this system. These results suggest that in the long-term no-till system due to high biologic activity and high soil moisture, soybean residues won t increase soil organic matter content. As mudanças climáticas contemporâneas estão sendo associadas ao aumento da concentração de gases de efeito estufa (GEE), entre eles o dióxido de carbono (CO2). Entre as estratégias para diminuir o aquecimento global destaca-se a diminuição das emissões e o incremento da absorção biológica de CO2 através do seqüestro de carbono em ecossistemas. Assim, os solos são fundamentais nessa estratégia uma vez que, dependendo do seu uso e manejo, podem ser um importante fonte ou sumidouro de carbono. Com o objetivo de avaliar as emissões de C-CO2 do solo causadas pelas práticas de manejo e sua dependência na temperatura e umidade do solo, desenvolveu-se um estudo em solo classificado como Latossolo Vermelho distrófico típico em experimento de longa duração (22 anos). As emissões de C-CO2 foram registradas e captadas com duas câmaras; uma dinâmica (Licor-6400-09) fabricada pela companhia LI-COR e outra estática (câmara de PVC) durante um período de avaliação de 30 dias. Os resultados demonstraram que os sistemas de preparo causaram diferenças na emissão de C-CO2 do solo e o plantio direto (PD) foi o que ocasionou o maior efluxo de CO2 do solo, sendo 22% superior ao preparo convencional (PC). Os maiores picos de emissões de C-CO2 foram verificados logo após o preparo do solo com arado e gradagem na parcela sob PC, porém tiveram curta duração. As emissões de C-CO2 foram influenciadas pelas variações da temperatura e umidade do solo, foi verificada correlação significativa (r=0,89) entre o fluxo de C-CO2 do solo e a temperatura do solo em PD, contrastando com o PC onde não houve correlação entre estas variáveis. As maiores emissões de C-CO2 do solo no PD foram relacionadas ao maior estoque de carbono, a presença de resíduos na superfície, a maior quantidade de carbono lábil e a maior biomassa microbiana que associados com maior umidade do solo explicam o efluxo, refletindo assim a maior qualidade do solo neste sistema. Os resultados sugerem que no PD de longa duração, devido à alta atividade biológica e altos conteúdos de umidade, os resíduos de soja não promoverão aumento de matéria orgânica do solo. As emissões de C-CO2 captadas com a câmara dinâmica foram correlacionadas significativamente com as emissões da câmara estática no PD. No entanto, não apresentaram relação no PC. Este projeto de pesquisa é o resultado de uma cooperação científica entre o grupo de pesquisa em Manejo do Solo da UFRGS, Departamento de Solos da UFSM e FUNDACEP.

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43

Khan, Shabana. "Factors affecting nitric oxide and nitrous oxide emissions from grazed pasture urine patches under New Zealand conditions." Lincoln University, 2009. http://hdl.handle.net/10182/1570.

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New Zealand is dominated by its agricultural industry with one of the most intensive farming practices being that of intensive dairying. New Zealand currently has approximately 5.3 million dairy cows that excrete up to 2.2 L of urine, per urination event, up to 12 times per day. This equates to 5.1 x10¹⁰ L per year or enough urine to fill over 1.2 million milk tankers. This sheer volume of urine and its associated N content has implications for the cycling of N within the pasture soils utilised, and New Zealand’s greenhouse gas budget due to the emission of N₂O from urine affected areas. The emission of nitric oxide (NO) from agricultural systems is also receiving increasing attention due to concerns about alterations in the balance of atmospheric trace gases and sinks. Worldwide there is a dearth of information with respect to the emissions of NO from urine-N deposition onto soils with only two in situ studies and no studies on the effects of soil pH, environmental variables or urine-N rate on NO fluxes. This present study has provided some fundamental information on the factors and processes affecting the emission of NO from bovine urine applied to pasture soils. Five experiments were performed in total; three laboratory experiments and two field experiments. The first laboratory experiment (chapter 4) examined the effect of the initial soil pH on NOx emissions from urine-N applied at 500 kg N ha⁻¹. Soil was treated to alter the initial soil pH over the range of 4.4 to 7.6. Initial soil pH affected rates of nitrification which in turn affected the decline in soil pH. Emissions of NO increased with increasing soil pH. However, a strong positive linear relationship was established between the NO-N flux, expressed as a percentage of the net NH4⁺-N depletion rate, and the level of soil acidity. The NO-N fluxes were higher under the more acidic soil conditions where N turnover was lower. The fluxes of N₂O did not follow the same pattern and were attributed to biological mechanisms. In experiment two (chapter 5) the objectives were to concurrently examine the effects of varying the soil temperature and the water-filled pore space (WFPS) on NOx emissions from urine-N. In this experiment increasing the soil temperature enhanced both the rate of nitrification and the rate of decrease in soil pH. The relationship between the net NO-N flux, expressed as a percentage of the net NH4⁺-N depletion rate, and the level of soil acidity was again demonstrated at the warmest soil temperature (22°C) where soil acidification had progressed sufficiently to enable abiotic NO formation. The NO-N fluxes increased with decreasing soil moisture and increasing soil acidity indicating abiotic factors were responsible for NO production. The Q10 response of the NO flux between 5 to 15°C decreased from 4.3 to 1.5 as WFPS increased from 11% to 87% respectively. Fluxes of N₂O increased with increasing WFPS and temperature indicating that denitrification was the dominant process. Results from experiments 2 and 3 indicated that the rate of nitrification had a direct bearing on the ensuing soil acidity and that it was this in conjunction with the available inorganic-N pools that affected NOx production. Therefore the third experiment examined the effect of urine-N rate on NOx emissions, with urine-N rate varied over 5 levels from 0 to 1000 kg N ha⁻¹, the highest rate being that found under maximal urine-N inputs to pasture. Rates of nitrification were diminished at the highest rates of urine-N applied and decreases in soil acidity were not as rapid due to this. Again significant but separate linear relationships were developed, for each urine-N rate used, between the NO-N flux, expressed as a percentage of the net NH4⁺-N depletion rate, and the level of soil acidity. The slope of these relationships increased with increasing urine-N rate. The NO-N flux, expressed as a percentage of the net NH4⁺-N depletion rate, versus soil acidity was higher under 1000 kg N ha⁻¹, despite the lower soil acidity in this treatment. This indicated that the enhanced inorganic-N pool was also playing a role in increasing the NO flux. The N₂O fluxes were of limited duration in this experiment possibly due to conditions being disadvantageous for denitrification. In the field experiments two urine-N rates were examined under both summer and winter conditions at two urine-N rates. The emission factors after 71 days for NO-N in the summer were 0.15 and 0.20% of the urine-N applied for the 500 and 1000 kg N ha⁻¹ rates respectively while the respective N₂O-N fluxes were 0.14 and 0.16%. Under winter conditions the emission factors after 42 days for NO-N were <0.001% of the urine-N applied regardless of urine-N rate while the N₂O-N fluxes were 0.05 and 0.09% for the 500 and 1000 kg N ha⁻¹ urine-N rates respectively. The relationships and predictors of NO-N flux determined in the laboratory studies did not serve as strong indicators of the NO-N flux under summer conditions. Low emissions from urine-N over winter were due to the low soil temperatures and high WFPS. These studies have demonstrated that soil chemical and environmental variables influence the production of NOx and N₂O emissions from urine-N applied to soil and that seasonal effects have a significant impact on the relative amounts of NO-N and N₂O-N emitted from urine patches. Suggestions for future work are also made.

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44

Ren, Junping. "Interpretation of the Frozen Soils Behavior Extending the Mechanics of Unsaturated Soils." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39555.

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Soil is the most widely used material in the construction of various civil infrastructure. Various types of soils are extensively used in its natural or compacted form in the construction of dams, canals, road and railway subgrades, and waste containment structures such as soil covers and liners. These infrastructure and foundation soils are exposed to the influence of environmental factors. In the permafrost and seasonally frozen regions, soils can be in different states (e.g., saturated or unsaturated, frozen or thawed, or combinations of them) due to the variations in moisture content and temperature. The soil-water characteristic curve (SWCC), which is the relationship between soil water content and suction, is used in the interpretation and prediction of unsaturated soils behavior. Similarly, the soil-freezing characteristic curve (SFCC), which is the relationship between unfrozen water content and subzero temperature, is used in the prediction and interpretation of frozen soils behavior. In this thesis, the SWCC and SFCC of two Canadian soils (i.e. Toronto silty clay (TSC) and Toronto lean clay (TLC)) were extensively investigated for better understanding the fundamental relationship between SWCC and SFCC. The soil resilient modulus (MR) is a key material property used in the rational design of pavements. Experimental investigations were undertaken to determine the MR of five Canadian soils (i.e., TSC, TLC, Kincardine lean clay (KLC), Ottawa Leda clay (OLC), and Indian Head till (IHT)), considering the influence of moisture and temperature, with the aid of an advanced triaxial testing equipment. Two simple models were proposed for estimating the MR of frozen soils, in this thesis. In addition, an artificial neural network (ANN) model was developed for estimating the MR of the five Canadian soils considering various influencing factors. The conclusions from the various studies in this thesis are succinctly summarized below. (1) Four expressions (i.e. power relationship, exponential relationship, van Genuchten equation, and Fredlund and Xing equation) that are widely used for representing the SFCC were selected for providing comparisons between the measured and fitted SFCCs for different soils. The results suggest that the exponential relationship and van Genuchten equation are suitable for sandy soils. The power relationship reasonably fits the SFCC for soils with different particle sizes, but not for saline silts. The Fredlund and Xing equation is flexible and provides good fits for all the soils. (2) The SFCC and SWCC of TSC and TLC were experimentally determined, analyzed, and compared. Many factors influence the reliable measurement of SFCC, which include sensors’ resolution and stability, sensor calibration for each soil, and thermodynamic equilibrium condition. The hysteresis of SFCC for the two soils is mainly attributed to the supercooling of pore water. The quantitative dissimilarity in the measured SFCC and SWCC may be attributed to specimen structure variations during compaction and saturation, and during freezing / thawing processes, and cracks formation due to sensors insertion. In addition, some fundamental differences may exist between the drying / wetting and freezing / thawing processes, resulting in dissimilarity. (3) Two novel models were proposed for the estimation of MR of frozen soils. The semi-empirical model extends the mechanics of unsaturated soils and employs SFCC for prediction. Several coarse- and fine-grained saturated soils were used to validate this model. The empirical hyperbolic model was proposed considering that the frozen MR versus subzero temperature relationship resembles hyperbola. This model was validated on coarse- and fine-grained soils under saturated / unsaturated conditions. The hyperbolic model has wider application since it can be used for both saturated and unsaturated frozen soils. Both the models are simple and promising. (4) The MR of five Canadian soils subjected to wetting and freezing was determined by using the GDS ELDyn triaxial testing system. A freezing system was established for controlling the desired testing temperatures within the soil specimens. The results suggest: (i) The effect of subzero temperature on the MR is significant. (ii) For TLC, KLC, OLC, and IHT, the frozen MR versus subzero temperature relationship of the saturated specimen typically has steeper slope than specimen at the optimum water content, for the temperature range from 0 to -5 °C. (iii) The effect of stress levels on the frozen MR depends on soil type, water content, and subzero temperature. Lastly, (iv) Loading frequency does not show a significant influence on the frozen MR. (5) The MR of the five Canadian soils was determined considering wetting and freeze-thaw (F-T) conditions. The results suggest: (i) The F-T cycles result in weak soil structure due to reduction in suction, particles movement, loss of cohesion, and formation of cracks / channels. (ii) The critical numbers of F-T cycles were determined as 1, 1, 2, and 1 for TLC, KLC, OLC, and IHT at the optimum water content, respectively. (iii) The percentage of reduction in MR after the critical number of F-T cycles was strongly related to the plasticity index for specimens tested at the optimum water content. (iv) The wetting process results in the decrease in suction and enlargement of soil pores. Consequently, relatively low MR values were measured at high water contents, and the effect of F-T cycles becomes insignificant. Finally, (v) The effect of stress levels on the MR was dependent on the initial water content of the specimen and soil type.

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45

Malbéteau, Yoann. "Suivi des ressources en eau par une approche combinant la télédétection multi-capteur et la modélisation phénoménologique." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30193/document.

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Ces travaux ont pour objectif général d'améliorer la représentation spatio-temporelle des processus hydrologiques de surface à partir de modèles dont la complexité est adaptée aux informations disponibles par la télédétection multi-capteur/multi-résolution. Nous avons poursuivi des développements méthodologiques (désagrégation, assimilation, modélisation du bilan d'énergie) autour de l'estimation de l'humidité du sol dans le contexte de la gestion des ressources en eau dans les régions semi-arides. Récemment, des missions spatiales permettent d'observer l'humidité des sols en surface; notamment avec le capteur AMSR-E (Advanced Microwave Scanning Radiometer-EOS) et la mission SMOS (Soil Moisture Ocean Salinity). Toutefois la résolution spatiale de ces capteurs est trop large (> 40 km) pour des applications hydrologiques. Afin de résoudre le problème d'échelle, l'algorithme de désagrégation DisPATCh (Disaggregation based on Physical and Theoretical Scale Change) a été développé en se basant sur un modèle d'évapotranspiration. Dans la première partie de thèse, l'algorithme est appliqué et validé sur le bassin du Murrumbidgee (sud-est de l'Australie) avec une résolution spatiale cible de 1 km à partir des données de LST (Température de surface) et NDVI (indice de végétation) issues de MODIS (MODerate resolution Imaging Spectroradiometer) et de deux produits d'humidité du sol basse résolution : SMOS et AMSR-E. Les résultats montrent que la désagrégation est plus efficace en été, où la performance du modèle d'évapotranspiration est optimale. L'étude précédente a notamment mis en évidence que la résolution temporelle des données DisPATCh est limitée par la couverture nuageuse visible sur les images MODIS et la résolution temporelle des radiomètres micro-ondes (3 jours pour SMOS). Dans la deuxième partie, une nouvelle approche est donc développée pour assurer la continuité temporelle des données d'humidité de surface en assimilant les données DisPATCh dans un modèle dynamique de type force-restore, forcé par des données météorologiques issus de ré-analyses, dont les précipitations. La méthode combine de manière originale un système variationnel (2D-VAR) pour estimer l'humidité du sol en zone racinaire et une approche séquentielle (filtre de Kalman simplifié) pour analyser l'humidité du sol en surface. La performance de l'approche est évaluée sur deux zones: la région Tensift-Haouz au Maroc et la région de Yanco en Australie. Les résultats montrent que le couplage désagrégation/assimilation de l'humidité du sol est un outil performant pour estimer l'humidité en surface à l'échelle journalière, même lorsque les données météorologiques sont incertaines. Dans la troisième partie, une méthode de correction des effets topographiques sur la LST est développée dans le but d'étendre l'applicabilité de DisPATCh aux zones vallonnées ou montagneuses qui jouent souvent le rôle de château d'eau sur les régions semi-arides. Cette approche, basée sur un modèle de bilan d'énergie à base physique, est testée avec les données ASTER (Advanced Spaceborne Thermal Emission Reflection Radiometer) et Landsat sur la vallée d'Imlil dans le Haut Atlas Marocain. Les résultats indiquent que les effets topographiques ont été fortement réduits sur les images de LST à ~100 m de résolution et que la LST corrigée pourrait être utilisée comme une signature de l'état hydrique en montagne. Les perspectives ouvertes par ces travaux concernent la correction/désagrégation des données de précipitations et l'estimation des apports par l'irrigation pour une gestion optimisée de l'eau This thesis aims to improve the spatio-temporal resolution of surface water fluxes at the land surface-atmosphere interface based on appropriate models that rely on readily available multi-sensor remote sensing data. This work has been set up to further develop (disaggregation, assimilation, energy balance modeling) approaches related to soil moisture monitoring in order to optimize water management over semi-arid areas. Currently, the near surface soil moisture data sets available at global scale have a spatial resolution that is too coarse for hydrological applications. Especially, the near surface soil moisture retrieved from passive microwave observations such as AMSR-E (Advanced Microwave Scanning Radiometer-EOS) and SMOS (Soil Moisture and Ocean Salinity) data have a spatial resolution of about 60 km and 40 km, respectively. In this context, the downscaling algorithm "DISaggregation based on Physical And Theoretical scale Change" (or DisPATCh) has been developed. The near surface soil moisture variability is estimate within a low resolution pixel at the targeted 1 km resolution based on an evapotranspiration model using LST (Land surface temperature) and NDVI (vegetation index) derived from MODIS (MODerate resolution Imaging Spectroradiometer) data. Within a first step, DisPATCh is applied to SMOS and AMSR-E soil moisture products over the Murrumbidgee river catchment in Southeastern Australia and is evaluated during a one-year period. It is found that the downscaling efficiency is lower in winter than during the hotter months when DisPATCh performance is optimal. However, the temporal resolution of DisPATCh data is limited by the gaps in MODIS images due to cloud cover, and by the temporal resolution of passive microwave observations (global coverage every 3 days for SMOS). The second step proposes an approach to overcome these limitations by assimilating the 1 km resolution DisPATCh data into a simple dynamic soil model forced by reanalysis meteorological data including precipitation. The original approach combines a variational scheme for root-zone soil moisture analysis and a sequential approach for the update of surface soil moisture. The performance is assessed using ground measurements of soil moisture in the Tensift-Haouz region in Morocco and the Yanco area in Australia during 2014. It is found that the downscaling/assimilation scheme is an efficient approach to estimate the dynamics of the 1 km resolution surface soil moisture at daily time scale, even when coarse scale and inaccurate meteorological data including rainfall are used. The third step presents a physically-based method to correct LST data for topographic effects in order to offer the opportunity for applying DisPATCh over mountainous areas. The approach is tested using ASTER (Advanced Spaceborne Thermal Emission Reflection Radiometer) and Landsat data over a 6 km by 6 km steep-sided area in the Moroccan Atlas. It is found that the strong correlations between LST and illumination over rugged terrain before correction are greatly reduced at ~100 m resolution after the topographic correction. Such a correction method could potentially be used as a proxy of the surface water status over mountainous terrain. This thesis opens the path for developing new remote sensing-based methods in order to retrieve water inputs -including both precipitation and irrigation- at high spatial resolution for water management

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46

Souza, Luma Castro de [UNESP]. "Emissão de CO2 do solo associada à escarificação em latossolo e em argissolo." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/149881.

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Submitted by LUMA CASTRO DE SOUZA null (lumasouza30@hotmail.com) on 2017-03-22T13:39:12Z No. of bitstreams: 1 Luma_Castro_de_Souza.pdf: 1962132 bytes, checksum: d9f166261796c44cf5d9fa2c419999e6 (MD5) Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-03-22T19:35:40Z (GMT) No. of bitstreams: 1 souza_lc_dr_jabo.pdf: 1962132 bytes, checksum: d9f166261796c44cf5d9fa2c419999e6 (MD5) Made available in DSpace on 2017-03-22T19:35:40Z (GMT). No. of bitstreams: 1 souza_lc_dr_jabo.pdf: 1962132 bytes, checksum: d9f166261796c44cf5d9fa2c419999e6 (MD5) Previous issue date: 2017-03-16 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) A operação de escarificação altera a estrutura do solo, afetando a dinâmica da emissão de CO2 do solo em curto período de tempo. Assim, com este estudo, objetivou-se: i - investigar a variação temporal da emissão de CO2 do solo após escarificação para o plantio da cana-de-açúcar em Latossolo e em Argissolo; ii - caracterizar a emissão de CO2, associada à distribuição de poros, em Latossolo e em Argissolo, submetidos à escarificação na linha de plantio e escarificação em área total para o plantio da cana-de-açúcar. O delineamento experimental utilizado foi em parcelas grandes pareadas. Os tratamentos utilizados consistiram na escarificação na linha de plantio (ELP) e escarificação em área total (EAT), em Latossolo e em Argissolo, localizados nos municipios de Guariba e Monte Alto, respectivamente. Para atender ao primeiro objetivo, avaliaram-se a emissão de CO2, a temperatura do solo (Tsolo) e a umidade do solo (Usolo) ao longo de 12 dias no Latossolo e em 11 dias no Argissolo, na camada de 0-0,10 m de profundidade. No Latossolo, não foi observado correlação entre a emissão de CO2, tanto com a Usolo como para Tsolo. No Argissolo, a emissão de CO2 foi correlacionada à Usolo, tanto no solo sob ELP (R2 = 0,86) quanto no solo sob EAT (R2 = 0,58). As emissões totais de CO2 no período de estudo foram maiores no Latossolo, no solo sob escarificação em linha de plantio e em área total (ELP = 1,042.6 kg CO2 ha-1 e EAT = 1,336.3 kg ha-1 de CO2), e menores no Argissolo (ELP = 659,1 kg CO2 ha-1 e EAT = 702,8 kg CO2 ha-1). No Latossolo, a emissão de CO2 foi menor no solo sob preparo com escarificação somente na linha de plantio do que no solo sob preparo com escarificação em área total. No Argissolo, a emissão de CO2 não diferiu em função do preparo. Para atender ao segundo objetivo, além de avaliar a emissão de CO2, temperatura e umidade do solo, avaliaram-se também a distribuição do tamanho de poros, o carbono orgânico associado aos minerais (COAM) e o carbono orgânico particulado (COP) na camada de 0-0,10 m de profundidade. No Latossolo, somente as propriedades: emissão de CO2, COP e classe de poro C4 (ɸ ≤ 0,04 mm) diferiram em função da escarificação. O modelo de regressão múltipla explicou 72% da variabilidade da emissão de CO2 no solo submetido a ELP para o COAM e C2 (0,05 < ɸ ≤ 0,1 mm). No Argissolo, a emissão de CO2, temperatura, umidade do solo, COAM, COP e as classes de tamanho de poros não diferiram em função das escarificações. Na regressão múltipla, a umidade do solo, C1 (ɸ ≥ 0,1 mm) e o COAM explicaram, juntas, 82% da variabilidade da emissão de CO2 no solo sob ELP. No Latossolo, a escarificação em linha de plantio e em área total afetaram diretamente a estrutura do solo, causando mudanças na porosidade e alterações na emissão de CO2 do solo. No Argissolo, a escarificação em linha de plantio e em área total não afetaram a emissão de CO2. The chiseling operations alters the soil structure and affects the dynamics of the soil CO2 emission in a short period of time. Thus, the aim of this study was to: i- Investigate the temporal variation of CO2 emission after chiseling for the planting of sugarcane in Latossolo and Argissolo, ii – Characterize and correlation the soil CO2 emission and pore distribution in Latossolo and Argissolo with chiseling at line and total area to sugarcane planting. The experimental design used was in paired large plots. The treatments consisted of chiseling at the planting line (ELP) and chiseling at total area (EAT) in Latossolo and Argissolo, located in the municipalities of Guariba and Monte Alto, respectively. In order to attend the first aim, the CO2 emission, temperature and soil moisture were observed for 11 and 12 days, respectively at Argissolo and Latossolo, in the 0-0.10 m depth layer. The Latossolo did not show relationship among CO2 emission, Usoil and Tsoil to both chiseling. However, the Argissolo showed a significant relationship between the CO2 emission and Usoil to both chiseling, ELP (R2 = 0.86) and EAT (R2 = 0.58). The total CO2 emission was higher at Latossolo in both chiseling (ELP = 1,042.6 kg CO2 ha-1 and EAT = 1,336.3 kg ha-1 CO2) when compared with the Argissolo (ELP = 659.1 kg CO2 ha-1 and EAT = 702.8 kg CO2 ha-1). In the Latossolo, CO2 emission was lower in the soil under preparation with chiseling only in the planting line than in the soil under preparation with chiseling in the total area. In the Argissolo, the CO2 emission did not differ according to the preparation. In order to attend the second aim, the CO2 emission, temperature and soil moisture were also observed. Moreover, the distribution of pores size, organic carbon associated with minerals (COAM) and particulate organic carbon (COP) were also evaluated, in the 0-0.10 m depth layer. To Latossolo, the CO2 emission, COP and the distribution of pores size (C4; ɸ ≤ 0.04 mm) had significate difference between the chiseling. The multiple regression model was able to explain 72% of the CO2 emission variability to COAM and C2 (0.05 <ɸ ≤ 0.1 mm) at soil under ELP. To Argissolo, the CO2 emission, temperature, soil moisture, COAM, COP and distribution of pores size were not different between the chiseling. The soil moisture, C1 (ɸ ≥ 0,1 mm) and COAM were able to explain 82% of CO2 emission variability at soil under ELP. Therefore, the chiseling affected the soil porosity and soil CO2 emission directly at Latossolo. However, the chiseling did not affect the soil CO2 emission at Argissolo.

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47

Falkenberg, Nyland Ray. "Remote sensing for site-specific management of biotic and abiotic stress in cotton." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/478.

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This study evaluated the applicability of remote sensing instrumentation for site- specific management of abiotic and biotic stress on cotton grown under a center pivot. Three different irrigation regimes (100%, 75%, and 50% ETc) were imposed on a cotton field to 1) monitor canopy temperatures of cotton with infrared thermometers (IRTs) in order to pinpoint areas of biotic and abiotic stress, 2) compare aerial infrared photography to IRTs mounted on center pivots to correlate areas of biotic and abiotic stress, and 3) relate yield to canopy temperatures. Pivot-mounted IRTs and IR camera were able to differentiate water stress between the irrigation regimes, however, only the IR camera was effectively able to distinguish between biotic (cotton root rot) and abiotic (drought) stress with the assistance of groundtruthing. The 50% ETc regime had significantly higher canopy temperatures, which were reflected in significantly lower lint yields when compared to the 75% and 100% ETc regimes. Deficit irrigation up to 75% ETc had no impact on yield, indicating that water savings were possible without yield depletion.

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48

Cline, Nathan Lyle. "Wet-Thermal Time and Plant Available Water in the Seedbeds and Root Zones Across the Sagebrush Steppe Ecosystem of the Great Basin." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4384.

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Following wildfires, plant materials are direct-seeded to limit erosion and annual weed invasion. Seedlings often fail to establish because selected plant materials are not always well adapted to local soil moisture and temperature conditions. In an effort to help improve plant materials selection and to evaluate sites potential revegetation, we have worked toward developing methodology to predict germination and root growth based on site specific soil moisture and temperature conditions. First, we characterized the seedbed environment of 24 sagebrush (Artemisia spp.) steppe sites throughout the Intermountain West to determine the wet-thermal time of five temperature ranges relevant to germination response and thermal-time model accuracy (Chapter 1). Second, we predicted potential germination for 31 plant materials at those same sites (Chapter 2). Third, in preparation to predict root growth at multiple sites, we characterized the drying patterns and the associated plant-available water for in the seedling root zone across nine woodland (Juniperus spp. and Piñus spp.) sites (Chapter 3). For all of these studies, we determined the effects of tree reduction and tree infilling phase at time of tree reduction. Our key findings are that seedbeds generally sum most wet-thermal time at temperature ranges where the germination rates fit thermal accumulation models quite well (R2 ≥ 0.7). The majority of plant materials summed enough wet-thermal time for a potential germination at most sites during the fall, early spring, and late spring. Soil drying primarily occurs from the soil surface downward. Drying rates and Plant available water associated with the first drying event increased with increasing soil depth. Root zone (1-30 cm) plant-available water increased before and decreased after the first spring drying event with increasing soil depth. Tree removal with increasing pretreatment tree infilling phase generally added progress toward germination, plant available water, and wet-thermal time in the seedbed and root zones of the sagebrush steppe in the Great Basin. Because soil moisture and temperature does not appear to be limiting for potential germination, combining germination and root growth models to create a more comprehensive model may allow for a more robust prediction for seedling survival. For either root growth or combined germination and root growth models, plant available water and wet-thermal time before the first spring drying period hold the most potential for successfully predicting seedling survival.

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49

SILVA, José Roberto Lopes da. "Investigação da dinâmica dos processos hidrológicos e sedimentológicos em escala de parcela no semiárido de Pernambuco." Universidade Federal Rural de Pernambuco, 2015. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/5317.

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Submitted by Mario BC (mario@bc.ufrpe.br) on 2016-08-15T12:47:57Z No. of bitstreams: 1 Jose Roberto Lopes da Silva.pdf: 3751979 bytes, checksum: d1e5aa84305eb1d047e5f172594d52cf (MD5) Made available in DSpace on 2016-08-15T12:47:58Z (GMT). No. of bitstreams: 1 Jose Roberto Lopes da Silva.pdf: 3751979 bytes, checksum: d1e5aa84305eb1d047e5f172594d52cf (MD5) Previous issue date: 2015-07-28 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq Financiadora de Estudos e Projetos - Finep The semiarid region of Brazilian Northeast is characterized by presenting spatio-temporal variability of meteorological and hydrological variables, and in recent years comes to checking an increase of degraded areas in the region because of intensive soil use and absence of conservation practices. The inappropriate use of soil associated with climate change is unleashing and accelerating desertification processes. The characterization of the dynamics of hydrological and sedimentological processes in these regions become essential, since there is great shortage for a database in the semiarid watersheds that can support the management of water resources and soil conservation and provide subsidies for the use of models and generate future scenarios. Within this context the present research aims to evaluate the efficiency of conservation practices alternative and low cost in reducing soil loss and water as well as in maintaining soil moisture and dynamic surface temperature, through the investigation of hydrological and sedimentological processes in plot scale under different conditions of use and vegetation cover in semiarid region, in order to subsidize actions for the management and conservation of water and soil. The research was conducted in the County of Pesqueira, Agreste region of Pernambuco. Moisture dynamics, water loss and soil were evaluated in the following conditions of use: Plot with Natural Cover (PCN), Plot with Bare Soil (PD), Plot with Barrier of forage Palm (PBP) and Plot with Mulching (PCM). The results showed that the use of mulching as compared to bare soil promoted reduction of soil surface temperature during the day and increase overnight. The mulch was effective in reducing runoff and erosion control. The use of the barrier with forage palm was efficient in reducing soil loss, and proved to be a promising technique for conservation region. Among the conditions of covers evaluated the plot with bare soil was the one with the higher correlation between precipitation and runoff. In general the portion with forage palm (PBP) had moisture levels above the other treatments, showing to be a catchment system in situ efficient for the evaluated local conditions, mainly after the establishment of rain. The temporal stability of the moisture has been identified, and the stable points correlated well with the global average, with coefficients of determination (R²) above 0.90, the same can be used accurately to estimate soil moisture measurements in future. The Hydrus-1D model was able to simulate successfully moisture dynamics in the soil over time for the conditions of bare soil and natural cover, at a depth of 20 cm. Based on the analyzed period database it has been possible to present monthly values of soil moisture reference to investigated conditions, and thus subsidize studies of hydrological and sedimentological modeling in the region. A região semiárida do Nordeste Brasileiro é caracterizada por apresentar variabilidade espaço-temporal das variáveis meteorológicas e hidrológicas, e nos últimos anos vem-se verificando um aumento de áreas degradadas na região em função do uso intensivo do solo e ausência de práticas de conservação. O mau uso do solo associado às variações climáticas vem desencadeando e acelerando os processos de desertificação. A caracterização da dinâmica dos processos hidrológicos e sedimentológicos nessas regiões tornam-se essenciais, uma vez que existe grande carência de um banco de dados em bacias hidrográficas do semiárido, que possam dar suporte à gestão de recursos hídricos e a conservação do solo, e fornecer subsídios para utilização de modelos e geração de cenários futuros. Dentro deste contexto a presente pesquisa visa avaliar a eficiência das práticas conservacionistas alternativas e de baixo custo na redução da perda de solo e água, bem como na manutenção da umidade do solo e dinâmica de temperatura superficial, através da investigação dos processos hidrológicos e sedimentológicos em escala de parcela sob diferentes condições de uso e cobertura vegetal em região semiárida, a fim de subsidiar ações voltadas para o manejo e conservação da água e do solo. A pesquisa foi desenvolvida no Município de Pesqueira, região Agreste do Estado de Pernambuco. A dinâmica de umidade, as perdas de água e solo foram quantificadas nas condições de: Parcela com Cobertura Natural (PCN), Parcela com solo Descoberto (PD), Parcela com Barramento de Palma forrageira (PBP) e Parcela com Cobertura Morta (PCM). Os resultados encontrados mostraram que o uso da cobertura morta em comparação ao solo descoberto promoveu redução da temperatura da superfície do solo durante o dia e acréscimo durante a noite. A cobertura morta foi eficiente na redução do escoamento superficial e no controle da erosão. O uso do barramento com palma forrageira apresentou eficiência na redução da perda de solo, e mostrou ser uma técnica conservacionista promissora para a região. Dentre as condições de coberturas avaliadas, a parcela com solo descoberto foi a que apresentou a maior correlação entre a precipitação e o escoamento superficial. De forma geral a parcela com barramento de palma forrageira (PBP) apresentou níveis de umidade acima dos demais tratamentos, mostrando-se ser um sistema de captação in situ eficiente para as condições locais avaliadas, principalmente após o estabelecimento da chuva. A estabilidade temporal da umidade foi identificada, e os pontos estáveis apresentaram boa correlação com a média global, com coeficientes de determinação (R²) superiores a 0,90, podendo os mesmos ser utilizados de forma precisa na estimativa da umidade do solo em medições futuras. O modelo Hydrus-1D foi capaz de simular de forma satisfatória a dinâmica de umidade no solo ao longo do tempo para as condições de solo descoberto e cobertura natural, na profundidade de 20 cm. Com base no banco de dados do período analisado foi possível apresentar valores mensais de referência da umidade do solo para condições investigadas, e desta forma subsidiar estudos de modelagem hidrológica e sedimentológica na região.

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50

Drouet, Emeline. "Impact de la température sur la carbonatation des matériaux cimentaires : prise en compte des transferts hydriques." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2010. http://tel.archives-ouvertes.fr/tel-00618092.

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La carbonatation est une pathologie du béton armé qui peut engendrer la corrosion des armatures et à terme de la fissuration. Dans le cadre de la gestion des déchets radioactifs, les structures et les conteneurs seraient soumis simultanément à un échauffement (exothermie des déchets), au CO2 atmosphérique, ainsi qu'à un séchage important. Afin de rendre compte de leur évolution à l'échelle séculaire, les données actuelles relatives à la carbonatation à température ambiante doivent être complétées, d'une part par une description de la phénoménologie en température, et d'autre part, par la prise en compte de l'impact des transferts hydriques en température (séchage) sur la carbonatation en insaturé. Le travail présenté se focalise sur l'étude de la durabilité de quatre pâtes de ciment différentes dont deux sont directement dérivées des formulations de référence sélectionnées par l'Andra (CEM I et CEM V) et un mélange baspH. Le premier volet est dédié à l'étude des transferts hydriques reposant sur la conduite d'essais de désorption. Il a notamment permis la caractérisation des isothermes de désorption en température (20, 50et 80°C). L'impact thermique modifie les isothermes : la teneur en eau à l'équilibre chute avec la température et le point d'amorçage de la condensation capillaire est déplacé. Une phase de modélisation a conjointement été conduite en support aux expérimentations. L'utilisation de l'équation de Clausius-Clapeyron a permis de décrire l'effet de la température sur les isothermes (par la détermination de la chaleur isostérique d'adsorption de chacun des matériaux). Bien que l'impact de la température sur la microstructure des pâtes de ciment soit avéré, la prise en compte du déplacement des équilibres thermodynamiques suffit à restituer cet effet thermique sur les isothermes. La détermination des perméabilités intrinsèques par exploitation des cinétiques de désorption (par analyse inverse) a montré la thermoactivation du transport d'eau. La contribution de l'évolution de la microstructure en température ne peut-être négligée sur la perméabilité des matériaux.Le deuxième volet exploratoire, est consacré à l'étude de la carbonatation en température. Il repose sur la mise en place d'un dispositif de carbonatation spécifique (fonctionnement en température) et la conduite d'essais de carbonatation à HR et température contrôlées. La campagne de caractérisation (DRX et ATG)a conduit à l'obtention de profils de carbonatation caractéristiques de chaque couple (HR, Température).Les évolutions minéralogiques (décomposition des hydrates, distribution polymorphique du carbonate de calcium précipité) mises en évidence en température se rapprochent de celles identifiées à température ambiante. En revanche, il ressort que les conditions environnementales influencent significativement les proportions polymorphiques : plus l'HR est faible, plus les teneurs en phases métastables (vatérite,aragonite) sont élevées. Les réactions de dissolution-précipitation mises en jeu dans la transformation polymorphique (des états métastables vers la calcite) sont inhibées à faible HR, par manque de milieu réactionnel. La cinétique de carbonatation, également impactée par les conditions environnementales, est régie par la concurrence de l'effet thermique sur les transferts hydriques et sur la solubilité rétrograde des réactifs. Les profondeurs carbonatées sont maximales aux points d'amorçage de la condensation capillaire propres aux différents matériaux et à chaque température. Les profondeurs carbonatées augmentent avec la température jusqu'à une température limite, caractéristique de la formulation, au-delà de laquelle la solubilité rétrograde des réactifs deviendrait le facteur limitant.Cette phase de compréhension des mécanismes mis en jeu dans la carbonatation en température et de leur niveau de couplage effectuée, les modèles prédictifs de carbonatation en insaturé pourront être étendus à l'application en température. Les résultats de ce travail fournissent les données d'entrées et de validation nécessaires à la validation des simulations numériques.

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Tesis sobre el tema "Soil Moisture Temperature Coupling"

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