Dissertations / Theses: 'Ecophysiology of soil microbes'

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Pietikäinen, Janna. "Soil microbes in boreal forest humus after fire." Helsinki : University of Helsinki, 1999. http://ethesis.helsinki.fi/julkaisut/maa/mekol/vk/pietikainen/.

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Manuel, Theodore Llewellyn. "Effect of soil nutrient status on stress tolerance in Proteaceae." Bachelor's thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/25615.

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Protea lepidocarpodendron grown on low, medium and high nutrient treatments exhibited the lowest, and similar evapotanspiration rates respectively over a 9 day water stress cycle (experimental period). In stressed and unstressed treatments, stomatal conductance and transpiration rates of plants grown on the low nutrient treatment was generally lower than that of plants grown on the medium and high nutrient treatments where stomatal conductance and transpiration rates were similar. Stressed plants grown on the low, medium and high nutrient treatments exhibited the lowest, intermediate and highest photosynthetic rates respectively. Stessed plants grown on the medium and high nutrient treatments exhibited a dramatic decrease in transpiration rates ands stomatal conductance from day 5 to 7, and a dramatic decrease in photosynthetic rates from day 3 to 7. Stressed plants grown on the low nutrient treatment showed a far less dramatic decrease in transpiration rate, stomatal conductance and photosynthetic rate over the 9 day period. For stressed plants, photosynthetic rates varied between 0.08-5.39 uMOLm⁻²s⁻¹, 1.17-7.48uMOlm⁻²s⁻¹ and 1.15-8.65uMOLm⁻²s⁻¹ for plants grown on low, medium and high nutient treatments respectively. Unstressed plants grown on low. medium and high nutrient treatments exhibited the lowest, highest and intermediate photosynthetic rates respectively. In all stressed treatments, photosynthetic rates showed a steady decline from day 1 to day 7, whereafter a dramatic increase occurred in the medium and high nutrient treatments, and a less dramatic increase in plants grown on the low nutrient treatment. These decreases and increases in photosynthetic rates was not parallelled in the stomatal conductance and transpiration rates of the unstressed plants. For unstressed plants, photosynthetic rates varied between 1.4s-4.4 uMOLm⁻²-s⁻¹, 1.65-6.7 uMOLm⁻²s⁻¹ and 3.42-8.76 uMoLm⁻²s⁻¹ for plants grown on low, medium and high nutrient treatments respectively. Plants grown on low nutrient treatments exhibited the highest LSW (182.3 gm⁻²), highest whole plant mass (WPM) (1.07g), followed by high (LSW=1.76 gm⁻²,WPM=0.83g) and medium (LSW=167.28 gm⁻² ,WPM=0.79g) nutrient treatments. Total plant nitrogen content was inversely related to LSW and WPM on low (3.84 mgNplant⁻¹), high (4.18 mgNplant⁻¹) and medium (5.28 mgNplant⁻¹) treatments. Root : ratio between treatments were similar.

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Thomson, Serena K. "Spatial scaling of soil microbes under different land uses." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/74239/.

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There has been an increasing emphasis placed on understanding microbial c, in order to enable the patterns and processes governing the spatial distribution of soil microbiota to be determined. Due to current food security issues, this is particularly important within agricultural systems given the fundamental role microorganisms play in the maintenance of crop health and productivity. With evidence in favour of both ubiquity and endemism, complicated by systems, scales and communities, there is a need to address the question of microbial biogeography within a single system. A range of field experimental resources were used to investigate factors controlling the assembly of soil microbial communities. Microorganisms across all three domains of life demonstrated spatial scaling, in which there was no single universal driver. Land-use management was an important driver of eukaryote distribution, but also impacted the drivers of bacterial and eukaryote taxa groups under land-use practice. When considering microbial community structure, a pan microbial relationship between abundance and distribution was shown for the first time, across all microbial groups. Furthermore, partitioning microbial communities into common and rare groups provided information on the processes operating on the community and highlighted the importance of land-use management for shaping the structure of communities. Finally, a case study on plasmodiophorids increased current estimates of plasmodiophorid diversity in the soil. Also different communities were associated with the rhizosphere compared with the bulk soil, under different hosts. Plant development stage was also an important consideration acting on this previously understudied but highly significant group of protists to crop health.

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Murray, R. R. "Degradation of chlordane, carbofuran and paraquat by soil microbes." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 1993. http://digitalcommons.auctr.edu/dissertations/3720.

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This study tested the degradative ability of the microbes in a silage microbial mat, two strains of exotic red bacteria and two strains of Pseudomonas spp. isolated from pesticide-treated soil. The microbes were challenged with carbofuran, paraquat and chlordane as a single pesticide or as a pesticide mixture. At 21 days, residual pesticide was extracted from the soil using EPA method 808OA. The extract was analyzed via HPLC, GC/MS and a toxicity bioassay. Radiolabelled carbofuran was used to determine the final destination of the pesticide. The results confirmed that the microbes were able to degrade all pesticides to some extent and that the absence of microbes resulted in no degradation.

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Knight, Bruce Philip. "Heavy metal speciation and bioavailability to microbes." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243803.

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Ahmed, Engy. "The interaction between microbes, siderophores and minerals in podzol soil." Licentiate thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-89319.

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Alogaidi, Faez Fayad Mohammed. "Understanding rice and soil phosphorus interactions with an emphasis on rice genetics and soil microbes." Thesis, University of Aberdeen, 2013. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=203870.

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Rice is the staple food for nearly one half of the ever growing world's population. Phosphorus (P) deficiency commonly constrains crop productivity on a large area of arable land worldwide. P fertilizer is a finite resource and an expensive input, so it must be used efficiently. The main objective of this study was to investigate plant and soil P interaction in P deficient conditions and understand plant mechanisms that could enhance P uptake efficiency throughout two main research approaches: Firstly, investigating plant and soil microbes' interaction that promotes plant growth in Plimited conditions. Secondly, evaluating the P uptake efficiency of a number of rice genotypes in a high throughput screening systems in order to understand genotypic variations in P uptake mechanisms. The genotypes used were genotyped for the allelic variation in the Pup1 locus and the effect of this QTL on the plant growth was also investigated. In an experiment investigating the influence of soil microbes on rice growth in P deficient conditions, an experimental system where pots were filled with a mix of 95% low P Insch subsoil and 5% Insch topsoil, where the subsoil was sterilized by autoclaving and the top soil was either sterilized or live. Non-autoclaved (live) topsoil caused a significant increase in shoot dry weight (SDW) for IAC 25 compared to autoclaved soil while the opposite was true for Azucena suggesting that the presence of soil microbes is needed for IAC 25 to access soil-bound P under P-limiting condition while for Azucena it is not. Most importantly, a very strong cultivar x treatment interactions on almost all growth parameters and elements in the shoot except for Mn were found. In a dose experiment investigating whether there is a general toxic effect for autoclaving Insch topsoil being used in this study on the growth of IAC 25, a strong positive correlations of plant growth parameters with the percentage of sterile topsoil vi levels were observed indicating that the autoclaved topsoil was not toxic. The influence of soil wash (distilled water added to the soil then extracted) and different types of soil as sources of inocula on the plant growth of rice cultivars were also studied. Soil wash inoculation did not affected plant growth but soil inocula increased the biomass of all rice cultivars (Azucena, IAC 25 and Lemont) tested suggesting that if it is microbes that are important they must be remaining in the soil and are not transferable by washing. Two autoclaved soils did not behave similarly in terms of affecting plant growth of rice cultivars (Azucena and IAC 25). Moreover, the live treatment of a new soil stimulated the growth of both cultivars and the cultivar x treatment interaction that was found in earlier experiment was lost with the use of this new soil. The implication is that the cultivar by autoclave treatment interaction is soil specific. The fluctuating results between the experiments indicate that it is unlikely that such studies can be extended into plant genetics. So, the second approach of the study focused on examining simpler plant/soil P interaction in P limiting conditions. A 25/75% subsoil/sand mix was determined as a P deficient and used to screen 30 rice genotypes in two experiments: the first when watered with Yoshida's nutrient solution (YNS) either with (YNS+P) or without P (YNS-P) to assess whether rice genotypes differ in extracting P added in liquid form while the second was designed to test if shallow and deep-rooted genotypes differ in extracting P present in soil by using rock phosphate in three treatments: when rock P was absent or embedded either in a shallow 10 cm layer or distributed homogenously in soil mix. For both experiments, P treatment x genotype interaction was significant on SDW. On average, YNS-P treatment significantly reduced the SDW for genotypes compared to that of plants grown in YNS+P treatment while the addition of rock phosphate greatly stimulated plant growth where SDW of plants grown in homogenous P and shallow P significantly outgrew vii those in zero P treatment. In both experiments, rice from the aus subgroup grown in -P treatment accumulated significantly more SDW than indica and japonica genotypes. In -P treatment, the genotypes that accumulated higher SDW relative to the others were Black Gora, Rayada, Kasalath, Azucena, IAC 25, Dom Sufid, Aux1Wild type, FR 13A and especially Sadu Cho. In the rock phosphate experiment, both P treatment and genotype affected RDW and root/shoot ratio significantly. Most importantly, two root angle traits (the mean root direction and the weighted average of the unsigned root angles) measured in rhizotrons were correlated with the relative SDW in shallow P (SDW in shallow P/SDW in zero P) slightly stronger than with relative SDW in homogenous P (SDW in homogenous P/SDW in zero P) indicating that the relationship between plant growth and root distribution with depth was altered by the distribution of rock phosphate in soil. In both experiments, the presence of Kasalath alleles in the Pup1 QTL significantly increased SDW of the genotypes. However, some genotypes, especially Dom Sufid and Sadu Cho performed well in these experiments despite lacking the Pup1 allele suggesting that Pup1 QTL is not the only determinant for tolerance to P deficiency. The system appears to be suitable for high throughput screens of rice genotypes.

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Canarini, Alberto. "Drought Effects on Soil Carbon Stability Mediated by Rhizodeposition and Microbes." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/15963.

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Drought will increase in frequency and intensity in many areas of the world and has the potential to turn entire ecosystems from a sink to a source of C. Soil represents one of the largest C pools on earth, and small changes in the balance between inputs and outputs may have extreme consequences for total atmospheric CO2 concentrations. Outputs are determined by microbial decomposition of soil organic matter (SOM) which can be divided in pools of different inherent stability and turn-over. A major stable pool of C is represented by organo-mineral complexes (C bound to silt and clay), which is primarily controlled by plant-derived inputs to soil and soil microbes. Drought effects on plants, microbes and their interactions could cause changes to the stable pool of C, however information on this topic is lacking. In this thesis I: (i) reviewed and quantified drought-induced effects on soil respiration and microbial communities by meta-analysis; (ii) quantified the effects of drying and rewetting on wheat-derived C stabilization and N cycling; (iii) quantified and qualified drought-induced effects on root exudation of soybean and sunflower; (iv) examined drought effects to C stabilization in the field. Results show that drought can induce intense losses of C by increasing soil respiration following rewetting. Highest losses were produced in combination of intense drought and C-rich soils. At the same time drying and rewetting can cause intense stress on plants, reducing biomass and C inputs to soil. However plants can adopt different strategies to drought-induced changes which are reflected in different rates and quality of root exudates. In field drought did not change the size of the mineral-associated or more stable soil C, highlighting resistance of grassland soils. Specific microbial groups were linked to stable soil C at different depths and legumes were shown to be a key functional group in mediating drought effects and increasing stable C in soil.

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Weinstein, Richard Neil. "Ecophysiology of fungi isolated from soil in an Antarctic fellfield ecosystem." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624489.

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Clark, Benjamin Robert. "Studies on the chemistry of Australian microbes /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe.pdf.

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Hariharan, Janani. "Predictive Functional Profiling of Soil Microbes under Different Tillages and Crop Rotations in Ohio." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1435856176.

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Kempster, Valerie N. "Soil microbes as potential control agents for plant-parasitic nematodes in pasture /." Title page, contents and summary only, 2000. http://web4.library.adelaide.edu.au/theses/09ACP/09acpk32.pdf.

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Weber, Eva. "Ecological insights into unexplored Archaea through environmental ecophysiology, single-cell genomics and cultivation." Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=231673.

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Carson, Christine Michelle. "Grassland soil microbial responses to long-term management of N availability." Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/36228.

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Master of Science Department of Biology Lydia H. Zeglin Anthropogenic actions have significantly increased biological nitrogen (N) availability on a global scale. In tallgrass prairies, this phenomenon is exacerbated by land management changes, such as fire suppression. Historically, tallgrass prairie fire removed N through volatilization, but fire suppression has contributed to increased soil N availability as well as woody encroachment. Because soil microbes respond to N availability and plant growth, these changes may alter microbial composition and important microbially-mediated functions. Grassland management affects the soil environment on multiple time scales including short (fertilization or fire event), seasonal (growing vs. non-growing season), and long-term (decadal plant turnover and nutrient accumulation), therefore my goal was to understand community variability at different time scales affecting the population and community dynamics of soil microbes. I predicted soil microbes would be sensitive to environmental changes at all time scales, seasonal variation would reflect increased plant rhizodeposit-supported populations during summer and decomposers during winter, and long-term fire suppression and chronic fertilization would drive soil microbial community turnover associated with accumulation of plant litter and N. To address these predictions, soils were collected from the Belowground Plot Experiment (BGPE) at Konza Prairie Biological Station: a 30-y factorial field manipulation of N fertilization and burning. Surface soils (0-15 cm) were sampled monthly between Nov 2014 – Dec 2015, including one week post-fire (April) and post-fertilization (June). Genomic DNA was extracted from each sample for qPCR and PCR for Illumina MiSeq library sequencing of the prokaryotic 16S rRNA gene and fungal ITS, to estimate population and community dynamics of soil microbes. Soil environmental characteristics and plant communities were measured in July 2015 to evaluate correlations between plant and microbial communities, and environmental variability. Soil microbial responses to short-term fire/fertilization events were minimal, while microbial population sizes fluctuate seasonally and synchronously, and microbial community composition varied more with management history than at shorter time scales. Bacterial populations increased 10x during growing-season plant rhizodeposition, while fungal populations were less dynamic, but decreased in fall, possibly reflecting a shift to subsistence on soil organic matter. In contrast, microbial community composition was seasonally stable, but distinct between long-term management treatments, which may indicate accumulation of niche-defining plant or soil properties over decades. Prokaryotic communities responded to altered N availability via both fertilization and loss due to fire, with the highest abundance of "copiotrophic" (r-selected) taxa in unburned, fertilized soils. Fungal communities responded to N fertilization with higher abundance of arbuscular mycorrhizal fungi, pathogens, and saprotrophs, possibly due to changes in nutrient stoichiometry and litter availability in fertilized plots. However, fungal response to fire was largely independent of N availability, and plant community differences were correlated with fungal, but not bacterial, community composition, highlighting the likely nutritional codependence of fungi and plants, and fungal competitive advantages for plant litter substrates. The timing of changes in soil microbial communities is critical for plant nutrition and nutrient cycling in prairies, and this novel dataset on the temporal resolution of microbial responses to environmental variability contributes to the broader understanding of ecosystem responses to global change.

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Harris, Sue-Re. "Phosphorus sensitivity in species of Proteaceae (Protea obtusifolia, Leucadendron coniferum and Leucadendron salignum) from different soil habitats : possible candidates for growth on former agricultural soils high in P." Bachelor's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/26186.

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The phosphorus (P) uptake capacities and tolerance to high P of three Proteaceae species from acid (Leucadenron coniferum, Leucadendron salignum) and alkaline (Protea obtusifolia, Leucadedndron meridianum) soils in the Cape Floristic Region (CFR) were compared. These species were also investigated as potential candidates for growth on nutrient enriched, post-agricultural soils. In parallel, two crop plant species (Lupinus albus, with cluster roots; and L. angustifolius, without cluster roots) were also compared. The cluster-root forming species (L. albus) was more sensitive to higher P levels and showed toxicity in terms of photosynthesis, efficiency of PSII, transpiration and stomatal conductance. Growth, gaseous exchange and efficiency of photosystem II (as a measure of stress) were determined at 1, 10 and 100 μg P g⁻¹ sand for both lupins and Proteaceae. Kinetics of P uptake (in hydroponics) was determined at a range ( 4 to 2000 μM P) of P concentrations. Phosphorus sensitivity was relatively high in Ld. coniferum as evident from reduced growth, net photosynthetic rate, stomata} conductance and transpiration rates. Protea obtusifolia showed the least sensitivity to increased phosphorus concentrations under acidic and native alkaline conditions. The inability to regulate P uptake rates at elevated phosphorus concentrations and excessive P accumulation were major determinants of P sensitivity. The relatively higher P sensitivity of Lupinus albus compared to L. angustifolius is likely related to the efficient P uptake by cluster roots in the former.

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Tang, Li. "The responses of soil microbes to climatic and anthropological factors in the Tibetan grasslands." Thesis, Griffith University, 2021. http://hdl.handle.net/10072/406524.

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It is widely known that soil microbes play an important role in biogeochemical cycling, affecting plant growth, and creating soil structure. Faced with the widespread global changes, unravelling the response of soil microbes is essential for understanding soil feedbacks to climate changes. Therefore, there is an increasing interest in studying soil microbial diversity patterns from local to global spatial scales and in investigating changes in soil microbial community diversity and community structure under global changes. However, how soil microbial communities would be altered by natural environmental changes and/or by human induced environmental changes are still not well understood at the regional scale. The Tibetan plateau is known as ‘the third pole’ because of its high elevation of over 4000 m above sea level. Ecosystems in the Tibetan plateau, dominated by alpine grasslands, are fragile and vulnerable to global changes. The increase rate of air temperature is up to three times the global average level. However, we still lack knowledge on responses of soil microbial community to climate gradient and human-induced environmental changes, e.g. climate warming and grazing. This thesis investigated changes in bacterial and fungal community diversity, composition, and co-occurrence along a hydrothermal gradient in the Tibetan plateau grasslands, and the interactive effects of climate changes (warming) and human activities (grazing) on soil microbial functional communities. Specifically, this thesis includes four experiments: Experiment 1 studied the changes in soil bacterial community along an environmental gradient in the Tibetan plateau. The hypothesis was that alpha diversity of soil bacterial community would increase with higher precipitation and air temperature. We therefore selected sampling sites distributed in main grassland types in the Tibetan plateau. Microbial DNA extracted from soil samples were subjected to the next-generation sequencing to characterize soil bacterial diversity and community. Meanwhile, information of environmental factors 44 was also collected to clarify the driving forces of changes in soil bacterial communities. These factors included mean manual precipitation (MAP), mean manual temperature (MAT), soil moisture (SM), elevation, soil total organic carbon (SOC), total nitrogen (TN), soil carbon: nitrogen ratio (C/N), available phosphorus (AP), soil pH, plant richness, plant aboveground biomass (plant BiomassA), plant belowground biomass (plant BiomassB), NH4+-N, NO3--N, dissolved organic carbon (DOC), soil dissolved organic nitrogen (DON), soil microbial biomass carbon (MBC) and nitrogen (MBN). We used statistical methods including simple correlation, multivariable analysis and structural equation modelling (SEM) to elucidate spatial pattern and the relative importance of biotic and abiotic factors in structuring soil bacterial communities. In the SEM, climate factors were expected to affect soil microbial communities through their influences on plant and soil properties. Main findings included: in terms of overall bacterial diversity, the swamp meadow with better water conditions had significantly higher diversity than other habitat types, while the alpine desert had the lowest diversity. The overall alpha diversity was significantly correlated with factors that can indicate soil nutrient status including total soil organic carbon, total nitrogen, plant aboveground biomass, nitrate nitrogen (N) and other factors. The effect of environmental factors on the overall bacterial community structure variation was greater than that of spatial factors. The effects of mean annual precipitation (MAP) on soil bacterial alpha diversity were mostly indirect through affecting soil dissolved organic carbon (DOC) and plant richness based on the SEM. Among the environmental factors, the most influential factor for the differences of bacterial community structure was MAP. Unlike the effects on bacterial alpha diversity, MAP had a strong direct effect on soil bacterial community structure. Other factors such as soil DOC and soil pH affected soil bacterial community structure directly without through mediating intermediate variables. By contrast, mean annual 68 temperature (MAT) was not significantly related to soil bacterial diversity or community composition. Experiment 2 studied soil fungal community of the same soil samples as described in Experiment 1. We hypothesized that there would be a close association between soil fungal community diversity/composition and plant community diversity or composition. The main findings were: Ascomycetes were the most abundant phylum in all samples (84.56%), followed by Basidiomycetes and the Zygomycota. Significantly positive correlation between the relative abundance of Ascomycota and precipitation was found, while the relative abundance of Glomeromycota was not significantly correlated with precipitation. Based on the best-fitting regression model, the most important predictors of fungal species richness were pH and plant species richness. MAP also had substantial effects on soil fungal richness, mostly through its effects on soil pH and plant richness. Environmental factors and geographic distance can independently explain partial changes of fungal community structure with a higher effect by environmental factors. Compared to strong direct effects of soil pH, MAP affected soil fungal community composition by altering soil pH and plant community structure based on structural equation modeling (SEM). Experiment 3 studied the microbial co-occurrence network along the transect as described in Experiment 1 and 2 by integrating soil bacterial and fungal community data. In this study, Spearman correlation-based network was constructed, and a set of network topological properties were calculated. In addition, the impact factors of network properties were also investigated. The main findings were: The microbial network size of alpine meadows was greater than that of the alpine steppes. However, the modularity of alpine steppe was higher compared to alpine meadow. In addition, networks of alpine steppe had a larger average path length. Based on these differences in network topological features, soil microbial communities of alpine steppe were considered more stable under environmental interferences. 93 Fungal networks were found to have larger modularity, but smaller inter-nodes connectivity compared with bacterial networks. Although betweenness centrality of bacterial nodes was higher in the alpine meadows, degree centrality was higher in the alpine steppes. The regional meta-network (integrating bacterial and fungal taxa) structure was mostly related to MAP. However, the network topological features of alpine meadows and alpine steppe were driven by different factors. MAP and soil moisture were the significant impact factors for alpine steppe network but not for alpine meadow. The network of alpine meadows was strongly associated with plant factors including biomass and diversity. Besides, fungal networks were not associated with plant community factors, but related to climate factors and soil properties, suggesting that drivers of soil fungal network were different from that of fungal community diversity and structure. In Experiment 4, we investigated the effects of warming, grazing and their interaction in a factorial warming (+1.2-1.7 oC) and grazing (moderate intensity with ca. 50% vegetation consumption) experiment in a Tibetan alpine meadow on soil microbial communities by studying functional genes involved in soil carbon and nitrogen cycles. We hypothesize that warming would interact antagonistically with grazing to affect soil microbial functional communities. In this study, soil microbial communities were analysed by Geochip and environmental parameters including temperature, soil properties and plant communities were also collected. The main findings include: microbial functional gene structure and abundances were largely affected by the interactive effect of grazing and warming, rather than the main effect of warming or grazing. Compared to the control, grazing alone significantly increased the functional gene alpha diversity, changed the overall functional community structure, and increased the abundances of C fixation, C degradation, N mineralization and denitrification genes, likely due to the stimulating impact of urine and 118 dung deposition. Warming alone did not change these microbial properties, possibly related to the unchanged soil nutrient status. Despite an increase in soil NO3- concentrations and the deposition of urine and dung, the combined warming and grazing treatment did not change functional gene alpha diversity, community structure, or C/N cycling gene abundances. Our study revealed antagonistic interactions between warming and grazing on microbial functional gene structure and abundances, which remained stable under moderate intensity of grazing in a future warming scenario in the Tibetan alpine meadow. In sum, this thesis indicated that diversity, composition, and inter-taxa association of soil microbial communities are sensitive to environmental changes in the Tibetan plateau grassland. Climate changes and human activities affected soil microbial communities through direct and indirect pathways. More importantly, the evaluation of microbial-mediated processes in the Tibetan Plateau grasslands should take interactions between climate changes and anthropogenic activities into account. Thesis (PhD Doctorate) Doctor of Philosophy (PhD) School of Environment and Sc Science, Environment, Engineering and Technology Full Text

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Macrae, Andrew. "Rhizobacterial ecology using 16S rRNA approaches." Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391289.

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Phophe, Paulina Avhavhudzani. "Carbon sequestration in cultivated and uncultivated Vachellia karroo sites in Tankwa Karoo National Park." University of Western Cape, 2021. http://hdl.handle.net/11394/8327.

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Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol) The Succulent Karoo Biome (SKB) in South Africa is widely reputed to house Earth’s greatest diversity of succulent plants. It is also famous for spectacular displays of annual flowers after good rains. The area experiences winter rainfall which infrequently exceeds 100 mm per annum but certain parts of the SKB can get 250 mm. Irrigated agriculture on a large scale was therefore not a viable option when European farmers began colonizing the land. The land was conquered from the indigenous Khoekhoe herders and San hunter-gatherers, South Africa’s first peoples. The biome underwent extreme transformation in the last 200 years following colonisation which resulted in homogenization of the landscape and extinction of many succulents thus reducing biodiversity.

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Bray, Sarah Renee. "Interactions between plants and soil microbes in Florida communities implications for invasion and ecosystem ecology /." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010945.

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Olivier, Charl Francois. "An investigation into the degradation of biochar and its interactions with plants and soil microbial community." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/17944.

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Thesis (MScAgric)--Stellenbosch University, 2011. ENGLISH ABSTRACT: Biochar (charcoal) is lauded by many scientists as an effective way to remove carbon dioxide from the atmosphere and storing it in a very stable form in the soil for hundreds to thousands of years, whilst promoting soil fertility and productivity. Considering that no significant amounts of charcoal are presently accumulating in the environment, despite considerable amounts produced globally in natural and man-made fires, this study focuses on understanding the degradation of biochar and its interactions with plants and soil organisms. The following experiments were conducted to achieve this goal. Controlled chemical oxidation of biochar, using different concentrations of hydrogen peroxide, was conducted in an attempt to mimic the enzymatic degradation of biochar by basidiomycetes. The changes occurring in biochars structure and chemistry were assessed afterwards. Furthermore, aerobic and anaerobic digestion of biochar was conducted in vitro, and in vivo to investigate the changes occurring in biochar‘s elemental composition and chemistry during oxidation and factors that play a determining role in the rate of biochar degradation. The influence of biochar in soil on free-living and symbiotic microbial communities as well as its impact on total plant biomass production and root development was assessed in three greenhouse pot trials using wheat and green beans as test plants It was proven that biochar is almost fully H2O2-degradable, mostly through hydroxylation and carboxylation reactions which led to the formation of various short chained carboxylic acids, surface saturation with acidic functional groups as determined by the surface acidity measurements and proven by the increase in the intensity of FT-IR peaks associated with carboxyl and phenolic C-O groups. Furthermore, hydrogen peroxide treatment resulted in preferential removal of volatile organic carbons and led to the purification of biochar as evident by the new, more intense and sharper peaks in the region of 1600-1000 cm-1. These FT-IR peaks are considered as the more recalcitrant fraction of biochar and were shown to be mostly associated with transformation products of lignin and cellulose formed during pyrolysis. The incubation trial confirmed that biochar cannot be utilized as a sole carbon source without the addition of nutrients or glucose, to activate microbial activity within the columns. Furthermore, abiotic oxidation can be facilitated by oxidative soil minerals such as birnessite, but oxidation with atmospheric oxygen did not result in the evolution of CO2 from biochar. The average CO2 production in pot trials without plants in both the fertilized and unfertilized treatments increased linearly (R2= 0.80; 0.79 respectively) with increasing biochar application rates when biochar was the main carbon sources. Anaerobic degradation of biochar by a methanogenic consortium was much more efficient in utilizing biochar as a carbon source, compared to aerobic digestion. The anaerobic digesters maintained a chemical oxygen demand (COD) removal efficiency of 30% per week with continuous production of CO2, whilst methane production was very erratic. We proposed that better control over pH and alkalinity as well as an increase in hydraulic retention time would improve both the COD removal efficiency and methane production. Field incubations resulted in various degrees of oxidation at different incubation sites. An increase in the oxygen content and a decreased in the carbon content of biochar‘s elemental composition and also an increase in the surface acidity due to a larger amount of carboxyl acid groups on the surface as seen in the increase in the FT-IR peak at 1700 cm-1 confirmed that biochar are susceptible to oxidation under field conditions. We came to the conclusion that oxidation and mineralization of biochar in this trial occurred at a faster rate in soils with a higher microbial activity. The pot trials, confirmed that biochar does not serve as a fertilizer even though it did increase total biomass production between biochar application rates of 0.05-2.5 % (w/w). For agricultural purposes the addition of biochar should always be applied together with NPK fertilizer. In both the wheat and green bean trials it was confirmed that biochar application rates of 0.05-0.5% (w/w) on the sandy, slightly acidic soil used in this trial resulted in the greatest biomass production and fertilizer use efficiency. Biochar additions resulted in considerable increases in soil pH and C/N ratios which were considered as the main reasons for the decrease in microbial biomass in the unfertilized green bean treatments as it made the uptake of N more limited. The addition of fertilizer however, alleviated N-supply constraints and as a result promoted microbial growth at all biochar application rates of pot trial 1. However, biochar did not promote mycorrhyzal colonization and caused a decrease in the mycorrhizal colonization of roots with increasing biochar application rates and within biochar layers. Biological nitrogen fixation, however, reacted positively to the addition of biochar. High biochar application rates significantly enhanced the plants reliance on these symbiotic relationships. We hypothesized that biochar physically immobilized N into its microvoids through capillary suction and then served as a physical barrier between plant roots and absorbed N. However, immobilzation of N by microbes could also have contributed to the decrease in N uptake if one takes into account that microbial activity was higher (respiration data) at the higher biochar application rates. Further investigations are needed to warrant this hypothesizes. AFRIKAANSE OPSOMMING: Biochar (houtskool) is deur talle wetenskaplikes die lof toegeswaai as ‘n doeltreffende manier om koolstofdioksied uit die atmosfeer te verwyder en in ‘n baie stabiele vorm in die grond vir honderde tot duisende jare te stoor, terwyl dit die grondvrugbaarheid en produktiwiteit bevorder. As daar in ag geneem word dat geen beduidende hoeveelheid houtskool in die omgewing opgaar nie ondanks groot hoeveelhede wat wêreldwyd deur natuurlike en mensgemaakte brande gevorm word, is die doel van hierdie studie om die afbraak en die interaksie van biochar met plante en grondmikrobes beter te verstaan. Om hierdie doel te bereik is die volgende eksperimente uitgevoer: Beheerde chemiese oksidasie is op die biochar toegepas deur gebruik te maak van verskillende konsentrasies waterstofperoksied in 'n poging om die ensiematiese afbraak van biochar deur basidiomysete na te maak. Die veranderinge wat plaasvind in die struktuur en chemie van biochar is daarna bestudeer. Daarbenewens is die aerobiese and anearobiese afbraak van biochar toegepas beide in vitro- en in vivo-, om die veranderinge wat in biochar se elementele samestelling en chemie plaasvind gedurende oksidasie en ook die faktore wat 'n bepalende rol in die tempo waarteen biochar afbreek, te ondersoek. Die invloed van biochar in die grond op vrylewende en simbiotiese mikrobiese populasies, sowel as die impak daarvan op die totale plant biomassa produksie en ontwikkeling van plantwortels, is vasgestel tydens drie groeitonnel potproewe waarby koring en boontjies as planttoetsspesies gebruik is Dit is bewys dat biochar byna volledig deur H2O2 afgebreek kan word, meestal deur hidroksilasie en karboksilasie reaksies wat gelei het tot die vorming van 'n verskeidenheid kort ketting karboksielsure, 'n biochar oppervlak versadig met suurvormende funksionele groepe soos bepaal en bewys deur die toename in intensiteit van die FT-IR (Fourier Transvorm Infrarooi Spektroskopie) pieke geassosieer met karboksiel en fenoliese C-O groepe. Die behandeling van biochar met H2O2 het by voorkeur die vlugtige organise koolstof verwyder wat gelei het tot suiwering van die biochar, wat bevestig is deur die nuwe, meer intens en skerper FT-IR pieke in die area tussen 1600-1000 cm-1. Die FT-IR pieke word beskou as die meer weerstandbiedende fraksie van biochar en daar is bewys dat die pieke meestal met getransformeerde produkte van lignien en sellulose wat tydens pirolise gevorm is, geassosieer word. Die inkubasie proef het bevestig dat biochar nie deur mikrobes benut kan word as enigste bron van koolstof sonder die byvoeging van nutriente of glukose nie, om die mikrobes binne die inkubasie kolom te aktiveer. Daarbenewens kan abiotiese oksidasie van biochar deur oksidatiewe grondminerale soos birnessite (δ-MnO2) gefasiliteer word, terwyl oksidasie van biochar deur atmosferiese suurstof nie tot enige CO2 produksie gelei het nie. Nogtans het die gemiddelde CO2 produksie in die boontjie potproef, sonder die plante, in beide die onbemeste en bemeste behandelings linieer toegeneem (R2= 0.80; 0.79 onderskeidelik) met toenemende aanwendingskoers van biochar, toe biochar die dominante bron van koolstof was. Anaerobiese afbraak van biochar deur 'n metanogeniese konsortium was heelwat meer effektief in die benutting van biochar as enigste koolstofbron in vergelyking met aerobiese afbraak. Die anaerobiese verteertoestel het konstant 30% van die chemiese suurstof behoefte (CSB) weekliks verwyder, gepaardegaande met die voortdurende produksie van CO2, terwyl metaangasproduksie baie onegalig was. Dit word voorgestel dat met beter beheer oor pH en alkaliniteit en ook 'n langer hidrouliese retensie tyd, kan beide die CSB verwyderingseffektiwiteit en metaangasproduksie verbeter kan word. Veld inkubasies het verskeie mates van oksidasie meegebring tussen die verskillende inkubasie liggings. 'n Toename in die suurstofinhoud en 'n afname in die koolstof inhoud van biochar se elementele samestelling sowel as 'n toename in die oppervlak suurheid weens die groter hoeveelheid karboksielsure aan die oppervlak soos blyk uit die FT-IR piek by 1700 cm-1, het bevestig dat biochar wel vatbaar is vir oksidasie onder veld kondisies. Die gevolgtrekking was dat biochar oksidasie en mineralisasie in hierdie proef teen 'n vinniger tempo plaasgevind het in die gronde met hoer mikrobiese aktiwiteit. Die potproewe het bevestig dat biochar nie as bemestingsstof sal dien nie, alhoewel dit tot 'n toename in die biomassa produksie gelei het tussen die biochar aanwendingskoerse van 0.05-2.5% (w/w). Vir landbou doeleindes moet die aanwending van biochar altyd gepaardgaan met NPK bemesting. Beide die koring- en boontjie proewe het bevestig dat die biochar aanwendingskoerse tussen 0.05-0.5% (w/w) op die sanderig, effens suur grond wat gebruik is in die proef, gelei het tot die hoogste biomassa produksie en bemestingseffektiwiteit. Die toediening van biochar het gelei tot merkbare toenames in grond pH en C/N verhoudings en hierdie toestande was beskou as die hoof redes vir die afname in mikrobiese biomassa in die onbemeste boontjie behandelings omdat dit die opname van N meer beperk. Die toediening van bemesting het egter die beperkings op N voorsiening opgehef en as gevolg hiervan die mikrobiese biomassa bevorder by alle biochar aanwendingskoerse. Biochar het egter nie mikorrisa kolonisasie bevorder nie en het gelei tot =n afname in die mikorrisa kolonisasie van die wortels met toenemende biochar aanwendingskoerse en binne in die biochar lae van potproef 1. Biologiese stikstof vaslegging het egter positief reageer op die toediening van biochar. Hoë biochar aanwendingskoerse het beduidend die plant se afhanklikheid op hierdie simbiotiese verhouding verhoog. Ons hipotese is dat die biochar fisies N immobiliseer binne in die mikro-ruimtes deur kapillêre suigaksie en dan as 'n fisiese versperring dien tussen die plantwortels en die geabsorbeerde N. Die immobilisasie van minerale N deur mikrobes kon egter ook grootliks bygedra het tot die afname in N opname as daar in ag geneem word dat mikrobiese aktiwiteit (respirasie data) hoër was by die hoër biochar aanwendingskoerse. Verdere ondersoeke moet daarom uitgevoer word om hierdie hipotese te bevestig.

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Duncan, Corrine. "Seeds, soils and moisture : ecophysiology to inform mine site restoration in arid zones." Thesis, Federation University Australia, 2019. http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/180639.

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Mining in arid regions of Australia is followed by restoration and rehabilitation efforts. However, attempts to reintroduce many woody plant species have been unsuccessful. Water is the key limiting resource to plant growth and seed germination in arid zones. In this thesis, I investigated ecophysiological processes that may help improve recruitment across novel arid landscapes. I tested seed traits and dormancy cues of eight keystone plants and found that six of them had non-dormant, rapidly germinating seeds; a trait we propose is an adaptation to the region’s unpredictable rainfall. To identify the germination niche of species, I incubated seeds under different temperatures and water potentials, and found drought avoidance to be an important survival strategy for arid species. I collected soil samples to compare biophysicochemical properties of reconstructed soils to remnant ecosystems, and found that the distribution of clay content in the reconstructed soils did not mirror the remnant soils, compromising their ability to sustain perennial vegetation. I also monitored soil moisture and found that soil reconstruction reduces rainfall infiltration and retention, and subsequently increases evaporation. The synthesis of these results demonstrate some of the limitations to successful restoration in these systems, such as (1) unknown dormancy cues and poor seed longevity, (2) infrequent and episodic plant recruitment due to water limitation, and (3) reduced hydrological function of reconstructed soils. The failure to reinstate hydrological function is the major constraint to ecological restoration in this arid zone. Nonetheless, results from this study suggest that restoration is possible through more strategic use of seed, careful selection of drought tolerant species, and increasing soil moisture. Further failures to reinstate ecosystem function and community dynamics in arid zones with reconstructed soils can be prevented by understanding the edaphic constraints to plant establishment, and ameliorating conditions to mimic ecohydrological processes in remnant ecosystems. Doctor of Philosophy

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Diaz, de Arends Miriam Leonarda. "Ecophysiology and phenology of very dry tropical forest trees : effects of soil characteristics, rainfall and irrigation." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624548.

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Vassallo, Joanne. "The bioavailability and biological effects of nanomaterials towards Escherichia coli : with reference to the soil environment." Thesis, University of Plymouth, 2018. http://hdl.handle.net/10026.1/11611.

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Engineered nanomaterials (ENMs) are specifically designed with different functionalities to satisfy required industrial, medical or commercial purposes. The inevitable release of these materials to the environment may impact negatively bacteria that are essential for the ecosystem’s well-being. This work aimed to identify features that determine the hazardous nature of nanomaterials to bacteria. At first, the bacterial growth inhibition concentrations for silver (Ag), cupric oxide (CuO), cadmium telluride quantum dots (CdTe QDs), titanium dioxide (TiO2), nanodiamonds and multi-walled carbon nanotubes were determined on Escherichia coli K-12 MG1655 grown in 96-well plates. The nano-forms of Ag, CuO, TiO2 and the CdTe QDs were found to display more growth inhibitory effects than their bulk equivalents. The metal salts of silver and copper were still more toxic than their equivalent ENM forms; on the contrary the CdTe QDs were found to be more toxic than their metal salts equivalent. The surface coatings of the ENMs were not found to be significant contributors of bacterial growth inhibition. This screening assay could be adapted as a first tier approach; providing an early input into the hazard assessment of nanomaterials to bacteria. The upscale determination of bacterial growth inhibition tests in 250 ml Erlenmeyer flasks manifested similar results to those observed in 96-well plates. The growth inhibition tests with E. coli were also conducted in an anaerobic fermentative environment. The presence of the ENMs was not found to disrupt the functionality of the fermentation respiratory pathway of the bacterium. However, the results indicated a more severe bacterial growth inhibition response to the presence of silver, copper and the cadmium/tellurium based ENMs as compared to the aerobic growth exposures. Finally, from the adaptation of a human ingestion simulation of soil containing CuO NPs, no greater concerns of metal bioaccessibility were identified from the potential ingestion of the nano-forms of CuO versus the metal salt.

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Thakali, Sagar. "Terrestrial biotic ligand model (TBLM) for copper, and nickel toxicities to plants, invertebrates, and microbes in soils." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 2.00 Mb., 340 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3221133.

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Eriksson, Mikael. "The Role of Soil Biology and Plant Health – Brandywine Tomatoes Grown with Different Microbial Additions." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-290296.

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The microbial life in the soil is essential for providing a functioning habitat for plants to grow. A literature study was conducted to investigate the knowledge and science behind soil biology. The purpose of this study was to define what is soil health and how it is influenced by the soil microbial communities. The literature study concluded that the ability of soil biology to benefit plants includes a variety of aspects. Nutrient availability, soil structure and pest resistance are all greatly influenced by soil microbes. To practically examine these theories, an experiment was conducted where Brandywine tomatoes where grown in three different scenarios. A commercial potting soil, Hasselfors ekojord, was used as substrate in all groups. In the control group (C) the plants were grown only in the substrate. In the second group (R), the seeds where treated with a microbial inoculum and then planted in the substrate. In the third group (RE), the same treatment as in R was done to the seeds and here, compost extract were also added to the RE group. The plants were grown in separate pots in a greenhouse and the growth rate was observed and documented as well as the total harvest. In the end of the growing season a chemical and biological analysis was done to the soil as well as a sap analysis on the leaves. The plant growth where similar among the groups although R and RE showed slightly higher growth rates in the later stages of the growing season. The harvested fruit was highest in C but not significantly. The microbial contents were high in all soils though more fungi communities in the RE and bacterial communities in C. The chemical analysis showed high nitrate concentrations in the leaves in C. In R and especially RE the nitrate conversion into amino acids and proteins where higher wish indicates that these groups are more resilient to pests like aphids. Det mikrobiella livet i jorden är avgörande för att skapa en fungerande livsmiljö för växter. En litteraturstudie genomfördes för att undersöka nuvarande kunskap och vetenskap bakom markbiologi. Syftet med denna studie var att definiera markhälsa och hur den påverkas av det mikrobiella livet i jorden. Slutsatsen från denna litteraturstudie var att jordbiologins förmåga att gynna växter innefattar en rad olika aspekter. Näringstillgänglighet, markstruktur och skadedjursbeständighet påverkas starkt av jordmikrober. För att praktiskt granska dessa teorier genomfördes ett experiment där Brandywine-tomater odlades i tre olika scenarier. En kommersiell plantjord, Hasselfors ekojord, användes som huvudsubstrat i alla grupper. I kontrollgruppen (C) odlades växterna endast i substratet. I den andra gruppen (R) behandlades frön med en mikrobiell ympning innan de såddes i substratet.I den tredje gruppen (RE) utfördes samma fröbehandling som i R och kompostextrakt tillsattes också till RE-gruppen. Växterna odlades i separata krukor i ett växthus och tillväxthastigheten observerades och dokumenterades liksom den totala skörden. I slutet av växtsäsongen gjordes en kemisk och biologisk analys av jorden samt en savanalys på bladen. Tillväxten var likartad bland grupperna även om R och RE visade något högre tillväxttakt i de senare stadierna av växtsäsongen. Skördad frukt per planta var högst i C, dock intesignifikant. Den mikrobiella koncentrationen var hög i alla jordar men mer svamporienterat i RE och bakterieorienterat i C. Den kemiska analysen visade högt nitratinnehåll i bladen i C. I R och särskilt i RE var nitratomvandlingen till aminosyror och proteiner högre vilket indikerar att dessa grupper är mer motståndskraftiga mot skadedjur så som bladlöss.

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Godow, Bratt Tora, Mathilda Stigenberg, Andreas Elenborg, Sarah Ågren, and Andreas Medhage. "To monitor the microbial biodiversity in soil within Uppsala." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-444210.

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This is an exploration of the potential for a citizen science project, with the goal to get the general public involved in microbial soil biodiversity around Uppsala, Sweden. Biodiversity serves an important role in how an ecosystem performs and functions. A large part of Earth's biodiversity exists below ground in soil, where microorganisms interact with plants. It would be beneficial to analyse the abundance and spread of some microorganisms in order to gain a better understanding of soil biodiversity. We suggest that one species family to study could be Phytophthora. Phytophthora is a genus of oomycetes that often are pathogenic, causing disease in various trees and other plants. It is unknown exactly how widespread the genus is today, making it extra interesting for the proposed study. For the general public to be able to do this a device needs to be developed that is easy to use and preferably could be used directly in the field. An isothermal amplification method is suitable for identifying the microorganism under these conditions. Many isothermal amplification methods are expensive, perhaps too expensive for a citizen science study, but have great potential for easy field testing. We propose a device utilizing RPA and lateral flow strips. RPA - Recombinase Polymerase Amplification is a method for amplification that might be suitable since it is simple, sensitive, and has a short run time. It is however expensive, which is an issue, but isothermal amplifications are expensive across the board. Lateral flow strips can be used to visualize the results. They utilize antibodies to detect the previously amplified amplicons, and give a positive or negative test answer that would be understandable to even untrained study participants. One of the biggest obstacles identified in this project concerns amplifying DNA from a soil sample, because an extraction step is necessary. The methods we have identified for extraction are not performable in the field, since they require centrifugation. In the proposition for a device a possible work-around for this is proposed, but since it has yet to be tested it is not yet known whether it will work or not.

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Eck, Jenalle L. "Variation in Tropical Tree Seedling Survival, Growth, and Colonization by Arbuscular Mycorrhizal Fungi near Conspecific Adults: Field and Shadehouse Experiments in Panama." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503242529467534.

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28

Ramahlo, Masetle Nelson. "Physico-chemical and biological characterization of soils from selected farmlands around three mining sites in Phalaborwa, Limpopo Province." Thesis, University of Limpopo (Turfloop Campus), 2013. http://hdl.handle.net/10386/1127.

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Thesis (M.Sc. (Soil Science)) --University of Limpopo, 2013 The study was conducted to assess the impact of mining activities on selected soil physical, chemical and microbial properties on farmlands around three selected mining sites. Nine soil samples were collected from each of the following farms : Hans Merensky, Mogoboya and Leon Tom, Foskor Mine and JCI mining sites, respectively. Additional nine soil samples were collected from non-polluted Waterbok farm that serves as a control for the purpose of comparison. The samples were taken at 0–15, 15–30, 30–45 cm depths at three sampling points on each farm for physical, chemical and biological studies. However, soil samples collected for microbial (fungi, bacteria and actinomycetes) counts were surface (0–15 cm) soil samples. Soil chemical properties determined include pHw, electrical conductivity (ECe), exchangeable acidity (EA), organic carbon, available phosphorous, exchangeable cations as well as heavy metal (i.e. Mn, Zn, Cu, Pb, Cd, As and Sb) concentrations. The physical parameters determined include texture (sand, silt and clay) as well as bulk density. Soil pHw and ECe values decreased with depth; and ranged from 6.94 to 6.50 and from 12.24 to 10.76 mS cm-1, respectively. Exchangeable acidity showed a gradual increase with depth and ranged from 0.72 to 0.80 cmol(+)(kg), while percent organic carbon decreased with depth ranging from 1.41 to 2.19 %. Exchangeable cations, particularly K and Mg increased with depth while Ca decreased marginally with soil depth. Available phosphorous content decreased following increases in distance from the pollution source while heavy met.al contamination decreased with soil depth but increased further away from the pollution source. Significantly high loads of Pb, As and Sb were recorded at all depths on the three farms around the mining sites, which were largely responsible for the pollution but worse on the Leon Tom farm; with Pb constituting the greatest pollutant. The concentration of extractable heavy metals in the studied areas was in the order: As >Sb>Pb>Zn>Cu >Mn >Cd. Cadmium level appeared generally very low in all samples while elevated levels of Mn, Cu and Zn were detected at all depths in the polluted soils.Significant differences in microbial levels were detected at the various sampling points. The highest count of 3.82 and 6.20 CFU g-1 for fungi and actinomycete, respectively were both from the Leon Tom farm, while 6.46 CFU g-1 counts for bacteria was obtained from Mogoboya farm. Interestingly, fungal and actinomycetes activities were more sensitive to heavy metal contamination than bacteria that were significantly increased following soil pollution. National Research Foundation (NRF)

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Roth, McKenzie L. "Analysis of Bacterial Abundance and Species Diversity in Various Soils." Ashland University Honors Theses / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=auhonors1355166102.

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30

Goldstein, Arthur. "Conception d'une méthode de diagnostic fonctionnel des microbiotes du sol en agriculture grâce à la millifluidique de gouttes." Thesis, Université Paris sciences et lettres, 2021. http://www.theses.fr/2021UPSLS038.

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Les microbes des sols sont utiles à l’agriculture : ils aident les plantes à acquérir des nutriments, dégradent les déchets, protègent les plantations contre les pathogènes… Comprendre les interactions entre les microorganismes, les plantes et les autres éléments du sol pourrait permettre de gagner en productivité tout en préservant l’environnement. Dans cet optique, un des enjeux en agronomie est d’être capable de caractériser les communautés microbiennes des sols de manière fonctionnelle ; c’est-à-dire de quantifier les services qu’elles peuvent rendre à l’agriculture et à la société de manière générale. Par exemple, un « bon » microbiote d’un point de vue fonctionnel protégera les plantes des maladies et les aidera à acquérir des nutriments, il dégradera les éventuels polluants néfastes et limitera les efflux de gaz à effet de serre. Pour mener cette caractérisation, l’identification et l’analyse génétique des microbiotes ne suffisent pas ; des outils technologiques manquent.Nous avons choisi de nous occuper de ce problème en exploitant une technologie qui n’avait pas été employée jusqu’ici en agriculture : la millifluidique de gouttes, qui consiste à manipuler des gouttes de quelques centaines de nanolitres, séparées les unes des autres par une phase huileuse. En l’occurrence, nous avons utilisé l’automate de culture microbiologique en gouttes de la startup MilliDrop. Nous avons étudié une fonction : la capacité à solubiliser le phosphate du sol, un nutriment essentiel aux plantes. Nous avons adapté la recette d’un milieu de culture utilisé depuis plus de 70 ans : le milieu Pikovskaya. Il contient des particules de phosphate de calcium et nous avons dû mener un travail de formulation physico-chimique important pour transférer ces particules en gouttes et les y maintenir dispersées. Nous avons par ailleurs ajouté au milieu deux sondes fluorescentes qui nous ont permis de suivre à la fois le pH de nos gouttes et l’activité respiratoire. Ce protocole expérimental prêt, nous l’avons appliqué à une douzaine de sols agricoles.Grâce à la fluorescence de la résazurine, notre sonde d’activité respiratoire, nous avons estimé la concentration en cellules cultivables dans nos échantillons. Nous avons montré que l’on obtenait en tendance le même nombre de microorganismes avec notre méthode en gouttes qu’avec la méthode classique de dénombrement de colonies sur boîtes de Petri.En exploitant un bloc optique conçu pour notre projet, nous avons pu mener des mesures de néphélométrie (scattering) en gouttes et évaluer la capacité de nos microorganismes à faire baisser ce signal, ce que nous interprétons au moins partiellement comme la capacité des microorganismes à solubiliser le phosphate. Grâce à notre sonde pH, nous avons pu montrer que la baisse du signal de scattering était associée à une chute du pH sous 5,8 (qui correspond au pH théorique en-dessous duquel les particules se dissolvent par seul effet de l’acidité) dans environ 90% des gouttes. Il est possible que parmi les 10% des gouttes restantes, on trouve des microorganismes qui sécrètent de grandes quantités de chélatants, ce qui représente un intérêt agricole particulier. On trouve systématiquement plus de microorganismes solubilisateurs en gouttes qu’avec la méthode traditionnelle sur boîte de Petri, sans pour autant avoir de corrélation entre ces deux modes de mesure. Si différentes hypothèses pourraient être testées pour éclaircir ce phénomène, nos résultats remettent en question le test traditionnel sur boîtes.Notre protocole est rapide et simple : nos expériences ont pu être réalisées par une technicienne non spécialisée, le traitement de données est automatisable et une demi-heure de travail suffit à analyser quatre sols (plus avec de prochaines versions de la machine). Les résultats en gouttes sont obtenus sept fois plus vite que ceux sur boîtes de Petri. Cela fait de notre protocole un candidat pour devenir un test fonctionnel utilisé à grande échelle Soil microbes are useful in agriculture: they help plants to acquire nutrients, degrade waste, protect crops against pathogens, etc. Understanding the interactions between microorganisms, plants and other soil elements could help increase productivity while preserving the environment. From this perspective, one of the challenges in agronomy is to be able to characterize soil microbial communities in a functional manner; that is, to quantify the services they can render to agriculture and society in general. For example, a "good" microbiota from a functional point of view will protect plants from diseases and help them acquire nutrients, degrade harmful pollutants and limit the influx of greenhouse gases. To carry out this characterization, the identification and genetic analysis of microbiotes is not sufficient; technological tools are lacking.We chose to address this problem by exploiting a technology that has not been used in agriculture until now: droplets millifluidics, which consists in manipulating drops of a few hundred nanoliters, separated from each other by an oily phase. In this case, we used the automated microbiological drop culture system from MilliDrop, a startup from our lab. We studied one function: the ability to solubilize soil phosphate, an essential plant nutrient. We adapted the recipe of a culture medium used for more than 70 years: Pikovskaya medium. It contains particles of calcium phosphate and we had to carry out an important physicochemical formulation work to transfer these particles into drops and keep them dispersed. We also added two fluorescent probes to the medium that allowed us to monitor both the pH of our drops and the respiratory activity. Once the experimental protocol was ready, we applied it to a dozen agricultural soils.Thanks to the fluorescence of resazurin, our respiratory activity probe, we estimated the concentration of cultivable cells in our samples. We showed that the same number of microorganisms was obtained in trend with our drop method as with the classical method of counting colonies on Petri dishes.By using an optical block designed for our project, we have been able to conduct optical scattering measurements in drops and evaluate the ability of our microorganisms to lower this signal, which we interpret at least partially as the ability of the microorganisms to solubilize phosphate. Thanks to our pH probe, we were able to show that the fall of the scattering signal was associated with a pH fall below 5.8 (which corresponds to the theoretical pH below which particles dissolve by the sole effect of acidity) in about 90% of the drops. It is possible that among the remaining 10% of the drops there are microorganisms that secrete large quantities of chelating agents, which is of particular agricultural interest. There are systematically more solubilizing microorganisms in the drops than with the traditional Petri dish method, but there is no correlation between these two methods of measurement. While different hypotheses could be tested to clarify this phenomenon, our results call into question the traditional test on plates.Our protocol is quick and simple: our experiments were carried out by a non-specialized technician; data processing can be automated, and half an hour of work is enough to analyze four soils (more with future versions of the machine). The results in drops are obtained seven times faster than those on Petri dishes. This makes our protocol a candidate to become a functional test used on a large scale

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Muddimer, Stephen. "Phosphorus (P) partitioning among co-occurring plants : competition for P acquisition across different forms of P and through soil microbes." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/16000/.

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Nieminen, T. (Timo). "Detection of harmful microbes and their metabolites with novel methods in the agri-food production chain." Doctoral thesis, University of Oulu, 2009. http://urn.fi/urn:isbn:9789514290039.

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Abstract This thesis aimed at developing methods for tracking the environmental origins of microbial contaminants of the food chain. We worked on three targets: i) environmental mycobacteria ii) toxinogenic Bacillus species iii) post-harvest fungi in strawberry jam. Our aim was to develop methods for early detection of the above contaminants, which have the potential to endanger consumer health. We developed a novel method based on 16S rRNA hybridization for tracking the reservoirs of potentially pathogenic environmental mycobacteria in piggeries and soil. From 1010 to 1012 16S rRNA molecules of environmental mycobacteria were found per gram of peat, wood shavings and straw in piggeries with a high prevalence of infections. These beddings may thus be a source of mycobacteria for pigs. We found 1010–1011 of mycobacterial 16S rRNA molecules per gram of Finnish forest soil, indicating that the soil contained 107–109 mycobacteria per gram. These numbers exceed the previous cultivation-based estimates of mycobacterial content in Finnish soils. To elucidate the role of mastitis in the input of toxinogenic Bacillus into the dairy production chain, milks were sampled from mastitic cows. Twenty-three Bacillus isolates were screened for toxins using the sperm cell motility inhibition assay. Four of the six toxinogenic isolates found were identified as Bacillus pumilus and two as Bacillus licheniformis. The isolates produced toxic substances that were heat-stable (100 °C) and soluble in methanol, thus being of non-protein nature. The extracts prepared from the toxin-producing isolates disrupted the plasma membrane of exposed sperm cells at concentrations 1–15 μg ml-1 (B. pumilus) 20–30 μg ml-1 (B. licheniformis). The toxic action of the mastitis-associated B. licheniformis strains was similar to that of the lipopeptide lichenysin A. The genes for lichenysin synthetase were found in these strains by PCR. This study revealed that heat-stable toxin-producing strains of B. pumilus and B. licheniformis occur in milk of mastitic milking cows. They may enter the dairy production chain when milk of clinically healthy cows recovered from mastitis is sent to dairies. Many foodborne contaminant fungi are known to produce volatile organic compounds. We investigated the suitability of such metabolites as early indicators of fungal contamination of strawberry jam. We found that volatile organic compounds commonly produced by the contaminant fungi in strawberry jam were 2-pentanone, styrene, 3-methyl-1-butanol, 1,3-pentadiene and ethanol. The results indicate that these compounds could be used to detect fungal contamination of jam.

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Slabbert, Etienne. "Microbial communities of riparian ecotone invaded by non-indigenous Acacias." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20367.

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Jenkins, Sommer. "Ecophysiological principles governing the zonation of puccinellia (Puccinellia ciliata) and tall wheatgrass (Thinopyrum ponticum) on saline waterlogged land in south-western Australia." University of Western Australia. School of Earth and Geographical Sciences, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0133.

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Puccinellia (puccinellia ciliata) and tall wheatgrass (Thinopyrum ponticum) often show ecological zonation in saline landscapes, with puccinellia occurring in less elevated more saline/waterlogged locations, and tall wheatgrass occurring in more elevated less saline/waterlogged locations. The aims of this study were to: (a) characterize the observed ecological zonation at a field site, (b) quantify the effects of variables likely to explain growth differences of the two plants in glasshouse experiments, and (c) identify and compare anatomical and physiological mechanisms that explain these zonation patterns. At an experiment in the field near Kojonup (0522824E, 6244579N), puccinellia was found to colonise the lower more severely salinised and waterlogged zones of the landscape, with tall wheatgrass occupying the higher less affected zones. These differences in zonation were clearly associated with variance in soil salinity and water-table depth. Glasshouse experiments in soil revealed that low pH values, low calcium concentrations and variation in salinity alone did not explain the ecological zonation observed in the field. However, there was a substantial difference in the responses of the two plant species to waterlogging in combination with salinity. Puccinellia grew better under saline waterlogged conditions than tall wheatgrass, which was associated with better regulation of Na+ and K+ under saline/waterlogged conditions than in tall wheatgrass. Under non-saline conditions, waterlogging (hypoxia) decreased shoot weights in puccinellia by 15% and in tall wheatgrass by 20%. Similar growth results were obtained in nutrient solution culture, where waterlogging was simulated by lowering the oxygen in solutions through bubbling with N2 gas. Under saline hypoxic conditions, puccinellia, compared to tall wheatgrass, showed increased growth and maintenance of selectivity of K+ over Na+ across adventitious roots. Solution experiments revealed adaptive traits responsible for conveying better growth and ion maintenance present in puccinellia, but not tall wheatgrass, such as inducement of a barrier to radial oxygen loss in the basal regions of adventitious roots (not previously reported in the literature for puccinellia), formation of root aerenchyma and packing of cortical cells and suberin deposition in hypodermal and endodermal root cell layers. These results should assist in targeting pasture species, and predicting their growth response, in saline and waterlogged landscapes. Further work on examining the genetic material of puccinellia is warranted in order to identify genes that could be transferred into crop plants to convey salt and waterlogging tolerance.

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Servais, Shelby M. "Changes in Soil Microbial Functioning in Coastal Wetlands Exposed to Environmental Stressors and Subsidies." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3821.

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Environmental perturbations are ubiquitous features of ecosystems and shape ecological structure and function. Climate change will alter the intensity and frequency of disturbances and expose ecosystems to novel combinations of useful inputs (subsidies) and harmful inputs (stressors). Coastal wetlands are particularly vulnerable to changing environmental conditions and are increasingly exposed to effects of interacting subsidies and stressors. In particular, the Florida Coastal Everglades, which has experienced accelerated change due to a history of water management practices, is vulnerable to new disturbances associated with climate change. The low-lying Florida Everglades faces multiple disturbances from storm surge, nutrient enrichment, and sea-level rise which will influence its responses to future environmental perturbations. Microbial communities are often used to characterize environmental change because of their high surface area to volume ratio, permeable membrane, and quick turnover rates. Therefore, assessing how microbial function changes can provide insights into how subsidies and stressors interact to alter biogeochemical cycles. I tested how nutrient enrichment can alter ecosystem responses to stress and found that it did not promote recovery in mangrove plants. I examined how long-term exposure to salinity and phosphorus (the limiting nutrient in the Everglades) affected microbial enzyme activity and found that salinity alone acts as a suppressor of enzyme activity but phosphorus addition can mitigate salinity stress in sawgrass soil. I tested how pulses of salinity can affect the microbially-mediated breakdown of organic material and found that the microbial community was functionally redundant and unaffected by saltwater pulses; however, microbial activity was consistently lower in the brackish marsh compared to the freshwater marsh. I investigated how gradients of salinity and phosphorus affected freshwater and brackish soils and determined previous exposure to saltwater intrusion dominates affects microbial function and soil composition. Across these experiments, I found that environmental perturbations alter the microbial-mediated processing of nutrients and carbon, and legacies of previous disturbances influence the microbial response to new disturbance regimes.

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Showalter, Julia M. "Evaluation of Topsoil Substitutes for Restoration of Appalachian Hardwoods on Strip Mined Land." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/34638.

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Current surface mine reclamation in Appalachia involves returning the land to approximate original contour by grading the surface and planting grasses and early-successional trees. This results in a greatly altered ecosystem compared to the native forest that was there prior to mining. The reclaimed land is usually degraded economically and environmentally because mine soils are usually less productive than the native soils, and because the mined sites do not provide the same level of ecosystem services. This research addressed constraints to the return of the native ecosystem by assessing how mine spoil properties and treatments affect native tree species and soil microorganisms. A 4x2x3 factorial greenhouse experiment was used to examine the growth of one-year-old Fraxinus americana, Quercus rubra, and Liriodendron tulipifera as well as herbaceous plant occurrence and microbial biomass and activity. Three mine spoils, brown, weathered sandstone (BWS), white, unweathered sandstone (WUS), and gray, unweathered shale (GUH) were compared with undisturbed forest topsoil (UFT) to determine their suitability for tree growth. Half of each of the four media was inoculated with a 2.5-cm layer of topsoil. BWS was the optimal spoil material for the growth of F. americana, Q. rubra and microbial populations. Foliar nutrient analysis indicated that L. tulipifera was highly dependent on nutrient levels and was unable to grow well on any of the spoil types due to deficiencies. Inoculation with topsoil increased tree growth on the GUH spoil, and increased microbial activity and presence of herbaceous plants across all growth media. The field study was used to determine what spoil properties most influenced three-year-old Quercus alba growth. This information was used to test a mine quality classification model. Northeast facing sites with sandy spoils high in nutrients, moderate in pH, and high in microbial populations were optimal for tree growth. These variables explained 52% of the variation in tree growth. Tree growth was also highly correlated with tree foliar nutrient levels, further suggesting that tree growth was influenced by spoil nutrients. Microbial biomass and dehydrogenase production were also regressed against soil properties and were dependant on a moderate pH, high nitrogen levels, and low salt content. These variables explained 53% of the variability in microbial biomass and 50% of the variability in enzyme production. These studies suggest that tree growth and soil microbial populations are closely linked, and both are affected by mine spoil properties. During mined land reclamation, mine spoils conducive to tree growth should be selected if return of the native ecosystem is the reclamation goal. Master of Science

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Susser, Jessica R. "Can we reduce phosphorus runoff into Lake Erie by stimulating soil biota?" University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1515756009087471.

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Sunwar, Sharmila. "Multi-Element Composition of Triglochin Maritima L. from Contrasting Habitats including Hot Springs and Metal Enriched Areas." Diss., North Dakota State University, 2011. https://hdl.handle.net/10365/29177.

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The aim of this PhD research was to study multi-element composition in wetland plants from contrasting habitats, including hot springs, temporary wetlands, and metal-rich areas. Triglochin maritima L. (seaside arrowgrass) was chosen for the study because this species is common in alkaline/saline soils and is adapted to diverse habitats. Eleocharis rostellata, Juncus balticus, Salix exigua, S. boothii, and S. wolfii were also included in the study. Field studies and greenhouse experiments were conducted to study the multi-element composition in plants. In the greenhouse experiment the effects of temperature and soil biota on multielement uptake in T. maritima were studied. Root-zone soils and plant samples were analyzed for 32 - 50 elements using inductively coupled plasma OES/MS spectrometry. The expected outcomes from this research were: 1) the development of multi-element fingerprints for T. maritima and other plant species from contrasting habitats, and 2) a better understanding of the effects of temperature and soil biota on multi-element uptake in T. maritima. Habitat specific element concentration patterns in T. maritima were observed; concentrations of Mn, Li, and B were high in plants from hot spring influenced wetlands, whereas Ca, P, Mg, Fe, Sr, Ba, Ti, and Cu were higher in the plants of temporary wetlands. J. balticus and Salix species from mine impacted and uncontaminated sites revealed distinct differences in multi-element fingerprints. J. balticus showed high concentrations of S, K, Mn, Fe, Cu, Al, As, and Cd at contaminated sites compared to un-contaminated sites. Multi-element fingerprints of Salix species showed that S. boothii had higher concentrations of Mn, Fe, Al, and Ti compared to S. exigua and S. wolfii. To our knowledge for the first time the association of mycorrhizal fungus in T. maritima was confirmed, and significant effects of temperature on element concentrations, contents, and their translocation in plants were observed. Generally, the distribution of the total contents of P, Na, Mn, B, Cu, Mo, Li, Sr, Ti, and Cs in both roots and leaves were lower at 40 ?C compared to 20 and 30 ?C, but their distribution and translocation from root to leaves were higher at 40?C. Even though the biological and physiological functions of Li, Sr, Ba, Rb, and Ti in plants are not fully understood, these elements were substantially taken up by T. maritima, and significant positive correlations of these elements were found with elements that have known biological functions. Overall, concentrations of Ca, P, Mg, Mn, B, Sr, and Ba in T. maritima showed variation due to differences in habitats, temperature, and experimental growing conditions (greenhouse and field condition). Concentration patterns of Na, K, and Zn were species specific and affected by temperature. Li concentrations varied due to habitat differences, growth conditions, and species differences. Future research directions could include: 1) identification of the fungal species associated with T. maritima and studies to elucidate their possible role in survival of T. maritima in the elevated temperature of hot springs, 2) the effects of soil factors, such as salinity and 3) seasonal variation in uptake and translocation, particularly for the less studied elements with yet unrecognized but potential biological functions in plants. NIH Grant Number P20 RR016471 from the INBRE Program of the National Center for Research Resources North Dakota State University. Department of Biological Sciences Robert H. Levis II Cross Ranch Fellowship North Dakota State University. Environmental and Conservation Sciences program

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Bailey, Jennifer Diane. "Vertical Distribution of Wetland Plant Roots and Their Associated Bacteria in Groundwater-fed Wetlands." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1452708738.

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Szota, Christopher. "Root morphology, photosynthesis, water relations and development of jarrah (Eucalyptus marginata) in response to soil constraints at restores bauxite mines in south-western Australia." University of Western Australia. School of Plant Biology, 2009. http://theses.library.uwa.edu.au/adt-WU2010.0058.

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Bauxite mining is a major activity in the jarrah (Eucalyptus marginata Donn ex Sm.) forest of south-western Australia. After mining, poor tree growth can occur in some areas. This thesis aimed to determine whether soil constraints, including reduced depth and compaction, were responsible for poor tree growth at low-quality restored bauxite mines. In particular, this study determined the response of jarrah root morphology, leaf-scale physiology and growth/development to soil constraints at two contrasting (low-quality and high-quality) restored bauxite-mine sites. Jarrah root excavations at a low-quality restored site revealed that deep-ripping equipment failed to penetrate the cemented lateritic subsoil, causing coarse roots to be restricted to the top 0.5 m of the soil profile, resulting in fewer and smaller jarrah trees. An adjacent area within the same mine pit (high-quality site) had a kaolinitic clay subsoil, which coarse roots were able to penetrate to the average ripping depth of 1.5 m. Impenetrable subsoil prevented development of taproots at the low-quality site, with trees instead producing multiple lateral and sinker roots. Trees in riplines, made by deep-ripping, at the high-quality site accessed the subsoil via a major taproot, while those on crests developed large lateral and sinker roots. Bauxite mining is a major activity in the jarrah (Eucalyptus marginata Donn ex Sm.) forest of south-western Australia. After mining, poor tree growth can occur in some areas. This thesis aimed to determine whether soil constraints, including reduced depth and compaction, were responsible for poor tree growth at low-quality restored bauxite mines. In particular, this study determined the response of jarrah root morphology, leaf-scale physiology and growth/development to soil constraints at two contrasting (low-quality and high-quality) restored bauxite-mine sites. Jarrah root excavations at a low-quality restored site revealed that deep-ripping equipment failed to penetrate the cemented lateritic subsoil, causing coarse roots to be restricted to the top 0.5 m of the soil profile, resulting in fewer and smaller jarrah trees. An adjacent area within the same mine pit (high-quality site) had a kaolinitic clay subsoil, which coarse roots were able to penetrate to the average ripping depth of 1.5 m. Impenetrable subsoil prevented development of taproots at the low-quality site, with trees instead producing multiple lateral and sinker roots. Trees in riplines, made by deep-ripping, at the high-quality site accessed the subsoil via a major taproot, while those on crests developed large lateral and sinker roots.

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41

Yadav, Heena [Verfasser], Bettina [Gutachter] Hause, Edgar [Gutachter] Peiter, and Franziska [Gutachter] Krajinski-Barth. "Interactions of Medicago truncatula with soil-borne microbes : role of MtTPS10 in defense against the root pathogen Aphanomyces euteiches / Heena Yadav ; Gutachter: Bettina Hause, Edgar Peiter, Franziska Krajinski-Barth." Halle (Saale) : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2019. http://d-nb.info/1210728192/34.

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Zethof, Jeroen H. T. [Verfasser], Karsten [Gutachter] Kalbitz, Karsten [Akademischer Betreuer] Kalbitz, Georg [Gutachter] Guggenberger, and M. Estela [Gutachter] Nadal-Romero. "The role of extracellular polymeric substances from microbes in soil aggregate stabilization in semiarid grasslands / Jeroen H.T. Zethof ; Gutachter: Karsten Kalbitz, Georg Guggenberger, M. Estela Nadal-Romero ; Betreuer: Karsten Kalbitz." Dresden : Technische Universität Dresden, 2021. http://d-nb.info/1237320054/34.

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43

Huang, Jianjun. "Ecological responses of two forest understory herbs to changes in resources caused by prescribed fire alone on in combination with restoration thinning." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1195062013.

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44

Abdou, Mohamed Adam Mohamed [Verfasser]. "Root-knot nematodes: abundance in organic farming, differentiation among populations, microbes attached to juveniles in soil, and bacterial antagonists / Mohamed Adam Mohamed Abdou. Julius Kühn-Institut. Technische Universität Carolo-Wilhelmina zu Braunschweig." Quedlinburg : Julius Kühn-Institut, 2014. http://d-nb.info/1105491455/34.

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45

Adam, Mohamed [Verfasser]. "Root-knot nematodes: abundance in organic farming, differentiation among populations, microbes attached to juveniles in soil, and bacterial antagonists / Mohamed Adam Mohamed Abdou. Julius Kühn-Institut. Technische Universität Carolo-Wilhelmina zu Braunschweig." Quedlinburg : Julius Kühn-Institut, 2014. http://nbn-resolving.de/urn:nbn:de:101:1-201607056010.

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46

Grellmann, Doris. "Top-down and bottom-up effects in a Fennoscandian tundra community." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-96883.

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The objective of this thesis was to investigate the effects of mammalian grazers, such as microtine rodents and reindeer, (top-down effects) and nutrient availability (bottom- up effects) on the plant community of a tundra heath. I conducted a large-scale fertilization experiment and studied the impact of grazers using exclosures. I measured the effects of fertilization and grazing on soil microbial activity and nutrient cycling. I investigated the responses to fertilization of the invertebrate community, I studied the effects on the quality of bilberry as food for mammalian herbivores, and I looked at how concentrations of nutrients and carbon-based secondary defences against herbivory fluctuated between seasons in unfertilized and fertilized treatments. The results of my thesis show that the plant community investigated is exposed to a strong top-down control by mammalian herbivores. On the fertilized and grazed areas the aboveground biomass of the vascular plant community did not increase compared to unfertilized areas. However, the productivity of the plant community was clearly nutrient- limited. During the eight years of the experiment, on the fertilized areas plant biomass was significantly increased inside the herbivore exclosures In my study mammalian herbivores at comparatively low densities and grazing outside the growing season were sufficient to control the biomass of a heterogeneous plant community. Microtine rodents (Norwegian lemmings and grey-sided voles) preferred the fertilized areas for overwintering. The food plant quality of bilberry for grey-sided voles was improved on the fertilized areas throughout the year. Grazing decreased the nitrogen storage in the aboveground plant biomass. Reindeer and rodents had also important indirect effects on the plant community by decelerating soil nutrient cycling and soil microbial activity. This effect may be accelerated by the impact of herbivore on plant species composition. Graminoids, which contained the highest nitrogen concentrations in their tissues, increased rapidly on the fertilized areas, but their abundance was significantly lower on grazed fertilized areas. The invertebrate community was detritus-based and received their energy indirectly from the litter via soil microbes and detritivores. Fertilization increased the biomass of invertebrate carnivores, but had no effect on the biomass of invertebrate herbivores. Apparent competition between detritivores and invertebrate herbivores, mediated by carnivorous invertebrates predating on both of them, is supposed to keep the densities and grazing pressure of invertebrate herbivores low. Grazing damage by invertebrates was very low and only 0.021 % of the total vascular plant biomass was removed. Diss. (sammanfattning) Umeå : Umeå universitet, 2001, härtill 6 uppsstser. digitalisering@umu

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Rodrigues, Gleice Gomes. "Fixação e alocação de carbono em plantações clonais de eucalipto sob diferentes densidades de plantio." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/11/11150/tde-05102017-104939/.

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Decisões tomadas no planejamento da implantação florestal, como a densidade do plantio e o material genético, alteram a disponibilidade de recursos naturais tais como nutrientes, água e luz e consequentemente afetam a assimilação do carbono, que está diretamente relacionada ao crescimento da planta. Ainda são escassas as informações de como e quanto a densidade de plantio e o material genético afetam a fixação de carbono pelas ávores. O objetivo desse trabalho foi avaliar os padrões de fixação e alocação de carbono em plantações clonais de Eucalyptus sp. em duas densidades de plantio (3x2 m e 3x4 m), em um Latossolo Vermelho Distrófico T ípico A moderado. O estudo foi desenvolvido na Estação Experimental de Ciências Florestais de Itatinga-SP - ESALQ/USP, com três materiais clonais de Eucalyptus urophylla: AEC 0144, AEC 224 e COP 1404. O delineamento experimental utilizado foi em blocos casualizados, com esquema fatorial 3 x 2, sendo composto por três clones de eucalipto em dois espaçamentos, com 6 repetições para cada tratamento. Durante o intervalo de um ano (dos 40 aos 52 meses de idade) foram determinados a Produtividade Primária Líquida da Parte Aérea (ANPP: incremento da biomassa aérea somada ao folhedo), a Respiração Autotrófica da Parte Aérea (Rp: respiração das folhas e do tronco com base com base na ANPP, assumindo um valor constante de eficiência de uso do carbono (CUE) de 0,53 (GIARDINA et al., 2003)), o Fluxo de Carbono Abaixo do Solo (TBCF: produção e respiração das raízes grossas e finas, exsudatos das raízes e produção de substratos usados por micorrizas) e a Produtividade Primária Bruta (GPP: somatório dos fluxos de carbono) para os seis tratamentos avaliados. A maior produtividade encontrada para o clone AEC 0144 no espaçamento 3x2 m foi resultado de uma maior GPP (5997,45 g C m-2 ano-1), maior partição de carbono para incremento de tronco (30%) e menor partição da GPP para TBCF (34%). A ANPP variou de 1453,99 g C m-2 ano-1 (Clone COP 1404 no espaçamento 3x2 m) a 2288,78 g C m-2 ano-1 (Clone AEC 0144 no espaçamento 3x2 m), sendo os maiores fluxos encontrados para os clones AEC 0144 em ambos espaçamentos e para o clone COP 1404 no espaçamento 3x4 m. A variação encontrada nos valores de respiração da parte aérea seguiram o mesmo padrão dos resultados da ANPP. O TBCF foi significadamente superior para os clones AEC 0144 e AEC 224 no espaçamento 3x2 m com 2056,36 g C m-2 ano-1 e 1903,83 g C m-2 ano-1, respectivamente; e para o clone COP 1404 no espaçamento 3x4 m (1927,43 g C m-2 ano-1). Houve correlação positiva do TBCF com a GPP, mas não com a ANPP. Decisions not planned for forest deployment, such as planting density and genetic material, alter the availability of natural resources such as nutrients, water and light and consequently affect the assimilation of carbon, which is directed to plant growth. They are still scarce as information on how and how much planting density and genetic material for a fixation of carbon by trees. The objective of this work was to evaluate the carbon allocation patterns in clonal plantations of Eucalyptus sp. in two planting densities (3x2 m and 3x4 m), in a typical Typic A moderate Dystrophic Red Latosol. The study was developed at the Experimental Station of Forest Sciences of Itatinga-SP - ESALQ / USP, with three clonal materials of Eucalyptus urophylla: AEC 0144, AEC 224 and COP 1404. The experimental design was a randomized complete block design with a factorial scheme 3 x 2, being composed of three clones of eucalyptus in two spacings, with 6 replicates for each treatment. During the one-year interval (from 40 to 52 months of age) was determined Aboveground Net Primary Productivity (ANPP: increase of the aerial biomass added to the litterfall), Aboveground Autotrophic Respiration (Rp: leaf respiration and (CUE) of 0.53 (GIARDINA et al., 2003)), Total Belowground Carbon Flux (TBCF: production and respiration of the roots) and Gross Primary Productivity (GPP: sum of the carbon fluxes) for the six treatments evaluated. The higher productivity found for the clone AEC 0144 in the 3x2 m spacing resulted from a higher GPP (5997.45 g C m-2 year-1), larger carbon partition for trunk increment (30%) and smaller partition from GPP for TBCF (34%). The ANPP ranged from 1453.99 g C m-2 year-1 (Clone COP 1404 in spacing 3x2 m) to 2288.78 g C m-2 year-1 (Clone AEC 0144 in 3x2 m spacing) Found for clones AEC 0144 in both spacings and COP 1404 in 3x4 m spacing. The variation found in aboveground autotrophic respiration values followed the same pattern of ANPP results. The TBCF was significantly higher for clones AEC 0144 and AEC 224 at 3x2 m spacing with 2056.36 m-2 year-1 and 1903.83 m-2 year-1, respectively; and for clone COP 1404 in 3x4 m spacing (1927.43 m-2 year-1). There was a positive correlation between TBCF and GPP, but not with ANPP.

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Bleby, Timothy Michael. "Water use, ecophysiology and hydraulic architecture of Eucalyptus marginata (jarrah) growing on mine rehabilitation sites in the jarrah forest of south-western Australia." University of Western Australia. School of Plant Biology, 2003. http://theses.library.uwa.edu.au/adt-WU2004.0004.

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[Truncated abstract. Please see the pdf format for the complete text. Also, formulae and special characters can only be approximated here. Please see the pdf version for an accurate reproduction.] This thesis examines the water use, ecophysiology and hydraulic architecture of Eucalyptus marginata (jarrah) growing on bauxite mine rehabilitation sites in the jarrah forest of south-western Australia. The principal objective was to characterise the key environment and plant-based influences on tree water use, and to better understand the dynamics of water use over a range of spatial and temporal scales in this drought-prone ecosystem. A novel sap flow measurement system (based on the use of the heat pulse method) was developed so that a large number of trees could be monitored concurrently in the field. A validation experiment using potted jarrah saplings showed that rates of sap flow (transpiration) obtained using this system agreed with those obtained gravimetrically. Notably, diurnal patterns of transpiration were measured accurately and with precision using the newly developed heat ratio method. Field studies showed that water stress and water use by jarrah saplings on rehabilitation sites were strongly seasonal: being greatest in summer when it was warm and dry, and least in winter when it was cool and wet. At different times, water use was influenced by soil water availability, vapour pressure deficit (VPD) and plant hydraulic conductance. In some areas, there was evidence of a rapid decline in transpiration in response to dry soil conditions. At the end of summer, most saplings on rehabilitation sites were not water stressed, whereas water status in the forest was poor for small saplings but improved with increasing size. It has been recognised that mature jarrah trees avoid drought by having deep root systems, however, it appears that saplings on rehabilitation sites may have not yet developed functional deep roots, and as such, they may be heavily reliant on moisture stored in surface soil horizons. Simple predictive models of tree water use revealed that stand water use was 74 % of annual rainfall at a high density (leaf area index, LAI = 3.1), high rainfall (1200 mm yr-1) site, and 12 % of rainfall at a low density (LAI = 0.4), low rainfall (600 mm yr-1) site, and that water use increased with stand growth. A controlled field experiment confirmed that: (1) sapling transpiration was restricted as root-zone water availability declined, irrespective of VPD; (2) transpiration was correlated with VPD when water was abundant; and (3) transpiration was limited by soil-to-leaf hydraulic conductance when water was abundant and VPD was high (> 2 kPa). Specifically, transpiration was regulated by stomatal conductance. Large stomatal apertures could sustain high transpiration rates, but stomata were sensitive to hydraulic perturbations caused by soil water deficits and/or high evaporative demand. No other physiological mechanisms conferred immediate resistance to drought. Empirical observations were agreeably linked with a current theory suggesting that stomata regulate transpiration and plant water potential in order to prevent hydraulic dysfunction following a reduction in soil-to-leaf hydraulic conductance. Moreover, it was clear that plant hydraulic capacity determined the pattern and extent of stomatal regulation. Differences in hydraulic capacity across a gradient in water availability were a reflection of differences in root-to-leaf hydraulic conductance, and were possibly related to differences in xylem structure. Saplings on rehabilitation sites had greater hydraulic conductance (by 50 %) and greater leaf-specific rates of transpiration at the high rainfall site (1.5 kg m-2 day1) than at the low rainfall site (0.8 kg m-2 day1) under near optimal conditions. Also, rehabilitation-grown saplings had significantly greater leaf area, leaf area to sapwood area ratios and hydraulic conductance (by 30-50 %) compared to forest-grown saplings, a strong indication that soils in rehabilitation sites contained more water than soils in the forest. Results suggested that: (1) the hydraulic structure and function of saplings growing under the same climatic conditions was determined by soil water availability; (2) drought reduced stomatal conductance and transpiration by reducing whole-tree hydraulic conductance; and (3) saplings growing on open rehabilitation sites utilised more abundant water, light and nutrients than saplings growing in the forest understorey. These findings support a paradigm that trees evolve hydraulic equipment and physiological characteristics suited to the most efficient use of water from a particular spatial and temporal niche in the soil environment.

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Booi, Nozuko. "Structure and function of heuweltjies across a rainfall gradient in the South-Western Cape." Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6467.

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Thesis (MScConEcol (Conservation Ecology and Entomology))--University of Stellenbosch, 2011. ENGLISH ABSTRACT: Heuweltjies are below ground termitaria found along the west coast and the south-western and -eastern Cape. They traversing different climates, soil and vegetation types within the Succulent Karoo and Fynbos biomes. From a birds eye view, heuweltjies appear as near-circular landscape features, demonstrating clear difference in vegetation structure to their surroundings. A study of aspects of the structure and function of heuweltjies, mima-like mounds of south-western South Africa was undertaken. The main aim of the study was to investigate topsoil properties and processes and vegetation structure and the ecophysiology of plants growing on these mounds, and compare it to areas off these patches. Four study sites across a rainfall gradient were chosen for soil and vegetation studies (two within the Succulent Karoo and two at the Fynbos biome). Ten sampling sites on heuweltjies and 10 off heuweltjie (interpatch) were chosen at each study site for these analyses. Soils samples from the top 10 cm were analysed for total nitrogen (N) and carbon (C) content, phosphorus (P) concentrations, particle-size distributions, pH and electrical conductivity (related to salinity). Soil biogeochemistry studies (i.e. potential N mineralization, potential soil respiration and phosphatase activity) were also done in the laboratory. In the field, the cover of soil cryptogams, selected plant growth forms and selected physical variables at each site, on and off heuweltjies, were estimated on 1m2 grids. Two of the study sites, one in the Succulent Karoo and one in Fynbos, were chosen for field measurements of stomatal conductance, predawn and midday xylem water potentials of two growth forms (deciduous and evergreen non-succulent shrubs) at selected times in the duration of the study. Leaf samples were taken to make once-off measurements of specific leaf area, C and N isotope compositions (δ13C, δ15N), and foliar N content. Furthermore, a fertilization experiment that has been running at the Tierberg Karoo Research Centre (Succulent Karoo) since 1997, where 10g m-2 of N have been added to interpatch vegetation twice annually, was included in the stomatal conductance and xylem water potential studies. The aim of including the fertilization experiment was to ascertain whether interpatch vegetation will eventually resemble heuweltjie vegetation in ecophysiology following N fertilization. Soil water probes were inserted, 10 cm deep, on one on heuweltjie and one off heuweltjie site for the long-term estimation of gravimetric water content and temperature at the Tierberg Karoo Research Centre. Heuweltjie soils were found to be hotspots for nutrients and biogeochemical activity. They had elevated levels of total % C, % N and available P (mg kg-1) compared to surrounding interpatch soils. pH and electrical conductivity (μS cm-1) of these soils were also high compared to interpatch areas. Heuweltjie soils have higher silt content and retain more water, and for a longer period following a rainstorm. Potential soil respiration, potential N mineralization and alkaline and acid phosphatase activity were generally higher on heuweltjies.Cover of the selected plant growth forms differed little between heuweltjies and the surrounding vegetation but site differences were observed. Heuweltjies differed from interpatches in the cover of soil cryptogams, with higher cover of mosses and lower cover of lichens on mounds. There was higher cover of plant litter and termite frass on the heuweltjies.There was a decrease in soil available P and increase in non-succulent shrub cover from low to high rainfall areas. On the other hand no significant differences were found in the xylem water potential of interpatch and heuweltjie plants at either of the study sites. At the Tierberg Karoo Research, stomatal conductance of interpatch plants was higher and water use efficiency (δ13C) lower compared to that of heuweltjie plants suggesting some level of water stress for heuweltjie plants at this site. Here, heuweltjie plants also had higher foliar N, lower C/N ratio values, signs of high photosynthetic potential and highly decomposable litter and higher δ15N. At Jonaskop, stomatal conductance and water use efficiency did not differ between heuweltjies and interpatch plants. There were also no differences in foliar N concentrations, C/N ratios and δ15N between heuweltjie and interpatch plants at this site. Plants growing in high N plots (the fertilizer plots) had higher xylem water potential and more variable stomatal conductance than those growing in control plots. The results of this study have shown heuweltjies to be hotspots for nutrients and biogeochemical cycling, and given enough water, will be ideal patches for plant growth. In the Succulent Karoo, high salinity (and finer textured soils) on the heuweltjies may contribute to water stress during dry periods, and together with disturbance, provide bottom-up controls on plant physiology, and ultimately, vegetation structure. In the Fynbos, plants may be limited by nutrients on heuweltjies, possibly because of increased interspecific competition, while increased rainfall may also lead to more nutrients leaching from the topsoils. The results presented are especially relevant to restoration programs, and may shed some light on restoration trajectories after overgrazing, cultivation and mining activities. AFRIKAANSE OPSOMMING: Heuweltjies is ondergrondse termitaria wat langs die weskus, die suid-wes en oos Kaap van Suid Afrika voorkom. Hulle kom voor onder verskillende klimaatstreke, grondtipes en planttipes wat binne die Sukkulente Karoo en Fynbos biome voorkom. Vanuit die lug uitgesien, verskyn heuweltjies as sirkelvormige landskapseienskappe, wat duidelike verskille in plant struktuur en die omringende omgewing demonstreer. ŉ Studie van aspekte van struktuur enfunksie van ŉ heuweltjies, mima-agtige hope vansuidwestelike Suid-Afrikais onderneem. Die hoofdoel van die studie was om die eienskappe van oppervlakgrondeen -prosesse, plant struktuur, en die ekofisiologie van plante wat op heuweltjies groei te ondersoek, en dit te vergelyk met areas af van hierdie kolle. Vier studieareas wat oor „n reënvalgradient strek is gekies vir grond en plantegroei studies (twee binne die Sukkulente Karoo en twee binne die Fynbos biome). Tien monsterareas op heuweltjies en 10 af van heuweltjies (omringende areas) is gekies binne elke studiearea vir die bogenoemde analises. Grondmonsters van die boonste 10 cm van die grond is geneem en geanalieseer vir totale stikstof (N) en koolstof (C), fosfor (P) konsentrasies, gronddeeltjiegrootte, pH, en elektriese geleidingsvermoë, (hou verband met soutgehalte). Grond biogeochemie studies (d.i. potensiële stikstof mineralisasie, potensiële grond respirasie en fosfatase aktiwiteit) is ook in die laboratorium uitgevoer. In die veld was die dekking van grond kriptogame, geselekteerde plant groeivorms en fisiese veranderlikes by elke lokaliteit, beide op en van heuweltjies op 1m2vierkante bereken. Twee studie lokaliteite, een in die Sukkulent Karoo en een in die Fynbos, is gekies vir veld metings van huidmondjiegeleiding, voor dagbreek en middag xileem potensiale van twee groei vorms (bladwisselende en immergroen nie-sukkulente struike) op geselekteerde tye gedurende die studie. Blaarmonsters is geneem om eenmalige metings te maak van die spesifieke blaararea, C en N isotoop komposisies (δ13C, δ15N), en blaar N inhoud. Verder is „nbemestingseksperiment wat by die Tierberg Karoo Navorsing Sentrum (Sukkulente Karoo) loop sedert 1997, waar 10gm-2 van N jaarliks twee keer bygevoeg word by die plante wat tussen heuweltjies groei ingesluit in die stomata geleiding en xileem water potensiaal studies. Die doel van die bevrugting eksperiment was om vas te stel of die omliggende plante (af van heuweltjies) uiteindelik soos die van die heuweltjiessal lyk in terme van ekofisologie nadat dit met stikstof bemes is. Grondwater monitoreringsapparaat was ingesit (10cm diep) op een op heuweltjie en een lokaliteitaf van die heuweltjie vir die langtermyn bepaling van gravimetriese water inhoud (m3m-3) en temperatuur by die Tierberg Karoo Navorsing Sentrum. Daar is gevind dat grond op heuweltjies “skerpkolle” is vir voedingstowwe en biogeochemiese aktiwiteit. Hulle het ook verhoogte vlakke van totale %C, % N, en beskikbare P (mg kg-1) teenoor die omliggende areas om die heuweltjies. pH en elektriese geleidingsvermoë (μS cm-1) van hierdie gronde was ook hoër in vergelyking met die omliggende areas. Heuweltjie grond het „n hoër sout inhoud gehad en behou meer water vir ŉ langer periode na ŉ reënstorm. Potensiële grond respirasie, potensiële stikstof mineralisasie, en alkaliese en suur fosfatase aktiwiteit is oor die algemeen hoër op heuweltjies. Die voorkoms van die geselekteerde plant groeivorms verskil min tussen heuweltjies en die omliggende omgewing, maar verskille tussen studie areas is opgemerk. Heuweltjies het verskil van areas af van heuweltjies in die voorkoms van grond kriptogame, met ŉ hoër voorkoms van mosse en ŉ laer voorkoms van ligene op die heuweltjies. Daar was hoër voorkoms van plantafvalmateriaal en termiet uitwerpsel op die heuweltjies. Daar was ŉ afname in grond P (mg kg-1) en ŉ toename in nie-sukkulente struik bedekking van lae tot hoë reënval areas. Daar was geen verskil in die xileem water potensiaal van plante op die heuweltjies of af van die heuweltjies by enige van die studie lokaliteite nie. By die Tierberg Karoo Navorsing Sentrum was huidmondjie geleiding van plant in die areas tussen heuweltjies hoër en die water gebruik doeltreffendheid (δ13C) laer in vergelyking met die van die heuweltjie plante, wat op„n sekere vlak waterstres dui in heuweltjie plante by hierdie studiearea. Hier het heuweltjie plante ook hoër blaar N, laer C/N waardes, tekens van hoër fotosintetiese potensiaal en hoogs afbreekbare afvalmaterialgehad asook hoër δ15N. By Jonaskop het huidmondjie geleiding en water gebruik doeltreffendheid nie verskil tussen heuweltjie en omliggende plante nie. Daar was ook geen verskille in blaar N konsentrasies, C/N verhoudings en δ15N tussen heuweltjie en omliggende plante by hierdiestudiearea nie. Plante wat groei in hoë stikstof plotte, het hoër xileem water potensiaal (minder stres) en meer veranderlike stomatal geleiding as die plante wat in die kontrole plotte groei. Die resultate van die studie het getoon dat heuweltjies “skerpkolle” is van voedingstowwe en biogeochemiese siklusse, en gegewe genoeg grondwater, sal ideale areas wees vir die groei van plante. In die Sukkulente Karoodra hoë soutgehalte (en fyner grond teksture) op die heuweltjies by tot water stres gedurende droë tye, en saam met versteurings dra dit by tot grond tot plant kontrole op plantfisiologie, en uiteindelik plant gemeenskapsstruktuur. In die Fynbos word plante op die heuweltjies beperk deur te min voedingstowwe, moontlik omdat daar ŉ toename is in intraspesifieke kompetisie, terwyl hoër reenvalkan lei tot hoër loging van voedingstowwe vanuit die bogrond. Die resultate wat hier gerapporteer word is veral relevant vir restourasieprogramme, en mag lig werp op restourasie trajekte na oorbeweiding, aanplanting van gewasse en mynbou-aktiwiteite.

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Grigg, Alasdair M. "An ecophysiological approach to determine problems associated with mine-site rehabilitation : a case study in the Great Sandy Desert, north-western Australia." University of Western Australia. School of Plant Biology, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0118.

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[Truncated abstract] Establishment of vegetation and ecosystem functioning is central to the mitigation of environmental impacts associated with mining operations. This study investigated the ecophysiological functioning of mature plants in natural vegetation and applied this knowledge to diagnose problems affecting plant health and causes of poor plant cover at a mine-rehabilitation site. Ecophysiological parameters, including plant water relations and mineral nutrition, were studied in conjunction with soil physical, hydraulic and chemical properties. The natural ecosystem at the study location in the Great Sandy Desert is characterised by sand dunes and interdunes with distinct plant communities on each. One of the most notable features of the vegetation is the presence of large Corymbia chippendalei trees high on the dunes and relatively small scattered shrubs in the interdunes. Triodia grasses (spinifex), dominate the vegetation in both habitats but different species occur in each; T. schinzii is restricted entirely to the dunes, and T. basedowii occurs only in the interdunes. It was hypothesised that the deep sandy dunes afford greater water availability but lower nutrient supply to plants in this habitat compared with those occurring in the lower landscape position of the interdunes. Water-relations parameters (leaf water potentials, stomatal conductance, d13C) revealed that dune plants, particularly woody species, displayed higher water status and water use than closely related and often congeneric plants in the interdunes. Nutrient concentrations in soils were significantly higher in the interdunes, but concentrations in foliage were similar for related species between habitats. It is concluded that the dunes provide a greater store of accessible water than the soil profile in the interdunes. ... Following an experimental wetting pulse equivalent to a summer cyclone event, A. ancistrocarpa plants displayed significant increases in stomatal conductance, leaf water potential and sap velocity in lateral roots within three days of irrigation at the natural site and two days at the rehabilitation site. Secondary sinker roots originating from distal sections of lateral roots were evidently supplying water to maintain hydraulic function in laterals, thus enabling a fast pulse response. This was accentuated at the rehabilitation site where roots were confined closer to the surface. These results indicate that plants at the rehabilitation site are more dependent on small pulses of water and have less access to deep reserves than plants at the natural site. It is concluded that high runoff losses and insufficient soil depth are major factors contributing to plant water stress, and combined with the direct impacts of erosion, are largely responsible for plant death and ultimately poor plant cover. These issues can be alleviated if cover soil depth is increased to more than 0.5 m and slope angles are reduced to <12o. This study demonstrates the value of an ecophysiological approach for diagnosing problems affecting plant establishment at mine-rehabilitation sites. Furthermore, it has provided recommendations that will improve the rehabilitation strategy and lead to the development of a well vegetated, resilient ecosystem on a stable and non-polluting land form.

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Dissertations / Theses on the topic 'Ecophysiology of soil microbes'

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