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1
Kappala, Saritha. "Seedling establishment on Oryza sativa L." Thesis, University of Liverpool, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540049.
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Jernigan, Marcus B., Mitchel P. McClaran, Sharon H. Biedenbender, and Jeffrey S. Fehmi. "Uprooted buffelgrass thatch reduces buffelgrass seedling establishment." TAYLOR & FRANCIS INC, 2016. http://hdl.handle.net/10150/616972.
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Buffelgrass (Pennisetum ciliare (L.) Link), a non-native perennial bunchgrass, invades ecologically intact areas of the Sonoran Desert. It competitively excludes native plants and increases fire frequency and intensity. Since the 1990s, whole buffelgrass plants have been manually uprooted and removed to control the invasion in southern Arizona. Uprooting plants results in bare, disturbed soil which promotes buffelgrass seed germination. This study examined whether leaving entire uprooted buffelgrass plants (thatch) on a field site reduces future buffelgrass establishment compared to removing uprooted plants from the site. A secondary goal was to determine whether light reduction and autoallelopathy were major factors in the negative effect of thatch on buffelgrass seedling density. Field plots with an average of 8,095 kg/ha thatch had 1.9 buffelgrass seedlings/m(2) which was significantly fewer than the 2.9 seedlings/m(2) in plots without thatch. Thatched portions of thatch plots (50% of their total area) had only 0.7 seedlings/m(2). In the greenhouse, which reduced outdoor light intensity by 35.2%, buffelgrass seeds sown in bare soil resulted in significantly higher seedling density than beneath buffelgrass thatch. Potential autoallelopathic chemicals leached from partially decomposed buffelgrass thatch and leached thatch had an intermediate but not significant (p = 0.09) effect on seedling numbers. Results suggest that leaving uprooted buffelgrass plants has the benefit of reducing seedling establishment in the area disturbed by uprooting.
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McKimmie, Tim, and Albert Dobrenz. "Salt Tolerance During Seedling Establishment in Alfalfa." College of Agriculture, University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/203790.
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Deposition of salts from irrigation water is an increasing concern for Arizona farmers and agronomists. Selection for salt tolerance during the seedling stage has been undertaken over the past three years. Yield tests were conducted in greenhouses and a significant increase in dry matter production was shown in the selected material.
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Ganade, Gislene Da Silva. "Seedling establishment in Amazon rain forest and old-fields." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339196.
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Baumer, Marilyn Cabrini. "Tree Seedling Establishment Under the Native Shrub, Asimina Triloba." Wright State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=wright1183587955.
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Botha, Susan. "The influence of rainfall variability on savanna tree seedling establishment." Master's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/6238.
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Includes bibliographical references (leaves 111-114).<br>My thesis investigates the rainfall requirements necessary for tree seedling survival of different savanna species in the first year of growth. Results from a field drought experiment showed that dry season survival for seedlings of Acacia nigrescens and Philenaptera vialacea was not related to wet season length. Instead mortality was highest immediately after germination despite irrigation to minimize dry spells. Furthermore there was no relationship between seedling size and the length of the dry spell seedlings of Acacia nigrescens and Philenaptera vialacea grown in basalt clay in the greenhouse, could survive. This was in contrast to seedlings of Scleracarya birrea and Terminalia sericea grown in granite sand, where number of dry days survived increased with number of growth days received. There was no significant differences in rainfall variability (t-test: tL III = 1.56, P = 0.121, F-ratio = 1.13) between a semi-arid (Satara) and semi-mesic (Pretoriuskop) site within the Kruger National Park despite significant differences in rainfall totals (t-test: tl, III = 4.40, P < 0.000, F-ratio 3.41). Results from a soil-water model show that seedling recruitment can occur at least twice a decade in the Satara area, which should be frequent enough to allow a transition to a woodland state over time. These results suggest that a mechanism other than the effect of rainfall variability on seedling establishment is required to explain the co-existence of trees and grasses at Satara. The lack of field germination, the absence of a seed bank and the germination of added seed at the field experiment site after rainfall emphasizes seed limitation as an important bottleneck at Satara. Higher herbivore biomass at Satara compared to Pretoriuskop may limit seedling establishment opportunities by destroying seed and seedlings of tree species.
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Lindén, Elin. "The development of established shrub seedlings in persistent historical reindeer milking grounds." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-98888.
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This study focuses on how established shrub seedlings (Salix myrsinifolia x phycilifolia and Vaccinium vitis-idaea) develop in historical milking grounds. Historical milking grounds are cultural remains from the intensive reindeer herding era when the Sami migrated with closely controlled herds. Although the places were never fenced, the high concentration of reindeer close to the tenting grounds created patches of grass and forb dominated vegetation in areas outherwise dominated by deciduous or ericoid shrubs. Despite about 100 years of abandonment the shrubs have not come back and the milking grounds are still clearly visible in the landscape. One theory why the former milking grounds are so stable is that shrubs cannot establish from seedlings due to unfavorable abiotic conditions, or due to competitive dominance of already established forbs and grasses. I tested this hypothesis by planting shrub seedlings in the milking grounds and in reference areas, with and without neighboring vegetation and investigated seedling survival and growth. The results show that shrub seedlings are able to both survive and develop in milking grounds suggesting that the seedling state is not the limiting factor in shrub encroachment in the milking grounds.
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Carroll, Charlotte Elizabeth Ella. "The importance of aquaporins in Arabidopsis thaliana germination and seedling establishment." Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/66471/.
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Aquaporins are membrane channels transporting water and small molecules across the membranes of various intracellular compartments. Plant aquaporins constitute the Major Intrinsic Protein (MIP) family, consisting of 35 members in Arabidopsis thaliana, all exhibiting expression patterns which are specific in tissue type and developmental timing. Aquaporins are thought to be vital to plant growth, development, and response to drought. However, little work has been done to clarify the exact roles of particular isoforms in each of these aspects. The MIP isoforms TIP3;1 and TIP3;2 are uniquely localised to both the plasma membrane and tonoplast. In addition, they are the only aquaporins present in the maturing and germinating Arabidopsis seeds. Their potential importance in these developmental processes has therefore been speculated, but is yet to be fully elucidated. In addition, it is suspected that a C-terminal domain unique to TIP3 isoforms is responsible for their plasma membrane localisation. However little has been done to dissect the cellular sorting route they take, or the order in which they reach both membranes. By misexpressing MIP isoforms, including TIP3, in transgenic Arabidopsis and systematically assessing the resulting effect on germination and seedling growth in water limiting conditions, it was found that increased expression of Arabidopsis thaliana aquaporin isoforms at atypical developmental time points can confer drought tolerance in both germination and seedling growth. More specifically, increasing the number of aquaporins at the plasma membrane can enhance tolerance to drought during germination, implying a fundamental role for the dual localisation of TIP3 at this developmental stage. Fluorescent protein fusions to TIP3 were employed to dissect the order of this isoform’s trafficking, and pharmacological techniques confirmed the route. From this, an inducible expression system for TIP3 has been established to study dual sorting, and TIP3 were confirmed to traffic independently of the Golgi complex in embryonic tissues, regardless of the presence or absence of their C-terminal motif.
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Ruhland, Beverlee M. "Morphological aspects of seedling establishment in four temperate region Phorandendron spp." PDXScholar, 1986. https://pdxscholar.library.pdx.edu/open_access_etds/3702.
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Four species of Phoradendron were examined for seedling morphology: P. bolleanum subsp. densum (on Juniperus), P. californicum (on Prosopis), P. juniperinum subsp. juniperinum (on Juniperus, P. villosum subsp. villosum (on Quercus). The main species used in the study was P. juniperinum, using the other species for comparison. The initial shoot(s) of P. juniperinum may develop from the epicotyl of the developing seedling, from adventitious buds which arise from a cushion of tissue, termed the haustorial cushion, formed beneath the holdfast, or from both positions. When shoots arise only from adventitious buds the original seedling remains attached in a lateral position, often persisting for a number of years, giving the false impression of an autoparasite establishing itself near the base of the plant. In P. bolleanum and P. villosum, initial shoots arise from the epicotyl although adventitious shoots may also develop, particularly in P. bolleanum. In contrast, P. californicum shoots are entirely adventitious in origin, and the initial seedling can frequently be seen near the center of the cluster of adventitious shoots. Cotyledons of all species in the study were found to be persistent and possess a distinctive tip probably resulting from the site of attachment to the endosperm. These distinctive, persistent cotyledons and other clearly identified morphological features, allow to readily distinguish between plumular and adventitious shoots.
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Plenzler, Michael A. "Seedling Recruitment and Establishment of Lupinus perennis in a Mixed-Management Landscape." Bowling Green State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1214238925.
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Donath, Tobias W. [Verfasser]. "Effects of ground cover on seedling emergence and establishment / Tobias W. Donath." Gießen : Universitätsbibliothek, 2013. http://d-nb.info/1065184263/34.
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Ye, Nenghui. "Stress perception and ABA signaling in rice seed germination and seedling establishment." HKBU Institutional Repository, 2011. https://repository.hkbu.edu.hk/etd_ra/1305.
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Chambers, Jeanne C. "Disturbed Alpine Ecosystems: Seedling Establishment of Early and Late Seral Dominant Species." DigitalCommons@USU, 1987. https://digitalcommons.usu.edu/etd/6370.
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This study examined the effects of seedbed and seedling environment on establishment of early and late seral dominant alpine species. Species studied included late seral dominant forbs (Geum rossii, Artemisia scopulorum, and Polemonium viscosum), early seral dominant forbs (Potentilla diversifolia and Sibbaldia procumbens), a late seral dominant grass (Festuca idahoensis), and early seral dominant grasses (Calamagrostis purpurascens and Deschampsia cespitosa). Germination responses of each species to wet vs. dry cold stratification and light vs. dark conditions were investigated. No statistical differences were observed in the seed germination of early and late seral dominant forbs or early and late seral dominant grasses, but significant differences were observed in the responses of grasses and forbs. Seed germination of forbs was greater under light than dark conditions and following wet cold storage.
Effects of fertilization on growth responses and nutrient uptake of G. rossii and D. cespitosawere evaluated in a factorial greenhouse experiment in which seedlings of each species were grown at four levels of nitrogen (N) and phosphorous (P). The late seral dominant forb responded more like a species from a low-nutrient environment exhibiting lower relative growth rates, higher root:shoot ratios, and a smaller response to N than the early seral dominant.
A field experiment on the Beartooth Plateau, Montana, examined the soil environment and seedling emergence, growth, and survival of seeded early and late seral dominants on loamy sand soils of a severe disturbance and on peat soils of an undisturbed area during two growing seasons. Effects of fertilizer and mulch were examined on the severely disturbed area. Differences between uncleared turf and turf cleared of vegetation (gap disturbance) were evaluated on the undisturbed area. The gap disturbance had higher levels of N and P and warmer soil than the severe disturbance or vegetated undisturbed area. Soil water potentials were never low enough to result in plant stress. Seedling growth was slow - .005 g to .04 g dry weight the first growing season and .02 g to .20 g the second growing season. Growth was greatest on the gap disturbance and on fertilized plots of the severely disturbed area. Early seral dominants had the largest seedlings and the smallest R/R+S ratios. Mortality was low - odds of .50 were rarely exceeded even after two years. Survival was higher on warm, nutrient rich soils of the gap disturbance. Mulch increased emergence and survival on the severe disturbance. Fertilization increased mortality, probably because an initial pulse of N was followed by a rapid decline. Higher mortality occurred in 1986 than 1985 as 1986 had a shorter growing season and cooler air and soil temperatures early in the growing season.
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Sodja, Eric P. "Effects of Soil-Borne Pathogens on Seedling Establishment Patterns in Forest Systems." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7703.
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The Janzen-Connell mechanism is proposed to maintain plant diversity: predators and diseases of seeds reduce the number of seeds that survive near a parent tree, but allow seeds far from the parent tree to grow into adulthood. In the area where seeds don’t survive, seedlings from other tree species which are not affected by the seed consumer can grow. At large scales, this effect is thought to increase overall plant diversity. Soil-borne pathogens can contribute to seed mortality in this way, but we don’t know how important different parts of their lifecycle are in creating Janzen-Connell patterns. To determine the role of soil-borne pathogens in the development of Janzen-Connell patterns, we constructed a simulation model to examine how tree and pathogen characteristics affect plant spatial patterns. Under specific combinations of tree and pathogen characteristics, we found that pathogens could create Janzen-Connell patterns. The most important parameters were how far trees dispersed their seeds, and how many seeds a tree produced in a year. These characteristics determined how much of an impact the pathogens were able to have on the tree population because they rely on the density of seeds to determine how far they can spread and how many spores they will produce.
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Norberg, Gisela. "Steam treatment of forest ground vegetation to improve tree seedling establishment and growth /." Umeå : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2000. http://epsilon.slu.se/avh/2000/91-576-6054-9.pdf.
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Lönnberg, Karin. "Effects of seed size and habitat on recruitment patterns in grassland and forest plants." Doctoral thesis, Stockholms universitet, Botaniska institutionen, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-82384.
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A trade-off between seed size and seed number is central in seed ecology, and has been suggested to be related to a trade-off between competition and colonization, as well as to a trade-off between stress tolerance and fecundity. Large seeds endure hazards during establishment, such as shading, drought, litter coverage and competition from other plants, better than do small seeds, due to a larger amount of stored resources in the seed. Small seeds, however, are numerous and small-seeded species are therefore more fecund. Moreover, a pattern with small-seeded species being associated with open habitats and large-seeded species being associated with closed habitats has been reported in the literature. In this thesis I assess effects of seed size on recruitment, and how relationships between seed size and recruitment may relate to habitat conditions. Seed sowing experiments were performed in the field to assess inter- and intra-specific relationships between seed size and recruitment in open and closed habitats (Paper I and II). Seed removal experiments were performed in the field to assess what effects seed predation may have on a relationship between seed size and recruitment (Paper III). A garden experiment was performed based on contests between larger-seeded and smaller-seeded species, in order to examine different models on co-existence of multiple seed size strategies. The results showed that there was a weak positive relationship between seed size and recruitment in the field, and that this relationship was only weakly and inconclusively related to habitat (Paper I and II). Seed removal was negatively related to seed size in closed habitats and unrelated to seed size in open habitats (Paper III). This indicates that any positive relationship between seed size and recruitment may be an effect of higher seed removal in small-seeded species. However, when grown under controlled conditions in a garden experiment, there was a clear advantage of larger-seeded species over smaller-seeded species (Paper IV). This advantage was unaffected by seed density, indicating that there was no competitive advantage of the larger-seeded species. Instead, indirect evidence suggests that larger-seeded species exhibit higher tolerance to stress.<br><p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Accepted.</p><p> </p>
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Stomph, Tjeerd Jan. "Seedling establishment in pearl millet (Pennisetum glaucum (L.) R.Br.) : the influence of genotype, physiological seed quality, soil temperature and soil water." Thesis, University of Reading, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276632.
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Moore, Patrick Terrence. "Seedling establishment guidelines for the reintroduction of American chestnut in the central hardwood region /." Available to subscribers only, 2006. http://proquest.umi.com/pqdweb?did=1136089631&sid=14&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Peterson, Jennifer Mcclain. "Ecological interactions influencing Avicennia germinans propagule dispersal and seedling establishment at mangrove-saltmarsh boundaries." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4562.
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Mangroves and saltmarshes are ecologically important coastal ecosystems; unfortunately, these low-lying coastal ecosystems are vulnerable to global climate change. As sea-levels rise, mangroves are expected to shift their distribution landward towards higher elevation sites that are occupied by other plants, including saltmarsh taxa. Therefore, mangrove recruits at the leading edge of expansion may interact with diverse assemblages of saltmarsh plants, and these interactions could influence the success of mangrove encroachment into higher tidal-elevation areas. The purpose of the research presented here was to investigate empirically the ecological interactions that may influence the recruitment of the black mangrove, Avicennia germinans, into saltmarsh habitats. Saltmarsh plants frequently occurred at the landward boundary of mangrove forests at two sites selected for field studies along the west coast of Florida: Cannon Island and Upper Tampa Bay Park.
On Cannon Island, two different field tests investigated mangrove propagule entrapment and dispersal within saltmarsh vegetation. In the first experiment, the entrapment of mangrove propagules within saltmarsh plants, exhibiting different growth forms, was examined during seasonal high tide events. Natural polyculture plots retained a mean (±;SE) 59.3% (±;11.0) of emplaced propagules. Monocultures varied in their propagule retention capacities with plots of S. virginicus retaining on average 65.7% (±;11.5) of transplanted propagules compared to 7.2% (±;1.8) by B. maritima and 5.0% (±;1.9) by S. portulacastrum. Monocultures of the salt marsh grass, Sporobolus virginicus, and natural saltmarsh polycultures containing S. virginicus retained significantly more propagules than either of two succulent plants (i.e., Batis maritima and Sesuvium portulacastrum). Using digital images, saltmarsh plant structure was quantified; the number of entrapped mangrove propagules displayed a significant and positive correlation (r2 = 0.6253, p = 0.00001) with the amount of structure provided by saltmarsh plants. Therefore, the first field study identified structural and functional differences between saltmarsh plants.
A second field study employed marked propagules in order to further examine the dispersal patterns of propagules at saltmarsh boundaries comprised of plants with different growth forms (i.e., grass vs. succulent) during seasonal high tides. Saltmarsh plant boundaries erected by taxa with distinct growth forms differentially influenced the proportion of propagules that dispersed seaward and the distance propagules moved seaward. In fact, nearly twice as many propagules dispersed seaward at boundaries erected by succulent plants compared to boundaries composed of grass. The results of this field study support my previous findings that propagule dispersal is comparatively lower in saltmarsh grass than in succulent saltmarsh plants. The findings from these two field studies suggest that the permeability of boundaries formed by saltmarsh plants may modulate landward dispersal of A. germinans propagules.
The final field study was conducted at Upper Tampa Bay Park, where a second species of saltmarsh grass, Monanthochloe littoralis, co-occurred with the grass, S. virginicus, and succulent saltmarsh plants to form a mosaic landscape of saltmarsh plant patches. Patches were weeded to create 3 saltmarsh treatments: 1) M. littoralis monoculture; 2) S. virginicus monoculture; and 3) polycultures containing both grasses and at least one other saltmarsh taxa. Propagules of A. germinans were emplaced into saltmarsh patches and followed for 11 weeks. On the last sampling date, the greatest number of A. germinans (n = 51) had successfully established as seedlings within the M. littoralis monoculture plots. In contrast, only 20 (22% of the propagules initially emplaced) A. germinans seedlings established in S. virginicus monoculture plots. These findings suggest that among grass taxa, species identity influences mangrove establishment success, which builds upon our previous findings that demonstrated that saltmarsh growth form (i.e., grass vs. succulent) influenced mangrove propagule dispersal.
Combined the findings from these field studies indicate that interactions among the early life history stages of black mangroves and neighboring plants influence mangrove recruitment. Specifically, these field studies provide empirical evidence that the species composition of saltmarsh plants influences mangrove propagule dispersal and seedling establishment. The work presented here has implications for understanding the suite of ecological interactions that may influence mangrove encroachment into saltmarsh habitats at higher tidal elevations as sea-levels rise.
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Lett, Signe. "Mosses as mediators of climate change : implications for tree seedling establishment in the tundra." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-130942.
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Alpine and arctic tree line expansion depends on the establishment of tree seedlings above the current tree line, which is expected to occur with climate warming. However, tree lines often fail to respond to higher temperatures. Other environmental factors are therefore likely important for tree seedling establishment. Above the tree line, establishing seedlings encounter existing vegetation such as bryophytes, which often dominate in arctic and alpine tundra. Bryophytes modify their environment in various ways and may mediate climate change effects on establishing tree seedlings, and with that tree line expansion. The aim of this thesis was to understand if and how the environment, in particular bryophytes, mediates the impact of climate change on tree seedling establishment at the alpine and arctic tree line. This was explored by reviewing literature on tree seedling establishment at alpine and arctic tree lines globally. In addition, tree seedling survival and growth of Betula pubescens and Pinus sylvestris were assessed experimentally. Here, individuals were planted into mono-specific mats of different bryophytes species and exposed to warming and different precipitation regimes. The literature review revealed that besides from temperature, tree seedling establishment is affected by a wide range of abiotic and biotic factors including water, snow, nutrients, light, disturbance and surrounding vegetation. Furthermore the review revealed that for example vegetation can change tree seedling responses to climate change. The experiments showed that especially tree seedling survival was adversely affected by the presence of bryophytes and that the impacts of bryophytes were larger than those of the climate treatments. Seedling growth, on the other hand, was not hampered by the presence of bryophytes, which is in line with earlier findings that seedling survival, growth and seed germination do not respond similarly to changes in environmental conditions. Moreover, we found several indications that vegetation above the tree line, including bryophytes, mediated tree seedling responses to warming and precipitation or snow cover. This thesis shows that temperature alone should not be used to predict future tree seedling establishment above the alpine and arctic tree line and that extrapolations from climate envelope models could strongly over or under estimate tree line responses to warming. This underlines the value of multi-factorial studies for understanding the interplay between warming and other environmental factors and their effects on tree seedling establishment across current tree lines.
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West, Lee. "Effects of Soil Fungi on Tree Seedling Establishment in a Southeastern Coastal Plain Forest." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/46180.
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Effects of fungi and overstory composition on tree seedling survival and growth were investigated in closed canopy upland forests in the coastal plain of South Carolina. Seedlings of Quercus alba, Cornus florida and Pinus taeda were planted in the understory of two forest types -naturally regenerated hardwood and planted pine. Fungal species composition and biomass were experimentally manipulated with a treatment of the fungicide captan.
In contrast with other studies conducted in different systems (sand dune, grassland, and old field), the effects of soil fungi were minor in a closed canopy forest. Only Q. alba showed a significant response to the fungicide (p < 0.05) treatment with increased growth.
Overstory composition had no significant effect on growth or survival for any of the species. Both of the commercially desirable species (Q. alba and P. taeda) had reasonable survival ( @ 60%). Both also maintained positive, though modest, growth. This suggests that an advance regeneration pool could be established successfully by artificial regeneration.<br>Master of Science
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Wenk, Evelyn Susannah. "Effects of vegetation structure on fire behavior and wiregrass seedling establishment in xeric sandhills." Connect to this title online, 2009. http://etd.lib.clemson.edu/documents/1252423837/.
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Woods, Steven Richard. "Woody plant proliferation in desert grasslands: perspectives from roots and ranchers." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/321001.
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The widespread proliferation (or 'encroachment') of trees and shrubs in grasslands over the past 150 years is embedded in both natural and human systems. This dissertation addressed the following ecological and ethnoecological questions. Can seedling traits help us understand why so few woody species have encroached markedly into North American desert grasslands, and the conditions likely to promote their proliferation? What is the role of informal knowledge of the environment in efforts to manage woody plant abundance? Woody seedling survival often depends on rapid taproot elongation. In glasshouse experiments, initial water supply markedly affected taproot elongation in young seedlings. Response patterns may help explain recruitment patterns in Larrea tridentata, the principal evergreen woody encroacher in Sonoran and Chihuahuan Desert grasslands, and in Prosopis velutina and Prosopis glandulosa, the principal deciduous woody encroachers in Sonoran and Chihuahuan Desert grasslands, respectively. P. velutina and P. glandulosa showed greater sensitivity to water supply levels at the seedling stage than did the similar, related non-encroachers, Acacia greggii, Parkinsonia florida and Parkinsonia aculeata . This enabled the Prosopis species to overcome lower seed and seedling biomass to achieve similar taproot length to A. greggii and the Parkinsonia species. Consequently, population level advantages of lower seed mass, such as high seed numbers, may enhance encroachment potential in the Prosopis species without being negated by corresponding seedling survivorship disadvantages. I used semi-structured interviews to document informal rangeland monitoring by ranchers in southeast Arizona. Ranchers used qualitative methods to assess forage availability, rangeland trends and responses to woody plant suppression measures. Informal rangeland assessments informed ranchers' management decisions on sub-yearly, yearly and multi-year timescales. Informal monitoring appeared largely compatible with formal monitoring and natural science, and most ranchers integrated the two systems. Informal rangeland assessments can be valuable in planning woody plant suppression measures, particularly in light of the small number of formal long-term studies of brush suppression. Ecological studies may help predict places and periods of relatively rapid encroachment, perhaps enabling early or pre-emptive brush suppression measures. Thus, both seedling ecology and informal environmental knowledge are likely to be useful in managing woody plant populations in desert grasslands.
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Cohen, Susan Alese. "Regenerating Longleaf Pine on Hydric Soils - Short-Term Effects on Soil Properties and Seedling Establishment." NCSU, 2008. http://www.lib.ncsu.edu/theses/available/etd-04282008-191226/.
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Restoring longleaf pine ecosystems is essential for managing rare plant and animal species and protecting biological diversity in the southeastern Coastal Plain of the United States. Natural longleaf pine ecosystems range from xeric uplands to poorly-drained flatwoods and savannas. Most existing stands, however, occur on xeric to dry-mesic sites and approaches to restoring longleaf pine to wetter sites traditionally utilize intensive practices. There is little information available on the efficacy of these practices to establish longleaf pine seedlings on poorly-drained sites and their impacts on soil properties, seedling survival and growth, and the understory plant community. A research project was established at Marine Corps Base Camp Lejeune, NC to evaluate the effects of site preparation methods for returning longleaf pine on hydric soils with no natural seed source. Various site preparation treatments were evaluated in a field experiment, and results revealed greater growth and earlier emergence from the grass stage with more intensive site preparation. There was a marginal increase in soil nutrients, and a slight increase in foliar nutrients found with the more intensive treatments. Site preparation influenced seedling growth in the short-term and this was likely due to the cumulative effects of controlling competition and modifying the planting site. Marine Corps Base Camp Lejeune and other Department of Defense installations include both former and remnant longleaf pine ecosystems that support federally protected plants and animals such as the red-cockaded woodpecker - and thus face the challenge of restoring former, poorly-drained longleaf pine ecosystems. A land use history revealed that, largely due to its poorly-drained status and inaccessibility, the majority of disturbance on the research area occurred after the 1920âs and was largely due to forestry activities. Since purchasing the land area of the project in 1996, the Marine Corpsâ challenge has been to balance the mission of training and readiness with the need for restoration and long-term management of longleaf pine ecosystems. The results of this work provide natural resource managers with a scientific foundation for assessing choices to assist in this restoration and management effort.
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Woods, Natasha Nicole. "The Relative Importance of Abiotic and Biotic Factors for Seedling Establishment in the Colorado Desert, CA." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429882344.
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Salazar, Ana. "Seed Dynamics and Seedling Establishment of Woody Species in the Tropical Savannas of Central Brazil (Cerrado)." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_dissertations/371.
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Studies of seed dynamics and seedling establishment at the community level in savanna ecosystems are scant, particularly in the tropical savannas of Central Brazil. The Brazilian savannas (cerrado) have the largest diversity of plant species among Neotropical savannas. Cerrado vegetation exhibits consistent changes in tree density and tree size along shallow topographic gradients. Vegetation types differ from closed savannas with high tree density, and a nearly continuous canopy cover in the uppermost portions, to open savannas with scattered short trees in the low portions of the topographic gradients. Whether or not dynamics of seeds and seedlings of woody species are consistent with variations in tree density and tree canopy cover across the cerrado landscape has not been determined, but could potentially influence such spatial patterns of tree density and canopy cover. The main objective of this study was to evaluate seed dynamics (i.e., seed rain, soil seed banks, and seed characteristics) and seedling establishment of woody species in three major cerrado vegetation types (closed, intermediate and open savannas) which differ in tree canopy cover and tree height. These vegetation types are located along topographic gradients of approximately 30 m in elevation and 1000 m in length. I conducted field work from June 2005 to August 2008 at the Instituto Brasileiro de Geografia e Estatística (IBGE) reserve, a field experimental station located 35 Km south of Brasilia, Brazil (15˚ 56' S, 47˚ 63' W, altitude 1100 m). I established permanent plots in each of the three vegetation types to assess seed rain, seed limitation, seed predation, and seed removal. I also quantified density and composition of the soil seed bank in each vegetation type and studied seed characteristics (i.e., kind of dormancy, moisture content, longevity) of 14 common cerrado woody species. In the field, I quantified establishment of woody seedlings in fire-protected savannas as well as in accidentally burned and frequently burned savannas. In the greenhouse I performed experiments to evaluate the effect of litter cover and light level on seedling emergence of 9 common cerrado woody species. Finally, I evaluated the effect of pulses of heat on seed germination of 5 common cerrado woody species under controlled conditions. The overall results of this study show that regardless of tree canopy cover, cerrado vegetation types are limited in seeds and seedlings of woody species, but these limitations are higher in open than in closed savannas. Most woody species do not form persistent soil seed banks along cerrado vegetation types because their seeds are short-lived, predated and quickly removed from the ground. In addition, dispersal season and dormancy appear to control timing of germination at the onset of the rainy season to ensure survival of seedlings in the field. In the absence of fire, establishment of woody seedlings is higher in closed than in open savannas because canopy cover mitigates the stressful environmental conditions of open savannas and thus facilitates establishment of woody seedlings. As a result, closed savannas are likely to maintain higher density of woody elements over time than open savannas. In burned savannas, however, species composition of woody and herbaceous seedlings is significantly affected because establishment of seedlings of woody and herbaceous species decreases but vegetative reproduction increases. This dissertation study indicates that interactions of early life-history stages of woody species with environmental and disturbance factors appear to play a more significant role in maintaining woody cover variations along cerrado topographic gradients than previously recognized.
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Kilroy, Hayley A. "Enrichment planting of an understory palm: Effect of microenvironmental variables on seedling establishment, growth, and survival." Miami University Honors Theses / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=muhonors1209495979.
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Bertacchi, Maria Isabel Ferreira. "Micro-sítio como filtro para o estabelecimento de regenerantes arbóreos em áreas restauradas." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/11/11150/tde-14022012-093157/.
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As características da regeneração natural no sub-bosque de comunidades florestais em processo de restauração expressam os principais indicadores de sucesso dos projetos de restauração ecológica, sendo que a ausência ou a baixa qualidade de regeneração natural são os principais gargalos para a perpetuação de projetos inseridos em paisagens muito fragmentadas. No entanto, condições adversas de micro-sítio de regeneração sob plantios de restauração podem restringir a colonização do sub-bosque por espécies nativas, comprometendo a sua perpetuação no tempo. O objetivo desse estudo foi avaliar se, e como, as condições físico-químicas do micro-sítio de regeneração, no sub-bosque de áreas em processo de restauração com diferentes idades, podem limitar o estabelecimento de espécies arbóreas nativas, restringindo assim, a restauração da dinâmica florestal. O estudo foi desenvolvido em três áreas em processo de restauração com diferentes idades (10, 22 e 55 anos), implantadas via reflorestamentos de alta diversidade. Foi realizada a caracterização físico-química do micro-sitio de regeneração das áreas de estudo, avaliando-se o grau de compactação, porosidade, umidade, conteúdo de matéria orgânica e nutrientes e granulometria do solo, bem como a massa seca de serapilheira, e a cobertura do dossel. Em cada área de estudo, foram alocados 10 blocos experimentais, cada um constituído por 4 parcelas de 1 m x 1 m, onde foram semeadas nove espécies arbóreas nativas regionais. Nessas parcelas foram estabelecidos três tratamentos e um controle: A) semeadura na condição natural da área, sem qualquer alteração das características do micro-sítio de estabelecimento (serapilheira autóctone), B) semeadura sobre a serapilheira e o solo transplantados de floresta nativa (serapilheira alóctone), C) semeadura sobre bagaço de cana triturado e compostado e D) controle (sem semeadura). A coleta dos dados de emergência e mortalidade de plântulas foi feita por um período de 6 meses. Ocorreu um gradiente de aumento da cobertura do dossel, da porosidade, da umidade, do conteúdo de argila e matéria orgânica e uma diminuição da compactação do solo das áreas restauradas mais novas para as mais velhas. A emergência de plântulas não diferiu entre as áreas de estudo, porém, a sobrevivência de plântulas foi significativamente menor na restauração mais antiga, de 55 anos. Constatou-se uma correlação positiva entre a mortalidade de plântulas com o aumento da cobertura do dossel e com a quantidade de matéria orgânica no solo. A emergência e a sobrevivência de plântulas foram estatisticamente maiores no tratamento onde as sementes foram aplicadas sobre serapilheira autóctone. Assim, conclui-se que apesar das condições de micro-sítio de regeneração de florestas em restauração tornarem-se, com o tempo, mais semelhantes à de florestas naturais, tornam-se cada vez mais restritivas ao estabelecimento de plântulas. Além disso, o estabelecimento de plântulas é favorecido nas condições locais de substrato de florestas em processo de restauração florestal, sem limitação evidente para que a sucessão secundária avance. Conseqüentemente, a limitação de dispersão deve ter influência maior nessas condições para o avanço inicial da restauração do que a limitação de micro-sítios favoráveis de estabelecimento.<br>The characteristics of the natural regeneration of restoration plantings understory express the main indicators of success of ecological restoration projects, in which the absence of regeneration indicates a bottleneck for the perpetuation of forest communities inserted into highly fragmented landscapes. Nevertheless, adverse conditions of the micro-site of regeneration in restoration plantings may hamper the colonization of the understory by native species, which in turn collapse its perpetuation along the time. We sought to evaluate if, or how, the physical-chemical conditions of the micro-site of regeneration of restoration plantings with different ages can limit native tree species establishment and therefore, the dynamic of forest restoration. The study was developed in three areas under restoration with different ages (10, 22 and 55 years). The physical-chemical characterization of the micro-site of regeneration of the study areas was carried out by evaluating the soil compression level, porosity, humidity, organic matter and nutrients content and granulometry, as well as litter dry mass and canopy cover. In each area, we set 10 experimental blocks, each one consisting of four 1 m x 1 m plots, in which nine tree species were sown. In each plot we established three treatments: A) direct seeding in the natural condition of the area, without any alteration in the characteristics of the micro-site (indigenous leaf litter), B) direct seeding on the leaf litter and soil transplanted from a native forest (allochthonous leaf litter), C) direct seeding on grounded and composted sugarcane bagasse and D) control (no seeding). Seedling emergence and mortality were observed through six months. An increase on the canopy cover and soil porosity, humidity, clay and organic matter content were observed in the oldest areas, as well as a decrease in soil compression. Seedling emergence did not differ among the studied areas; however, seedling survival was significantly lower in the oldest reforestation, with 55 years. A positive correlation was observed between seedling mortality with the increase of canopy cover and soil organic matter content. Seedling emergence and survival were statistically higher in the treatment A (indigenous leaf litter). Thus, although the micro-site conditions for seedling establishment become even more similar to reference ecosystems as restoration planting evolve, it also becomes more restrictive. In addition, seedling establishment was favored in the conditions of local substrate of restoration plantings, without evidence of limitation for the progress of secondary succession. Consequently, dispersal limitation may play a higher influence in this condition for the advance of restoration process.
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Peña, Ahumada Andrea Alejandra. "Antioxidant defence and the role of the peroxiredoxins during silique development and seedling establishment in oilseed plants." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=980373115.
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Li, Fui Yee. "Factors affecting tree seedling establishment following rehabilitation management in logged-over tropical rain forest in Sabah, Malaysia." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429982.
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Allen, Elizabeth Jane. "Global investigations into the metabolic regulation of gene expression during germination and seedling establishment in Arabidopsis thaliana." Thesis, Bangor University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488845.
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Liu, Rui. "Regulation and molecular signaling during seed germination and seedling establishment of arabidopsis in response to abiotic stresses." HKBU Institutional Repository, 2013. https://repository.hkbu.edu.hk/etd_oa/101.
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Plants regulate many physiological processes in response to adverse environmental stresses. This study focused on the seed germination and seedling establishment stage and investigated the molecular signaling events when abiotic stresses, such as osmotic, water and temperature, were applied. Seeds of Arabidopsis, mutants or wild type, were used to identify the signaling components. Cold-pretreatment (stratification) is widely used to break seed dormancy and improve germination rate. Stratification at 4. significantly broke the seed dormancy of Arabidopsis in wild-type, cyp707a2, sleepy1 and sleepy1/cyp707a2, but not in ga3ox1. Stratification and exogenous ABA treatment strongly enhanced the expression and the activity of a-amylase in the freshly harvested seeds among the wild-type and those mutants, which have relatively high ABA content. Similarly, the expression of RGL2 and ABI5 were also substantially suppressed by stratification. These results suggest that stratification firstly leads to GA biosynthesis and unlocks the inhibition of RGL2 on the expression of a-amylase. Stratification also relieves the inhibition of ABA on the germination process but the inhibition of ABA on seedling development is not affected. We have isolated an Arabidopsis mutant, dsptp1, which is hyposensitive to osmotic stress during seed germination and seedling establishment, indicated by exhibiting higher seed germination rate, lower inhibition in root elongation under osmotic stress, and more tolerance to drought compared with the wild type (Col0) plants. Osmotic stress and drought enhanced AtDsPTP1 expression in seed coats, the bases of rosette leaves and roots. Compared with the wild type, the dsptp1 mutant increased proline accumulation, reduced MDA content and ion leakage, and enhanced antioxidant enzyme activity under osmotic stress. AtDsPTP1 regulated the transcript levels of various dehydration responsive genes, ABA biosynthesis and metabolic enzyme gene under osmotic stress, resulting in reduced accumulation of ABA in dsptp1 mutant plants than wild type in response to osmotic stress. AtDsPTP1 also mediated the ABA signaling pathway under osmotic stress by suppressing the expression of ABI1 and enhancing the expression of the positive regulators ABI3 and ABI5 in ABA signaling. These data suggest that AtDsPTP1 positively regulates ABA accumulation and signaling during seed germination and seedling establishment in Arabidopsis under osmotic stress. To further investigate the regulation mechanism of DsPTP1 in osmotic stress and drought signaling, we analyzed the water holding capacity between wild type and dsptp1 mutant. The dsptp1 mutant exhibited enhanced water holding capacity compared to wild type under osmotic stress resulting from reduced water loss and increased relative water content, which shall contribute the osmotic and drought tolerance. To identify the signaling components, we investigated the activity of MAPKs under osmotic and drought stress and found that the DsPTP1 differentially regulates the activities of MAPK6 and a p38 MAPK, which is inferred as MAPK12 according to its molecular weight in Arabidopsis under osmotic and salt stress. However, there is no direct interaction between DsPTP1 and 20 MAPKs indicated by the results of the of specific interaction test. These results suggest that the differential regulation of MAPK6 and MAPK12 by DsPTP1 is indirect. In addition, we screened the interaction proteins of DsPTP1 under abiotic stress. Seventeen positive clones were acquired from the sequencing results. More work need to be done to confirmed the positive interactions and the signaling cascades. In summary, seed germination and seedling growth are closely regulated by environmental cues. This should be the result of evolutionary selection since successful new growth from the seed embryo depends on the sensitive perception of environmental conditions and effective regulation of many physiological processes that are involved. We have demonstrated that plant hormones, especially ABA, play central regulative roles during such regulations. Many other signaling components, such as protein kinases and phosphatases, are also involved. Identifying the detailed signaling pathways should be the focus of further research.
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Camu, Isabelle Veronique Marie. "Understanding the mechanism(s) of hydro-priming to improve seed vigour and seedling establishment of Solanum lycopersicum." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/33211.
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Seeds are very complex and diverse plant organs. Seed germination is the most sensitive stage of plant life and is influenced by various environmental signals including phytohormones, salt, light, temperature and water potential. Seeds have an innate mechanism called dormancy that blocks germination, and plants have developed several dormancy-inducing strategies to optimise the timing of germination. Seed germination vigour is an important factor in crop yield. Seedling vigour is defined as the sum of the seed properties which determine the level of activity and performance during germination and seedling emergence. A poor seed lot can be improved by post-harvest treatment such as hydro-priming as it is used in the seed industry, but the biological mechanism is unknown. The aim of this study is to understand the mechanism(s) of hydro-priming in order to improve seed vigour and seed germination. I set seeds at different temperatures to produce variation in seed vigour and it showed that germination of seeds with low vigour can be improved by hydro-priming. Using LC-IT-ToF/MS I characterised compounds that leach from seeds during hydro-priming, and showed that some of these are putative germination inhibitors. Adding these compounds to the water during hydro-priming showed that the inhibitory effect of these compounds is not the main mechanism that regulates germination. Also, transcriptomic analysis showed that genes involved in OPDA pathway are expressed during hydro-priming as well as during endosperm weakening cap associated genes. I concluded that hydro-priming improves the speed of germination of low temperature set and its efficiency is dependent of activation of metabolic activity.
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Giolo, Maurizio. "Germination, seedling growth and establishment of warm-season turfgrasses related to climate changes in the Mediterranean region." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3422696.
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The Mediterranean region is located from the arid climate of North Africa up to the temperate and rainy climate of northern and central Europe. Climate simulations show a gradual increase in heating, drying and precipitation variability in this region. These effects will probably push warmseason turf species towards minor latitudes. The consequences of climate change on turfgrass management have been investigated only recently. Germination and seedling growth have also been little studied for the response to climate change effects, although the establishment phase is central to any high-performing turfgrass. For warmseason grasses in the transition zone, a quick establishment increases winter survival and allows for earlier spring green-up and a more rapid recovery from winter injury. In the Mediterranean region, warm-season grasses are commonly seeded in late spring when the
temperatures are suitable for a rapid establishment. Warm-season species used extensively by the turf industry have fertile and sterile cultivars. Seeded cultivars are usually preferred over sterile cultivars because seeding is cheaper and easier to practice than vegetative propagation methods which include plugging, sprigging, and stolonizing. The present study concerns two of the most used warm-season turf species in the Mediterranean
area: Bermudagrass (Cynodon spp.) and seashore paspalum (Paspalum vaginatum Swartz) and one potential future new species i.e.buffalograss [Buchloe dactyloides (Nutt.) Engelm.]. The research activity scheduled consisted of five experiments conducted in the field and controlled environments (growth chamber and greenhouse) to investigate the effects of suboptimal temperatures and excess of water due to flooding on seed germination and seedling growth. The main results were the following: Effects of sub-optimal temperatures The warm-season grasses tested germinated at a temperature equal or higher than 11.4 °C (base germination temperature) and early April is the optimal seeding time for establishing by seed warmseason turfgrasses in the Po-Venetian valley. From these results, we have concluded that the predicted warmer springs should lead to earlier seeding of warm-season grasses favouring turfgrass maturation before winter. Effects of water excess All three warm-season turf species under study tolerate flash waterlogging. However, bermudagrass is the one less affected by prolonged waterlogging (6-8 days). In general, warm-season grasses can be successfully used for establishing turfgrasses considering the future climate change predicting the increase of extreme precipitation events.<br>La regione mediterranea è ubicata fra il clima arido del Nord Africa ed il clima temperato e piovoso dell'Europa settentrionale e centrale. Le previsioni sui cambiamenti climatici nei prossimi anni presentano un graduale aumento delle temperature e delle condizioni di aridità, come pure l’aumento di eventi piovosi intensi e localizzati. Per effetto di questi cambiamenti climatici si prevede un crescente impiego di specie macroterme (C4) a latitudini minori comprese quelle utilizzate per la formazione di tappeti erbosi. Le conseguenze sulla gestione del tappeto erboso sono state studiate solo di recente ed inoltre mancano risultati scientifici riguardo gli effetti prodotti dai cambiamenti climatici sulla germinazione e sulle prime fasi di crescita delle plantule. Nella regione mediterranea, le poacee macroterme vengono seminate in tarda primavera, quando le temperature consentono una pronta germinazione ed un rapido insediamento del tappeto erboso. Queste specie presentano sovente cultivar fertili e cultivar sterili che possono essere insediate unicamente per via vegetativa (plugging e stolonizzazione). Le cultivar da seme sono generalmente preferite alle cultivar sterili essendo la semina più economica e più facile da praticare di un insediamento per via vegetativa. Le fasi di insediamento del tappeto erboso seminato sono particolarmente importanti nella gestione dei tappeti erbosi in zone di transizione. Un rapido insediamento, infatti, consente alle specie macroterme di affrontare in condizioni ottimali i rigori invernali e riprendere rapidamente a vegetare in primavera. Il presente studio ha preso in esame due delle specie macroterme da tappeto erboso più utilizzate nell’area mediterranea: gramigna (Cynodon spp.) e paspalum vaginatum (Paspalum vaginatum Swartz) e una specie che potrebbe trovare possibilità di impiego nei prossimi anni e cioè buffalograss [Buchloe dactyloides (Nutt.) Engelm.]. L’attività di ricerca nell’ambito del dottorato prevedeva cinque esperimenti condotti in campo e in ambiente controllato (camera di crescita, serra), finalizzati allo studio degli effetti delle temperature sub-ottimali e dell’eccesso idrico, dovuto ad eventi piovosi intensi, sulla germinazione dei semi e sulla crescita delle plantule delle suddette specie macroterme. I risultati più significativi sono di seguiti riportati. Effetti di temperature non ottimali È stato dimostrato che la germinazione delle specie macroterme testate avviene solamente quando la temperatura è uguale o superiore a 11,4 °C e che l’inizio di aprile può essere considerato il momento ottimale per la semina di tali specie nella pianura padano-veneta. L’incremento termico previsto nei prossimi anni dovrebbe consolidare tali risultati. Una semina ad inizio aprile, diversamente da quanto solitamente avviene (metà-maggio) consente di completare l’insediamento entro maggio, così il tappeto erboso avrà a disposizione l’intera estate per maturare e affrontare nel migliore dei modi l’inverno. Effetti dell'eccesso idrico. Le nostre ricerche hanno evidenziato la spiccata attitudine delle tre specie oggetto di studio a sopportare il ristagno idrico. In particolare, la gramigna è risultata la specie più tollerante all’eccesso idrico nel suolo durante l’insediamento, conservando la germinabilità ed una buona crescita delle plantule anche dopo 6-8 giorni di sommersione. In generale, possiamo affermare che le specie macroterme da tappeto erboso possono essere di grande interesse per la realizzazione di tappeti erbosi nelle condizioni prospettate dai futuri scenari legati al cambiamento climatico.
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Gurmu, Mulugeta. "The effects of seed vigour and moisture stress on the germination and seedling establishment of wheat and sorghum." Thesis, University of Aberdeen, 1991. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU031802.
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The experiments reported in this thesis assessed vigour differences between seed lots of wheat and sorghum under suboptimal conditions. A vigour assessment for each lot of both species was quantified by calculating a value for the viability equation constant Ki. Imbibition of seed lots at lower water potentials reduced water uptake, radicle and coleoptile emergence and their subsequent extension. Similarly, seeds aged by controlled deterioration also resulted in reduced radicle and coleoptile emergence and growth compared to that of unaged seeds. The critical water potential for radicle emergence, coleoptile emergence and their subsequent extension was lower for sorghum than that required for wheat. In both species coleoptile emergence and its subsequent extension was more sensitive than radicle emergence and extension. Tolerance of desiccation of both species decreased as germination progressed. However, imbibition of seeds for 24 h and drying back to their original moisture content promoted seed invigoration in some cases. Cells from seminal roots of wheat and sorghum were shorter when imbibed in lower water potentials than when they were imbibed at higher water potentials. The high drought tolerant cv (DJ1) showed lower root solute potential than the low drought tolerant cv (IS9). The results discussed in this thesis indicate that the information derived from controlled deterioration might be used as an indicator of planting value under sub-optimal conditions.
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Breen, Amanda Nicole. "Improving seedling establishment on the saline playa at Owens Lake, California through soil amendment, improved seed quality, and increased seed entrapment /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2005. http://uclibs.org/PID/11984.
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Shepherd, Ashley Lauren. "Mapping of Sonoran Desert Vegetation Communities and Spatial Distribution Differences of Larrea Tridentata Seed Density in Relation to Ambrosia Dumosa and Ambrosia Deltoidea, San Cristobal Valley, Arizona." Thesis, The University of Arizona, 2011. http://hdl.handle.net/10150/217053.
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Vegetation in the San Cristobal Valley of Barry M. Goldwater Range-East was mapped using a combination of field surveys and aerial imagery interpretation to contribute to ongoing inventory of natural resources for the BMGR-East as well as assist in resource management decisions. Eighteen vegetation associations were identified and mapped through collection of 186 samples to characterize vegetation associations. The most common vegetation association was Larrea tridentata monotype, covering 29% of the area mapped. Larrea tridentata is a widely spread shrub throughout the Sonoran, Chihuahuan and Mojave deserts; therefore understanding germination and seedling survival patterns is crucial. Ambrosia dumosa and A. deltoidea exhibit nurse plant-protégé interactions with L. tridentata. Seed density of L. tridentata was studied under Ambrosia species to determine factors controlling germination and seedling density. As expected seed density was greater under Ambrosia canopy than areas with no canopy. Ambrosia species and canopy type did not affect seed density.
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Young, Kert R. "Plant Establishment and Soil Microenvironments in Utah Juniper Masticated Woodlands." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3318.
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Juniper (Juniperus spp.) encroachment into sagebrush (Artemisia spp.) and bunchgrass communities has reduced understory plant cover and allowed juniper trees to dominate millions of hectares of semiarid rangelands. Trees are mechanically masticated or shredded to decrease wildfire potential and increase desirable understory plant cover. When trees are masticated after a major increase in tree population density and associated decrease in perennial understory cover, there is a risk that invasive annual grasses will dominate because they are highly responsive to the increased resource availability that commonly follows removal of the main resource user. To determine if tree mastication increases resource availability and subsequently favors invasive annual or perennial grasses, we compared soil temperature, water, and nutrient microenvironmental conditions and seedling establishment and growth. We used the major rangeland weed, cheatgrass (Bromus tectorum L.), to represent invasive annual grasses and Anatone bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) A. Löve), a natural accession of native bluebunch wheatgrass, to represent the perennial grasses of the sagebrush-bunchgrass plant community. These comparisons were made between and within paired-adjacent masticated and untreated areas at three locations in Utah dominated by Utah juniper (Juniperus osteosperma (Torr.) Little). Juniper tree mastication generally increased resource availability with masticated areas having greater soil temperature, soil water availability, and soil N supply rates than untreated areas. Prior to juniper tree mastication litter mounds were not found to be resource islands probably because juniper trees themselves were using subcanopy soil water and nutrients. After juniper tree mastication and elimination of these predominant resource users, litter mounds served as resource islands with greater soil water availability and N supply rates than bare interspaces during the critical time for seedling establishment in spring. Plant growth followed in line with greater resource availability after tree mastication with masticated areas having more productive although fewer invasive-annual and perennial grass seedlings than untreated areas. These results suggest that increases in resource availability and warmer spring temperatures associated with mastication will not necessarily favor invasive annual over perennial grass seedling establishment. Resilience of the sagebrush-bunchgrass community to return to dominance after juniper control will likely be greatly influenced by how much of the sagebrush-bunchgrass community remains following tree control and the intensity of propagule pressure by invasive species. If only invasive annuals remain when the trees are treated then invasive annuals would be expected to dominate the post-treatment plant community especially with their ability to establish inside litter mounds unless they were also controlled and perennial grasses planted at the time of treatment.
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Wäli, P. (Piippa). "Environment and genetic background affecting endophyte-grass symbiosis." Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514281632.
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Abstract
Mutualism is often conditional and the associations vary from antagonism to mutualism along environmental conditions and genotypes of interacting species. I studied antagonism-mutualism continuum hypothesis of symbiosis experimentally using two different Epichloë/Neotyphodium endophytes and their host grasses, agricultural meadow fescues and natural fine fescue, as study systems. These systemic fungal endophytes live asymptomatically within aerial tissues of grasses, and are vertically transmitted to the next grass generation via seeds. Thus, asexual endophyte strains are dependent on the growth, survival and reproduction of their hosts. Epichloë/Neotyphodium endophytes are considered plant mutualists, because they improve the resistance of the host against various stresses, e.g. herbivores. In addition to experimental approach, I examined prevalence and genetic structure of Epichloë festucae in natural grass populations. Finally, current knowledge concerning grass endophytes was reviewed and the effects of variable environment and genetic background on the ecology and the evolution of grass-endophyte symbiosis were discussed.
The endophyte improved the performance of the agronomic meadow fescues, but the beneficial effects were dependent on the grass cultivar and the growth environment. The endophyte-infected (E+) meadow fescues were more susceptible to the pathogenic snow molds and they suffered increased winter damage compared to the endophyte-free (E-) plants. Many natural Festuca rubra and F. ovina populations were either endophyte-free or had low infection frequency. The highest infection frequencies were found in subarctic areas where the infection incidence differed between habitats. Twenty out of the 25 E. festucae genotypes detected were carrying multiple alleles in microsatellite loci indicating multiple infections or vegetative hybridization of the fungus. A dominant genotype (63.5% of all isolates) occurred in all populations suggesting that this fungus is mainly asexual. E+ F. ovina seedlings performed worse than endophyte-free E- seedlings. In F. rubra, the river bank originated E+ seedlings allocated fewer, but longer and heavier tillers than the other seedlings indicating possible improved performance of the endophyte infected grasses in harsh river bank conditions.
In short, I detected both positive and negative effects of endophyte infection on grasses varying along species, environment and genotypic background of study subjects. The results support the antagonism-mutualism continuum hypothesis.
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Young, Laura May. "Seed dispersal mutualisms and plant regeneration in New Zealand alpine ecosystems." Thesis, University of Canterbury. School of Biological Sciences, 2012. http://hdl.handle.net/10092/6992.
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The New Zealand alpine zone has many fleshy-fruited plant species, but now has a relatively depauperate animal fauna. The key question is, therefore, are native alpine plants still being dispersed, if so where to and by what? I first measured fruit removal rates among nine common species using animal-exclusion cages to compare natural fruit removal by all animals, and by lizards only. Over two years, mean percent of fruit removed by early winter ranged from 25–60% among species. Speed of fruit removal also varied depending on species. Secondly, I quantified which animals disperse (or predate) seeds of those fruits, into which habitats they deposit the seeds, and the relative importance of each animal species for dispersal, in two ways. A 2-year study using fixed-area transects to monitor faecal deposition showed that introduced mammals (especially possums, rabbits, hares, sheep, pigs and hedgehogs) were abundant and widespread through alpine habitat. Of the 25,537 faeces collected, a sub-sample of 2,338 was dissected. Most mammals dispersed most (> 90%) seeds intact. However, possums (numerically the important disperser) moved most seeds into mountain beech (Nothofagus solandri) forest, while rabbits, hares, and sheep dispersed seeds mainly into open grassland dominated by thick swards of exotic grasses (e.g. Agrostis capillaris and Anthoxanthum odoratum); all are less suitable microsites. Kea (Nestor notabilis), the largest and most mobile of only three remaining native alpine bird species, are potentially useful as a long-distance seed disperser, even though parrots are typically seed predators. I found that kea are numerically more important than all other birds combined, damage very few seeds, and are probably responsible for most dispersal of seeds between mountain ranges. Finally, I investigated the effects of seed deposition microsite (shady/high-light), pulp-removal (whole/cleaned), competition (soil dug/not-dug) and predation (caged/ not) on germination, growth and survival of eight subalpine plant species. There were strong positive effects of shady microsites for seed germination and seedling survival to 3.5 years for six of the eight species. Effects of other treatments were less important and varied among species and stages. Hence, both native birds and introduced mammals are dispersing alpine seeds, but the mammals often deposit seeds in habitats unsuitable for establishment. Any evaluation of the dispersal effectiveness of frugivores must consider their contribution towards the long-term success for plant recruitment through dispersal quantity and quality.
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Gadeh, H. M. "The effect of compost and priming on the salt tolerance of bread wheat (Triticum aestivum L. cv. S-24 and cv. Slambo) during germination and early seedling establishment." Thesis, Coventry University, 2013. http://curve.coventry.ac.uk/open/items/f0bd31e5-d16c-4435-993a-ab1ec64d7bc3/1.
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Soil salinity and the arid climate in Libya are major constraints in agriculture and predominantly in foodstuff production which are limiting wheat production and yield. The effect of pre-sowing seed treatments with 50 mM of KCl, NaCl, CaCl2, and distilled water as hydropriming on germination and early seedling growth in two wheat (Triticum aestivum L.) cultivars S-24 (tolerant) and Slambo (untested before) under 0, 100, 200 and 300 mM NaCl concentrations was examined. CaCl2 was the only priming treatment that significantly improved the germination percentage, germination rate, and mean germination time in both cultivars under almost all NaCl concentrations. Thus, priming with CaCl2 was selected for further experiments. In the greenhouse, seeds primed with 50 mM of CaCl2 also improved the emergence percentage, emergence rate, shoot and root length, and fresh and dry weight of shoots and roots of both cultivars under all NaCl concentration except at 300 mM where the emergence was completely inhibited. The response of wheat cultivars to three compost treatments including cow manure compost (CC), greenwaste compost (GC) and 50:50 mixture (mix) between them and sand at percentage inclusions of 10 and 30 % by weight under 0, 100, 200, and 300 mM of NaCl was also investigated. Among all compost treatments, 30% GC and 30% mix were the best treatment and improved almost all growth parameters under salt stress, and 30% GC was also the only treatment that had any emergence at 300 mM NaCl. 30% GC and 30% mix were selected for further experiments. The effect of the combination of the selected priming agent (CaCl2) and the best two compost treatments (30% GC and 30% mix) on the emergence and early seedling growth of both cultivars was tested. The results showed that all the treatments enhanced plant growth parameters including seedling ion uptake in both cultivars, with preference to primed seeds sown in 30% GC. The treatments had the following order of the performance of both cultivars under salt stress. Primed seeds sown in 30% GC > unprimed seeds sown in 30% GC > primed seeds sown in 30% mix > unprimed seeds sown in 30% mix. This enhancement is possibly due to the provision of Ca2+ and / or the improvement in the availability of water as both of them were improved by the application of priming and compost.
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Benard, Rebecca Balogh. "Causes and consequences of spatial aggregation for seedling establishment of a long-lived desert perennial shrub (Chrysothamnus nauseosus: Asteraceae) : interaction between intrinsic properties of individuals and fine-scale environmental heterogeneity /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2005. http://uclibs.org/PID/11984.
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Shaffer, James D. "FACTORS INFLUENCING THE ESTABLISHMENT AND SURVIVAL OF NATIVE HARDWOOD TREE SEEDLINGS OF THE KENTUCKY INNER BLUEGRASS BLUE ASH-OAK SAVANNA-WOODLAND." UKnowledge, 2013. http://uknowledge.uky.edu/biology_etds/15.
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Historically, the Kentucky Inner Bluegrass blue ash-oak savanna-woodland was the primary ecosystem of the Inner Bluegrass Region (IBR) of Kentucky. After European settlement, the majority (>99%) of Bluegrass savanna was converted to agricultural and urban land uses. Currently remnant savanna tree species are failing to recruit. Therefore, a long-term restoration ecology project researching competition and disturbance on seedling establishment, survival, and growth has been established at Griffith Woods (the largest remaining savanna in Kentucky) in Harrison Co., KY. Fourteen native hardwood tree species (a total of 6,168 seedlings) have been experimentally planted. Light, soil, surrounding vegetation, and herbivory, factors thought to influence seedling survival, have been initially assessed. Results show that soils differed spatially in P, Ca, Mg, Zn, pH, N percent and soil organic matter percent. Light was significantly reduced by diffusive filtering through vegetation. Vegetation biomass was influenced by pH and Mg. Initial seedling survival was high, but significantly differed by species type, location, and soil pH, Mg, and Zn. This research demonstrates that under a similar range of conditions, native hardwood tree seedling establishment is possible. Therefore, the potential exists to restore Bluegrass savanna-woodland in order to return proper ecological functioning into a degraded landscape.
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Camp, Keri Van. "Environmental Variables that Affect the Establishment of Myrica gale Seedlings." Fogler Library, University of Maine, 2005. http://www.library.umaine.edu/theses/pdf/CampKV2005.pdf.
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Ashkenazi, Rafael 1958. "Influence of herbicides on establishment of tree seedlings in northern Israel." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/277933.
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The influence of the herbicides sulfometuron and simazine on the establishment of 8 species of tree seedlings was studied in northern Israel. The experiment included three treatments and a control. The first treatment applied simazine at a rate of 5 kg/ha, and second treatment applied simazine at a rate of 5 kg/ha and sulfometuron at a rate of 0.03 kg/ha. Sulfometuron was applied alone at a rate of 0.03 kg/ha in the third treatment. Statistical analyses showed significant effects on the survival of some species treated with sulfometuron. To ensure earlier season survival, the rate of sulfometuron applied should be kept at a minimum level to allow both weed control and adequate establishment of seedling. Low-rate applications are particularly important in arid and semi-arid areas.
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Sulaiman, Raja Barizan Raja. "Studies on the early establishment of dipterocarp seedlings in a Malaysian logged hill forest." Thesis, University of Stirling, 1997. http://hdl.handle.net/1893/21437.
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A 5.6 ha research plot in logged hill forest in central Peninsular Malaysia at Berkelah F. R., Pahang was set up to study the early establishment of dipterocarp species in the field. The site of the logged forest could be broadly grouped into three classes based on the degree of canopy opening and soil compaction: (1) categories B&A: open (25-55 % relative light intensity (RLI) as a high light level) and compacted or less compacted soil, respectively (2) category C: partial shade (8-9 % RLI as a medium) and less compacted soil, and (3) categories D&E: closed canopy (2-3 % RLI as a low light level) with high and low dipterocarp abundances, respectively. Planting trials in the field were conducted with two dipterocarp species, Hopea odorata and Dryobalanops oblongifolia. Application of Triple superphosphate (TSP), a fast-release fertiliser, (0.33 - 0.40 g per pot) in the nursery increased the P concentrations of the two dipterocarp species, Hopea odorata and Dryobalanops oblongifolia, and improved the performance of their seedlings when outplanted in the field plot. The growth of the species under high light level was greatly increased, but the concentration of foliar nutrients of the seedlings was correspondingly reduced. The order of performance in the field subplot categories was A&B>C>D&E and the order of foliar concentrations was D&E>C>A&B. The study of the effect of P fertiliser, light and types of soil on the growth was supplemented by nursery experiments using two dipterocarp species, Hopea odorata and Shorea acuminata. Soils from the plot and nursery soil as a control were used for potting the seedlings under two light levels, open (high) and shade (low). Adding P increased the infection of ectomycorrhizas (ECM) on the root tips and also increased the foliar P concentrations of Hopea odorata. Light appeared to reduce the infection of ECM. Experiments using sand cultures showed that P and Mg play an important role in influencing the growth of dipterocarp species. The growth of Hopea odorata significantly reduced when the concentrations of P was less than 2.07 mg 1.1 and when Mg was less than 3.63 mg 1-1 . The growth and the concentrations of foliar P and Mg of Hopea odorata were increased in response to an increase in external P and/or Mg supply. These results are interpreted as support for the hypothesis that P and maybe Mg availabilities would limit the establishment of the dipterocarp species. Based on these results, Hopea odorata is grouped as a light demanding species, Shorea acuminata is shade tolerant and Dryobalanops oblongifolia is intermediate species. Reforestation of the logged areas by means of enrichment planting with mixed species of different ecological requirements is one possible way of reclaiming the disturbed areas. Boosting P levels prior to planting may be an effective silvicultural approach in enrichment planting.
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Löf, Magnus. "Environmental stress on establishment and growth in Fagus sylvatica L. and Quercus robur L. seedlings /." Alnarp : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5625-8.pdf.
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Berry, Christopher J. J. "Post-dispersal seed predation in a conifer-broadleaf forest remnant : the importance of exotic mammals." Lincoln University, 2006. http://hdl.handle.net/10182/666.
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Despite extensive international acceptance of the critical role of mammalian post-dispersal seed predation in many plant communities, in New Zealand we have limited knowledge of these predators’ influence on plant recruitment in our forests. The principle objective of my thesis was to determine the importance of exotic mammals as post-dispersal seed predators in a New Zealand conifer-broadleaf forest remnant. To address this goal, I used a series of field-based experiments where the actions of different post-dispersal seed predators were separated by wire-mesh exclosures. My study was conducted at Mount Peel Forest Park Scenic Reserve, South Canterbury, New Zealand. Being a human modified conifer forest currently dominated by broadleaf species, it is typical of forest remnants in New Zealand. This presented an opportunity to study a wide range of both potential post-dispersal seed predators and broadleaf tree species. My findings indicate that exotic mammals are not only post-dispersal seed predators at Peel Forest, but are responsible for the majority of post-dispersal predation events observed. Ship rats (Rattus rattus) were the dominant post-dispersal seed predators, while brushtail possums (Trichosurus vulpecula), house mice (Mus musculus) and native invertebrates were also important post-dispersal seed predators for several tree species. Through use of time-lapse video and cafeteria experiments I found that exotic mammalian seed predators, when compared to native invertebrate seed predators, preyed upon larger-seeded plant species and were responsible for considerable seed losses of several tree species. However, exotic mammalian seed predators do share several foraging characteristics with native invertebrate seed predators, as predators foraged in similar habitats and responded in a similar way to changes in seed density. In investigating if post-dispersal seed predation by mammals had a flow-on effect to plant recruitment, I observed natural seedling densities at Peel Forest were significantly higher in the absence of mammalian seed predators, but I found no evidence that the presence of mammals significantly altered the overall species richness. At the community level, I did not find an interaction between habitat and exotic mammals, however I present evidence that for individual plant species a significant mammal : habitat interaction occurred. Consequently, even though my cafeteria experiment implied there was no significant difference in the overall amount of seed preyed upon within different habitats, the less favourable microsite conditions for germination under an intact continuous canopy allows mammals to exacerbate habitat-related patterns of seed mortality and have a noticeable effect on seedling establishment. In an effort to validate the use of manipulative experiments to predict the long-term effect of post-dispersal seed predation on plant dynamics, I attempted to link results of my cafeteria experiment with observed seedling abundance at Peel Forest. Seven tree species were used in this comparison and a strong correlation was observed. This result shows that the level of post-dispersal seed predation determined in the cafeteria experiment provided a good predictor of the effect of mammalian post-dispersal seed predation on seedling establishment. To fully gauge the impact of mammalian post-dispersal seed predators on seedling establishment, the relationship between these seed predators and the type of recruitment limitation experienced by a plant species was also investigated. By using a combination of seed addition, plot manipulations and seed predator exclusion I was able to investigate this relationship. I found evidence that seed limitation at Peel Forest is positively correlated with seed size, and that while mammalian post-dispersal seed predators can further reduce plant recruitment of plant species experiencing seed limitation, the influence of mammals in determining plant recruitment was limited for plant species experiencing microsite limitation. My study has proven that exotic mammals are now the dominant post-dispersal seed predators at Peel Forest, the amount of seed preyed upon varies among plant species, and post-dispersal seed predation by mammalian species can lead to differences in seedling richness and abundance. I proved that the influence of exotic mammals on seedling establishment is also linked to habitat structure and recruitment limitations. When combined these observations suggest that exotic mammalian post-dispersal seed predators may play an important role in determining landscape abundance and distribution of plants at Peel Forest.
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Ramachela, Khosi. "Studies on the mycorrhizosphere and nutrient dynamics in the establishment and growth of Uapaca kirkiana in Zimbabwe." Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019.1/1354.
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Thesis (PhD (Forest and Wood Science))—University of Stellenbosch, 2006.<br>Experiments carried out in this study sought to contribute to the understanding of the ecological interactions involved in Uapaca kirkiana seedling establishment and growth in a natural woodland ecosystem. These include soil pH reactions, plant root surface pH change, root exudates that affect the chemical behaviour of the soil in the vicinity of the root, and microbial effects. Although it was difficult to determine which of these factors play a dominant role in the soil-plant relationship, the study contributed to the understanding of the mycorrhizal fungi-host plant association. It revealed the diversity of mycorrhizal fungal species occurring in the different ecological sites, and also analysed the relationship between soil factors. Soil pH and K had significant influences on the fungi population diversity. K was considered important in its role in the translocation of auxins to the root sites where they enhance root susceptibility to mycorrhizal fungal infection. More work needs to be undertaken to establish the role of soil pH.
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Jackelman, James J. "Patterns of establishment of Acacia cyclops Cunn. ex G.Don seedlings in consolidated and unconsolidated coastal sands." Bachelor's thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/26716.
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