1,721,044 research outputs found
Seed Banks, Seed Mortality, and the Role of Fungal Communities in Neotropical Forests
No full textIndex words. Ascomycota; Cecropia; fungi; tropical forest ecology; seed bank; pioneer species; pathogens; ITS; Barro Colorado Island, Panama; La Selva, Costa Rica; Yasuni, Ecuador; recruitment limitation.Made available in DSpace on 2015-09-25T22:42:33Z (GMT). No. of bitstreams: 2
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Previous issue date: 2007Embargo set by: Seth Robbins for item 86651
Lift date: Forever
Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDsRestricted to the U of I community idenfinitely during batch ingest of legacy ETDsU of I Only128 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007
Plant-soil associations in a lower montane tropical forest: physiological acclimation and herbivore-mediated responses to nitrogen addition
No full textP>1. Soil nutrients influence plant productivity and community composition in tropical forests. In lower montane tropical forests in western Panama, the distribution of understory palm species over a scale of 1-20 km correlates with differences in soil nitrogen (N). We hypothesized that soil N determines seedling performance in the forest understory, and, may therefore influence species distributions along the soil N gradient. 2. We explored the potential for N availability to generate species-habitat associations through species-specific differences in biomass allocation, photosynthetic capacity, N use-efficiency, and susceptibility to herbivory. Seedlings of nine palm species from two sub-families and four habitat types were transplanted into N-addition and control plots at a low N site. Growth, mortality, biomass allocation, photosynthesis, foliar N content and herbivory were measured over 21 months. 3. Foliar N increased for all species (15-68%) following N addition. Most species showed strong (20-200%) increases in photosynthetic rates with N addition except two species with marginal decreases in photosynthetic rates (5-15%). However, shifts in physiological traits did not increase relative growth rate or change in biomass allocation for any species or N treatment combination. Rather, increased leaf quality contributed to greater levels of herbivory in species associated with soils of intermediate and high inorganic N availability. 4. Thus, potential increases in overall growth with N addition were masked by herbivory, resulting in no apparent growth response with increased N. We suggest that for understory palms, and potentially other montane forest plants, distribution patterns are driven by a combination of physiological and herbivore-mediated responses to soil nutrient availability
Resource partitioning of soil organic phosphorus: investigations from a tropical mountain forest
No full textOne of the major limitations of resource-niche theory to explain plant species diversity and distribution is the paucity of recognized resources. Recent investigations in grassland and tundra ecosystems indicate that plant species can specialize to exploit different forms of soil nitrogen. I hypothesized that a similar phenomena occurs in the tropics with soil phosphorus (P). I grew seedlings of arbuscular mycorrhizal (AM) Mollinedia darensi and Podocarpus olieofolius, ectomycorrhizal (EM) Oreomunnia mexicana, and nonmycorrhizal (NM) Roupala montana tree species in a hydroponic growth medium containing exclusively either inorganic, monoester, diester, inositol-P, or a no-P control. In addition, I assayed the production of P-mono and diesterase enzymes activity of each species to determine their capacity to remineralize P from organic sources. My results support the potential for resource partitioning to promote coexistence between mycorrhizal and nonmycorrhizal species. The mycorrhizal tree species exhibited similar growth, nutritional, and allocational responses across treatments, with growth and total P content high in inorganic-P and monoester-P and low in the inositol and diester-P treatments. When limited to inositol P, R. montana (NM) exhibited high growth, significantly greater total and specific leaf area, and significantly greater P use efficiency when compared to the other experimental treatments. R. montana (NM) also had 3 fold greater total P in the inositol P treatment than in the no-P control (p=0.064), and had significantly greater P-mono and diesterase activity than both AM and EM species. Together these results indicate that the potential exists for partitioning of soil P between mycorrhizal and NM plants, but not between AM and EM plants.Item withdrawn by Mark Zulauf ([email protected]) on 2011-07-19T18:26:40Z
Item was in collections:
University of Illinois Theses & Dissertations (ID: 1)
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The Role That Asexual Reproduction Plays in the Regeneration of Tropical Piper Shrubs: Habitat Differences and Genetic Consequences
No full text148 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.Asexual reproduction is a common, but little explored characteristic of many tropical plants with a variety of life-histories and habitat requirements. My dissertation research examined the ecological correlates and population genetic consequences of asexual reproductive success in five co-occurring Piper species using a combination of field experiments and molecular approaches. Working at the Barro Colorado Nature Monument (BCNM) Panama, I found that shade-tolerant species use asexual reproduction more often than do light-demanding species. Further, I showed that all Piper populations contain high genetic diversity regardless of the frequency of asexual reproduction in the population, and that these values of genetic diversity were higher than values found in most clonal plants in non-tropical ecosystems, but are similar to other clonal tropical plant species. Factors such as the accumulation of somatic mutations, habitat heterogeneity, and density dependent mortality, may be playing an important role in maintaining genetic diversity, despite high levels of asexual recruitment. I also integrated spatial geographic data with spatial genetic data and found that more than 50% of neighboring plants were close relatives and clones. I hypothesize that the strong spatial genetic structure found in this genus is the result of clumped dispersal of genetically related seeds and of a lack of overlap in the feeding territories of their seed dispersal agents, Carollia bats. Finally, one of the most striking findings of this research is that gene flow in these five Piper shrub species is generally more restricted than for tropical tree species. Limited gene flow, localized clonal spread and genetic drift could favor the establishment of small reproductively isolated populations, potentially leading to the speciation of some of the >1000 species of Piper currently present in the Tropics.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD
The Role That Asexual Reproduction Plays in the Regeneration of Tropical Piper Shrubs: Habitat Differences and Genetic Consequences
No full textAsexual reproduction is a common, but little explored characteristic of many tropical plants with a variety of life-histories and habitat requirements. My dissertation research examined the ecological correlates and population genetic consequences of asexual reproductive success in five co-occurring Piper species using a combination of field experiments and molecular approaches. Working at the Barro Colorado Nature Monument (BCNM) Panama, I found that shade-tolerant species use asexual reproduction more often than do light-demanding species. Further, I showed that all Piper populations contain high genetic diversity regardless of the frequency of asexual reproduction in the population, and that these values of genetic diversity were higher than values found in most clonal plants in non-tropical ecosystems, but are similar to other clonal tropical plant species. Factors such as the accumulation of somatic mutations, habitat heterogeneity, and density dependent mortality, may be playing an important role in maintaining genetic diversity, despite high levels of asexual recruitment. I also integrated spatial geographic data with spatial genetic data and found that more than 50% of neighboring plants were close relatives and clones. I hypothesize that the strong spatial genetic structure found in this genus is the result of clumped dispersal of genetically related seeds and of a lack of overlap in the feeding territories of their seed dispersal agents, Carollia bats. Finally, one of the most striking findings of this research is that gene flow in these five Piper shrub species is generally more restricted than for tropical tree species. Limited gene flow, localized clonal spread and genetic drift could favor the establishment of small reproductively isolated populations, potentially leading to the speciation of some of the >1000 species of Piper currently present in the Tropics.Made available in DSpace on 2015-09-28T15:22:06Z (GMT). No. of bitstreams: 2
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Previous issue date: 2007Embargo set by: Seth Robbins for item 88295
Lift date: Forever
Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDsRestricted to the U of I community idenfinitely during batch ingest of legacy ETDsU of I Only148 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007
The effect of soil nutrient availability on resource allocation in tropical tree species
Full text linkTropical tree communities are diverse in both their taxonomic composition and in their functional strategies for resource use and acquisition. Soil resources influence productivity of tropical forests and the distributions of tree species across edaphically heterogeneous landscapes. My dissertation evaluates functional variation among tropical trees in nutrient use, and the implications of this functional diversity of tropical forest nutrient and carbon cycling. Through a comparison forest litterfall patterns along a natural fertility gradient and experimental nutrient addition, I show that responses of forest productivity to nutrient availability are difficult to predict across space from environmental parameters alone due to turnover in forest functional composition. Evaluation of wood and foliar nutrient allocation along a soil fertility gradient demonstrates that tree species vary enormously both within and among soil habitats in the allocation of soil-derived nutrients to both foliar and woody biomass. I investigated the function of wood nitrogen and phosphorus repositories by conducting a sapling defoliation experiment, finding that wood P reserves are a dynamic pool reflecting both P in the soil and the demand for P allocation to leaves. Finally, I found that soil phosphorus availability is strongly correlated with the frequency of multiple stemmed trees across a regional forest plot network, indicating that reserves of soil derived nutrients influence the survival of trees after damage. By uncovering the importance of wood nutrient storage in forest ecosystem and community dynamics, this dissertation highlights a novel mechanism by which soil fertility influences the structure and function of tropical forests.Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2016-07-07 without embargo termsThe student, Katherine Heineman, accepted the attached license on 2016-04-19 at 15:34.The student, Katherine Heineman, submitted this Dissertation for approval on 2016-04-19 at 15:44.This Dissertation was approved for publication on 2016-04-21 at 11:53.DSpace SAF Submission Ingestion Package generated from Vireo submission #9348 on 2016-07-07 at 13:31:31Made available in DSpace on 2016-07-07T19:54:18Z (GMT). No. of bitstreams: 3
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Previous issue date: 2016-04-2
Diel patterns of insect herbivory and plant secondary metabolites in understory shrubs on Barro Colorado Island
Full text linkPlants produce a broad diversity of secondary metabolites as defenses against herbivory. In response, herbivorous insects have evolved a diversity of behavioral and biochemical counter-adaptations to these defenses. Despite that a significant portion of leaf area removal by insects in the tropics occurs at night, virtually all studies of chemically mediated interactions between herbivorous insects and their host plants have been conducted primarily or entirely during the daytime. Accordingly, I set out to quantify if rates of herbivory differ between the day and night. I used leaf photographs and single plant herbivore exclosures on 126 individual plants of four species in the genera Piper and Psychotria on Barro Colorado Island, Panama, to quantify the timing of herbivory over the course of 56 diel cycles. I found that on young leaves, protecting plants from herbivores during the night causes significantly fewer leaves to be damaged than if plants are protected only during the day but are exposed at night. I then characterized qualitative differences in the secondary metabolite profiles of the leaves of these plant species during daytime and nighttime hours using ultra high-performance liquid chromatography (UHPLC), electrospray ionization and molecular fragmentation, and tandem mass spectrometry (MS/MS). Network analyses show that plant secondary metabolites varied greatly in their presence in leaves over the course of several hours, suggesting that ecologically significant differences exist in the overall chemical profile that herbivores would encounter in leaves during different times of a day. Whether these variations in putative defense compounds may affect the foraging times and behaviors of herbivorous insects remains unresolved.
Most larval herbivores lack an effective means for dispersing to new hostplants. Therefore, feeding strategies that maximize assimilation and growth, and minimize time to pupation, are expected to be most advantageous. However, larval lepidopterans exhibit numerous behaviors that appear to interfere with maximizing the rate of foliage consumption. Caterpillars may limit their foraging times to specific periods of the diel due to uneven predation risk, to predictably variable abiotic (especially temperature and humidity) conditions, or to short-term variation in forage quality. While daily variation in forage nutrient levels and secondary metabolite concentrations has been well-studied in numerous systems, the influence of such variation on the daily rhythms of herbivore feeding activity has not yet been determined. I propose that the highly sensitive and specialized senses of olfaction and gustation in herbivores suit them well for limiting their feeding bouts to times of the day when plants are less well-defended (which I propose is the night). Such behavior is especially likely to occur in environments where there is relatively low variation between daytime and nighttime temperatures and humidity and where predation risk is always relatively high, or even higher during the nighttime than the day, as is likely the case in many tropical forests.Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2017-09-29 without embargo termsThe student, Luke Zehr, accepted the attached license on 2017-07-18 at 07:16.The student, Luke Zehr, submitted this Thesis for approval on 2017-07-18 at 07:28.This Thesis was approved for publication on 2017-07-20 at 10:00.DSpace SAF Submission Ingestion Package generated from Vireo submission #11506 on 2017-09-29 at 11:31:12Made available in DSpace on 2017-09-29T17:57:02Z (GMT). No. of bitstreams: 2
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Previous issue date: 2017-07-2
ppartition - Test for Associations between Plant Species and Soil Nutrients
No full text<p>Bundle of R functions used to analyze the associations between tree species and enzyme-labile soil phosphorus on a 50 ha forest plot on Barro Colorado Island in Panama. This package is supplement to the journal article 'Evidence for Soil Phosphorus Resource Partitioning in a Diverse Tropical Tree Community' by R. Müller, H. Elsenbeer and B. L. Turner.</p>
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Variation in Canopy Litterfall Along a Precipitation and Soil Fertility Gradient in a Panamanian Lower Montane Forest
No full textFertilization experiments in tropical forests have shown that litterfall increases in response to the addition of one or more soil nutrients. However, the relationship between soil nutrient availability and litterfall is poorly defined along natural soil fertility gradients, especially in tropical montane forests. Here, we measured litterfall for two years in five lower montane 1-ha plots spanning a soil fertility and precipitation gradient in lower montane forest at Fortuna, Panama. Litterfall was also measured in a concurrent nitrogen fertilization experiment at one site. Repeated-measures ANOVA was used to test for site (or treatment), year, and season effects on vegetative, reproductive and total litterfall. We predicted that total litterfall, and the ratio of reproductive to leaf litterfall, would increase with nutrient availability along the fertility gradient, and in response to nitrogen addition. We found that total annual litterfall varied substantially among 1-ha plots (4.78Mg/ha/yr to 7.96Mg/ha/yr), and all but the most aseasonal plot showed significant seasonality in litterfall. However, litterfall accumulation did not track soil nutrient availability; instead forest growing on relatively infertile soil, but dominated by an ectomycorrhizal tree species, had the highest total litterfall accumulation. In the fertilization plots, significantly more total litter fell in nitrogen addition relative to control plots, but this increase in response to nitrogen (13%) was small compared to variation observed among 1-ha plots. These results suggest that while litterfall at Fortuna is nutrient-limited, compositional and functional turnover along the fertility gradient obscure any direct relationship between soil resource availability and canopy productivity. Resumen Se demostro con experimentos de fertilizacion en bosques tropicales incrementos en la caida de hojarasca asociados con la adicion de nutrientes; empero, se desconoce la relacion entre la disponibilidad de nutrientes del suelo con la produccion de hojarasca en gradientes naturales de fertilidad del suelo, especialmente en bosques montanos tropicales. Medimos la produccion de hojarasca durante dos anos en cinco parcelas (1-ha) en bosques montanos bajos, sobre gradientes de fertilidad y precipitacion y en un experimento paralelo de fertilizacion de nitrogeno en la Reserva Forestal Fortuna, Panama. Predijimos incrementos de hojarasca total y reproductiva con la disponibilidad de nutrientes en el gradiente de fertilidad del suelo y en respuesta a la adicion de nitrogeno (13%). Encontramos que la hojarasca total varia sustancialmente entre parcelas (4.78 Mg/ha/yr hasta 7.96 Mg/ha/yr) y que en todas las parcelas, excepto la menos estacional, hay estacionalidad significativa en la cantidad de hojarasca; pero, la acumulacion de hojarasca no coincide con la disponibilidad de nutrientes en el suelo, porque el bosque sobre suelo poco fertil con dominio de una especie ectomicorricica, presento mayor acumulacion de hojarasca. Las parcelas con fertilizacion tenian significativamente mas hojarasca que las control; pero, el incremento en hojarasca en respuesta a la adicion de nitrogeno fue menor respecto a la variacion entre parcelas. Los resultados sugieren que mientras la produccion de hojarasca en Fortuna es limitada por nutrientes, la variacion en la composicion de especies a traves de gradientes de fertilidad ocultan cualquier relacion directa entre la disponibilidad de nutrientes del suelo y la productividad del dosel
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