Active Awards
COLLABORATIVE RESEARCH: UNDERSTANDING SPATIOTEMPORAL DYNAMICS OF PLANT-SOIL FEEDBACKS: CONSEQUENCES FOR SHRUB-GRASS INTERACTIONS IN A DRYLAND ECOTONE
NSF DEB (lead Y. Anny Chung, Univ Georgia, 2021 - 2025, $938,067)
Understanding the factors that allow species to move into new, more suitable habitats has become increasing urgent because of the rapid pace of human-caused environmental change. This project combines field and lab experiments with mathematical modeling to evaluate how plant-plant and plant-microbe interactions influence the movement of creosotebush, one of the most common and important plants of the warm deserts of North America (Sonoran, Chihuahuan and Mojave). Shrub encroachment is a global phenomenon expected to accelerate under future climates and elevated atmospheric CO2. The microbes that live in and on plants (microbiome) may play key, but as yet unappreciated, roles in the expansion of plants into new areas under climate and other environmental changes. To predict how these species interactions will drive or slow plant population expansion in future climates requires knowing the spatial extent and temporal speed at which these interactions occur, information that is currently lacking for many ecosystems. This project will enable forecasts of how plant-plant and plant-microbe interactions reshape the abundance and distributions of shrub and grass species at the limits of their geographic distributions, where the consequences of environmental change are likely to be most dramatic. Shrubland-grassland dynamics affect the amount of carbon stored by an ecosystem, drive rangeland management decisions, influence strategies to conserve biodiversity, and extend over 330 million hectares of North America alone. This project builds partnerships with stakeholders and managers to ensure knowledge transfer to benefit society. A science-art collaboration lies at the heart of the research activities, including the design and creation of 3D-printed plant models and artistic interpretations of plant morphologies that reach the general public through exhibition venues. The project will train at least three graduate students, one postdoctoral researcher, and several undergraduate researchers nurturing the next generation of thinkers in this field.
Understanding the factors that allow species to move into new, more suitable habitats has become increasing urgent because of the rapid pace of human-caused environmental change. This project combines field and lab experiments with mathematical modeling to evaluate how plant-plant and plant-microbe interactions influence the movement of creosotebush, one of the most common and important plants of the warm deserts of North America (Sonoran, Chihuahuan and Mojave). Shrub encroachment is a global phenomenon expected to accelerate under future climates and elevated atmospheric CO2. The microbes that live in and on plants (microbiome) may play key, but as yet unappreciated, roles in the expansion of plants into new areas under climate and other environmental changes. To predict how these species interactions will drive or slow plant population expansion in future climates requires knowing the spatial extent and temporal speed at which these interactions occur, information that is currently lacking for many ecosystems. This project will enable forecasts of how plant-plant and plant-microbe interactions reshape the abundance and distributions of shrub and grass species at the limits of their geographic distributions, where the consequences of environmental change are likely to be most dramatic. Shrubland-grassland dynamics affect the amount of carbon stored by an ecosystem, drive rangeland management decisions, influence strategies to conserve biodiversity, and extend over 330 million hectares of North America alone. This project builds partnerships with stakeholders and managers to ensure knowledge transfer to benefit society. A science-art collaboration lies at the heart of the research activities, including the design and creation of 3D-printed plant models and artistic interpretations of plant morphologies that reach the general public through exhibition venues. The project will train at least three graduate students, one postdoctoral researcher, and several undergraduate researchers nurturing the next generation of thinkers in this field.
QUANTIFYING THE MICROBIAL CONTRIBUTION TO COMMUNITY RECOVERY FROM DROUGHT
NSF 1911451 (to J. Rudgers et al.; 2019-2023; $1,009,923)
Understanding how ecological communities recover from extreme weather events can improve our ability to manage and enhance their productivity and services. Extreme droughts are predicted to increase in many regions, and may be critically important in arid and semi-arid drylands, which are often more sensitive to drought than wetter ecosystems. This project leverages previously NSF-funded infrastructure for creating experimental drought in dry grasslands in order to determine how much soil microbes aid in the recovery from extreme drought. Prior research has uncovered two key results that have yet to be united in contemporary research. First, drought leaves a legacy in the soil by changing the composition of microbes; this legacy can persist long after drought has ended. Second, additions of microbes can speed community recovery after disturbance. Combined, these two results suggest that soil microbes could drive the pace of ecological recovery from drought, but experimental studies are needed. This project will use microbial experiments in the field and greenhouse to determine the magnitude of drought impacts on drylands and elucidate how much soil microbes matter to recovery and resilience. This project trains the next-generation of diverse scientists by supporting a female Hispanic postdoctoral researcher, two female graduate students (one Hispanic), and independent research experiences for undergraduates, including partnership with the Southwestern Indian Polytechnic Institute. A new inquiry-based laboratory module reaches biology majors at a Hispanic-serving institution, and a drought-focused K-12 unit enhances next-generation science standards. The project has global importance because drylands occupy a large (~45%) and rapidly expanding percentage of land area and contribute greatly to global carbon fluctuations. Nearly 40% of people live in the world's drylands, and improved understanding of the processes by which drylands recover from drought may enable rapid restoration via microbial amendments, delivering new land management strategies.
Understanding how ecological communities recover from extreme weather events can improve our ability to manage and enhance their productivity and services. Extreme droughts are predicted to increase in many regions, and may be critically important in arid and semi-arid drylands, which are often more sensitive to drought than wetter ecosystems. This project leverages previously NSF-funded infrastructure for creating experimental drought in dry grasslands in order to determine how much soil microbes aid in the recovery from extreme drought. Prior research has uncovered two key results that have yet to be united in contemporary research. First, drought leaves a legacy in the soil by changing the composition of microbes; this legacy can persist long after drought has ended. Second, additions of microbes can speed community recovery after disturbance. Combined, these two results suggest that soil microbes could drive the pace of ecological recovery from drought, but experimental studies are needed. This project will use microbial experiments in the field and greenhouse to determine the magnitude of drought impacts on drylands and elucidate how much soil microbes matter to recovery and resilience. This project trains the next-generation of diverse scientists by supporting a female Hispanic postdoctoral researcher, two female graduate students (one Hispanic), and independent research experiences for undergraduates, including partnership with the Southwestern Indian Polytechnic Institute. A new inquiry-based laboratory module reaches biology majors at a Hispanic-serving institution, and a drought-focused K-12 unit enhances next-generation science standards. The project has global importance because drylands occupy a large (~45%) and rapidly expanding percentage of land area and contribute greatly to global carbon fluctuations. Nearly 40% of people live in the world's drylands, and improved understanding of the processes by which drylands recover from drought may enable rapid restoration via microbial amendments, delivering new land management strategies.
LTREB: Community reordering alters ecosystem processes in desert grassland
NSF 1856383 (to S. Collins, co-PI J. Rudgers; 2019-2023; $489,000)
Global environmental change can cause large-scale disruptions to ecosystems by gradually shifting both the presence and abundance of different plant species. Many ecosytems are characterized by a few dominant plants, but it is unclear if these species will remain dominants as environmental conditions change. The loss of dominant species may have a large impact, creating a potential cascade of effects on the overall structure and function of the ecosystem. Ongoing work at the Sevilleta National Wildlife Refuge in New Mexico indicates that a common desert grass is gradually replacing a widespread Great Plains grass. To understand how changes in rainfall amount, timing and variability affect the rate, amount and direction of reordering among the dominant grass species, this project will link the effects of species reordering to carbon cycling and net primary production. Experiments will alter water, temperature and nitrogen availability to test how grasslands respond to these environmental changes. Dryland ecosystems, which cover ~45% of global continental land area, have measurable impacts on the global carbon budget. Drylands are changing rapidly in response to droughts, air pollution, and increased rainfall variability. Community reordering may be key to advancing the understanding of different global change factors affecting dryland ecosystems in the southwestern United States and elsewhere.
Global environmental change can cause large-scale disruptions to ecosystems by gradually shifting both the presence and abundance of different plant species. Many ecosytems are characterized by a few dominant plants, but it is unclear if these species will remain dominants as environmental conditions change. The loss of dominant species may have a large impact, creating a potential cascade of effects on the overall structure and function of the ecosystem. Ongoing work at the Sevilleta National Wildlife Refuge in New Mexico indicates that a common desert grass is gradually replacing a widespread Great Plains grass. To understand how changes in rainfall amount, timing and variability affect the rate, amount and direction of reordering among the dominant grass species, this project will link the effects of species reordering to carbon cycling and net primary production. Experiments will alter water, temperature and nitrogen availability to test how grasslands respond to these environmental changes. Dryland ecosystems, which cover ~45% of global continental land area, have measurable impacts on the global carbon budget. Drylands are changing rapidly in response to droughts, air pollution, and increased rainfall variability. Community reordering may be key to advancing the understanding of different global change factors affecting dryland ecosystems in the southwestern United States and elsewhere.
LTER: Sevilleta (SEV) Site: Climate variability at dryland ecotones
NSF 1655499 (to J. Rudgers et. al; 2018-2023; $6,432,997)
Arid areas, which already comprise more than 40% of land on earth, are expanding in many places. Yearly differences in climate greatly affect the ecology and evolution of plants and animals in these drylands. The Sevilleta Long-Term Ecological Research (LTER) site in New Mexico includes five major dryland habitats or ecosystems. This research will expand ecological knowledge of those ecosystems. The guiding question is: How do long-term climate trends drive what happens in dryland ecosystems? In particular, how does one type of dryland ecosystem get turned into another type? Scientists will develop new theory to predict what happens when, for example, it rains less. They will collect the long-term data needed to test their ideas. They will also do experiments that change patterns of rainfall. This project will allow scientists to improve forecasts for drylands, transforming our understanding of these ecosystems worldwide. Scientists at Sevilleta will recruit and train a diverse workforce through activities at all levels of learning. These include many schoolyard lessons, undergraduate research programs, and interdisciplinary graduate and professional training. Societal impacts of the program include strong collaborations with local, regional, and national land managers.
Arid areas, which already comprise more than 40% of land on earth, are expanding in many places. Yearly differences in climate greatly affect the ecology and evolution of plants and animals in these drylands. The Sevilleta Long-Term Ecological Research (LTER) site in New Mexico includes five major dryland habitats or ecosystems. This research will expand ecological knowledge of those ecosystems. The guiding question is: How do long-term climate trends drive what happens in dryland ecosystems? In particular, how does one type of dryland ecosystem get turned into another type? Scientists will develop new theory to predict what happens when, for example, it rains less. They will collect the long-term data needed to test their ideas. They will also do experiments that change patterns of rainfall. This project will allow scientists to improve forecasts for drylands, transforming our understanding of these ecosystems worldwide. Scientists at Sevilleta will recruit and train a diverse workforce through activities at all levels of learning. These include many schoolyard lessons, undergraduate research programs, and interdisciplinary graduate and professional training. Societal impacts of the program include strong collaborations with local, regional, and national land managers.
Host-microbe symbiosis through the lens of stochastic demography
NSF 1754433 (to T.E.X. Miller, J. Rudgers, K. Whitney; 2018-2023, Total Award $482,500 UNM Award $178,630)
Nearly all plants and animals harbor microbes such as bacteria that live on or in them. Understanding the influence of these microscopic organisms on their host species may advance our ability to solve problems in agriculture, wildlife disease, and human health. Before these applications can be fully realized, biologists first require a better understanding of when and how microbes influence the fitness of their host. This project will test the hypothesis that the effects of microbes on their hosts fluctuate from year to year, being beneficial in stressful years (when hosts need assistance) but neutral or costly in favorable years. As a consequence, hosts with microbes may experience reduced year-to-year fluctuation in fitness compared to hosts without microbes, which may be an important benefit of harboring microbes. This hypothesis will be tested by extending data collection of a long-term field experiment with grass species that harbor fungal microbes, collecting new data on the genetics of the grasses in that experiment, an applying a statistical modeling approach. Fungal microbes that live inside plants are a widespread in grasses, including forage grasses that are important to livestock, and this research could have important agricultural applications. Additionally, this project will provide research training for students at the high school, undergraduate, and graduate levels.
Nearly all plants and animals harbor microbes such as bacteria that live on or in them. Understanding the influence of these microscopic organisms on their host species may advance our ability to solve problems in agriculture, wildlife disease, and human health. Before these applications can be fully realized, biologists first require a better understanding of when and how microbes influence the fitness of their host. This project will test the hypothesis that the effects of microbes on their hosts fluctuate from year to year, being beneficial in stressful years (when hosts need assistance) but neutral or costly in favorable years. As a consequence, hosts with microbes may experience reduced year-to-year fluctuation in fitness compared to hosts without microbes, which may be an important benefit of harboring microbes. This hypothesis will be tested by extending data collection of a long-term field experiment with grass species that harbor fungal microbes, collecting new data on the genetics of the grasses in that experiment, an applying a statistical modeling approach. Fungal microbes that live inside plants are a widespread in grasses, including forage grasses that are important to livestock, and this research could have important agricultural applications. Additionally, this project will provide research training for students at the high school, undergraduate, and graduate levels.
Past Awards
THE POTENTIAL FOR CLIMATE INDUCED DISRUPTION OF PLANT-MICROBE SYMBIOSEs
NSF 1354972 (to J. Rudgers et al.; 2014 - 2018; $829,238)
Species are moving up mountainsides as temperatures rise. As species move, important interactions between species may be disrupted, with as yet unknown consequences. The coupled dynamics arising from species interactions can produce complex and unanticipated ecological responses to climate change. Novel species responses may feedback on the rate of climate change itself by altering processes that influence carbon cycling. Fungal symbionts of plants, such as endophytes and mycorrhizal fungi, are now well documented to influence the resilience of plants to climate change. Fungi also play critical roles in carbon cycling, by storing carbon in recalcitrant forms and decomposing organic material. Therefore, the potential for climate change to decouple plant and fungal interactions deserves careful attention. While plant movement under changing climates is easily observed, movement of fungal species is inconspicuous and little studied. This project will gauge the potential for plant-fungal symbioses to become destabilized under future climates and test the consequences of disruptions for individual plant species and carbon cycling. First, the distributions of fungal symbionts colonizing plant leaves and roots will be described along replicated elevation gradients in the Rocky Mountains of Colorado, using microscopy and DNA sequencing. This work constitutes the largest altitudinal survey of fungal symbionts anywhere in the world. Second, an NSF-funded, 22-year long warming experiment will be leveraged to test, for the first time, whether fungal responses to climate warming match their distributional patterns along natural, altitudinal gradients. Third, reciprocal transplants of plants and fungi will mimic range shifts under a 3 degree celsius warmer climate and experimentally test the consequences of symbiosis decoupling. Fourth, functional assays will evaluate how disrupted symbioses affect carbon cycling.
Species are moving up mountainsides as temperatures rise. As species move, important interactions between species may be disrupted, with as yet unknown consequences. The coupled dynamics arising from species interactions can produce complex and unanticipated ecological responses to climate change. Novel species responses may feedback on the rate of climate change itself by altering processes that influence carbon cycling. Fungal symbionts of plants, such as endophytes and mycorrhizal fungi, are now well documented to influence the resilience of plants to climate change. Fungi also play critical roles in carbon cycling, by storing carbon in recalcitrant forms and decomposing organic material. Therefore, the potential for climate change to decouple plant and fungal interactions deserves careful attention. While plant movement under changing climates is easily observed, movement of fungal species is inconspicuous and little studied. This project will gauge the potential for plant-fungal symbioses to become destabilized under future climates and test the consequences of disruptions for individual plant species and carbon cycling. First, the distributions of fungal symbionts colonizing plant leaves and roots will be described along replicated elevation gradients in the Rocky Mountains of Colorado, using microscopy and DNA sequencing. This work constitutes the largest altitudinal survey of fungal symbionts anywhere in the world. Second, an NSF-funded, 22-year long warming experiment will be leveraged to test, for the first time, whether fungal responses to climate warming match their distributional patterns along natural, altitudinal gradients. Third, reciprocal transplants of plants and fungi will mimic range shifts under a 3 degree celsius warmer climate and experimentally test the consequences of symbiosis decoupling. Fourth, functional assays will evaluate how disrupted symbioses affect carbon cycling.
ECOLOGICAL DYNAMICS OF VERTICALLY TRANSMITTED SYMBIONTS IN HOSTS WITH COMPLEX LIFE HISTORIES
NSF 1145588 (to T.E.X. Miller and J. Rudgers; 2012 - 2017; $560,000)
Many plants and animals harbor microbial symbionts, i.e., microbes that live on or in individuals of a host species, which are transmitted from host parent to offspring. However, there is striking variation in the frequency of microbial symbiosis across host species and even among populations of the same species. In some cases, a microbial symbiont species is present in all individuals of a host species, leading to tight integration of the ecology and evolution of host and symbiont. In other cases, such as fungal symbionts living within plants, the symbiont occurs at intermediate frequencies, with symbiotic and symbiont-free individuals co-occurring within host populations. This project will address the question of why there is wide variation in the frequency of host-symbiont associations. Given the strong evolutionary and ecological impacts of microbial symbionts, answering this question is a major challenge in biology. This project will test the hypothesis that the life history traits of the host species can explain much of the observed variation in symbiosis. Theory suggests that the population dynamics of symbionts are determined by how they affect the fitness of their host and the efficiency of their transmission among individual hosts. Host species with more complex life histories (longer lifespan, repeated reproduction, different stages of development) have more opportunities to be affected by symbionts and to lose them. This project will develop new mathematical models to examine the influence of host life history traits on symbiont population dynamics, and use field experiments to test model predictions. Experimental work will focus on the well-studied model system of grasses and their fungal symbionts. Symbiont dynamics in annual host grasses will be compared to dynamics in perennial host grasses that have more complex life histories. The integration of theoretical and field-based research is expected to provide a transformative approach to understanding and predicting the dynamics of symbionts.
Many plants and animals harbor microbial symbionts, i.e., microbes that live on or in individuals of a host species, which are transmitted from host parent to offspring. However, there is striking variation in the frequency of microbial symbiosis across host species and even among populations of the same species. In some cases, a microbial symbiont species is present in all individuals of a host species, leading to tight integration of the ecology and evolution of host and symbiont. In other cases, such as fungal symbionts living within plants, the symbiont occurs at intermediate frequencies, with symbiotic and symbiont-free individuals co-occurring within host populations. This project will address the question of why there is wide variation in the frequency of host-symbiont associations. Given the strong evolutionary and ecological impacts of microbial symbionts, answering this question is a major challenge in biology. This project will test the hypothesis that the life history traits of the host species can explain much of the observed variation in symbiosis. Theory suggests that the population dynamics of symbionts are determined by how they affect the fitness of their host and the efficiency of their transmission among individual hosts. Host species with more complex life histories (longer lifespan, repeated reproduction, different stages of development) have more opportunities to be affected by symbionts and to lose them. This project will develop new mathematical models to examine the influence of host life history traits on symbiont population dynamics, and use field experiments to test model predictions. Experimental work will focus on the well-studied model system of grasses and their fungal symbionts. Symbiont dynamics in annual host grasses will be compared to dynamics in perennial host grasses that have more complex life histories. The integration of theoretical and field-based research is expected to provide a transformative approach to understanding and predicting the dynamics of symbionts.
DO SYMBIOSES DETERMINE PLANT SPECIES ABUNDANCES? HOW ENDOPHYTIC FUNGI MAY CONTROL RARITY, DOMINANCE, AND INVASIVENESS OF GRASSES
NSF 054278 (to J. Rudgers; 4/2006 - 4/2011; $449,946)
Species fundamentally vary in their abundance, spanning a range from federally endangered species to severely weedy invaders. Several hypotheses have been proposed to explain this pattern, but none sufficiently account for observed variation. In part, this failure might reflect the fact that microbial symbioses (widespread, mutually beneficial associations between microbes and plants) have been largely ignored. This proposal forges a new direction by evaluating the role of microbial symbioses in governing rarity and invasiveness. Taking advantage of the experimentally tractable symbioses between grasses and microbial endophytes (fungi that live within plant leaves), proposed experiments and demographic models test whether and how symbionts increase host abundance. In grasses, endophytes may improve host resistance to herbivory through the production of alkaloids toxic to insects and mammals and also may enhance host drought tolerance. Comparative experiments on paired rare and common grass species will test predictions that symbionts' benefits are greater for common than rare host species and differ between native and non-native hosts, providing the most comprehensive study to date on the ecology of grass-endophyte symbioses. A clearer understanding of endophyte ecology can offer novel strategies for rare plant conservation and invasive plant control (e.g., via endophyte additions or eliminations). Through networks established in both Indiana and Texas, information will be broadly communicated to state agencies, preserve managers, seed companies, and conservation organizations. The work will additionally integrate teaching and research, by training graduate and undergraduate students as well as bringing contemporary research into the classroom.
Species fundamentally vary in their abundance, spanning a range from federally endangered species to severely weedy invaders. Several hypotheses have been proposed to explain this pattern, but none sufficiently account for observed variation. In part, this failure might reflect the fact that microbial symbioses (widespread, mutually beneficial associations between microbes and plants) have been largely ignored. This proposal forges a new direction by evaluating the role of microbial symbioses in governing rarity and invasiveness. Taking advantage of the experimentally tractable symbioses between grasses and microbial endophytes (fungi that live within plant leaves), proposed experiments and demographic models test whether and how symbionts increase host abundance. In grasses, endophytes may improve host resistance to herbivory through the production of alkaloids toxic to insects and mammals and also may enhance host drought tolerance. Comparative experiments on paired rare and common grass species will test predictions that symbionts' benefits are greater for common than rare host species and differ between native and non-native hosts, providing the most comprehensive study to date on the ecology of grass-endophyte symbioses. A clearer understanding of endophyte ecology can offer novel strategies for rare plant conservation and invasive plant control (e.g., via endophyte additions or eliminations). Through networks established in both Indiana and Texas, information will be broadly communicated to state agencies, preserve managers, seed companies, and conservation organizations. The work will additionally integrate teaching and research, by training graduate and undergraduate students as well as bringing contemporary research into the classroom.
CAN MICROBIAL SYMBIOSIS MEDIATE EFFECTS OF CLIMATE CHANGE ON THE FUNCTIONING OF AN ECOSYSTEM ENGINEER?
NSF 0918267 (to J. Rudgers; 9/2009 - 8/2012; $62,362)
Accurate predictions of community and ecosystem responses to climate change will require identifying not only the direct effects of altered climate on species, but also the indirect effects that occur through biotic interactions or as a result of species impacts on the environment. Those indirect effects may be particularly important for species that modify physical habitat structure. For plants, microbial symbionts have strong potential to mediate plant responses to climate change. This project will compare the relative importance of abiotic and biotic controls on the ways that Ammophila breviligulata (American beach grass) modifies its environment in Great Lakes dune systems. Ammophila breviligulata stabilizes moving sand through prolific root production during the early stages of dune succession, and thus is considered an important ecosystem engineer. Increased summer droughts resulting from climate change may reduce the capacity of A. breviligulata to bind sand and stabilize dunes. However, A. breviligulata hosts a symbiotic fungal endophyte in its leaves and arbuscular mycorrhizal fungi in its roots, which may improve tolerance to drought, alter root architecture, and thus enhance soil stability. Using a combination of lab and field experiments and broad geographic surveys, this study will test whether a microbial symbiosis can mediate effects of climate change on the functioning of an ecosystem engineer. This work will increase knowledge of non-agronomic plant symbionts, with direct application for improving dune restorations in the Great Lakes and Atlantic Coast, as well as for managing invasive populations of A. breviligulata on the West Coast. Underrepresented minorities will be recruited through the NSF AGEP program, providing research experiences for economically disadvantaged students in an EPSCoR state. K-12 education will also be enhanced by providing high school student research opportunities and a national teacher workshop.
Accurate predictions of community and ecosystem responses to climate change will require identifying not only the direct effects of altered climate on species, but also the indirect effects that occur through biotic interactions or as a result of species impacts on the environment. Those indirect effects may be particularly important for species that modify physical habitat structure. For plants, microbial symbionts have strong potential to mediate plant responses to climate change. This project will compare the relative importance of abiotic and biotic controls on the ways that Ammophila breviligulata (American beach grass) modifies its environment in Great Lakes dune systems. Ammophila breviligulata stabilizes moving sand through prolific root production during the early stages of dune succession, and thus is considered an important ecosystem engineer. Increased summer droughts resulting from climate change may reduce the capacity of A. breviligulata to bind sand and stabilize dunes. However, A. breviligulata hosts a symbiotic fungal endophyte in its leaves and arbuscular mycorrhizal fungi in its roots, which may improve tolerance to drought, alter root architecture, and thus enhance soil stability. Using a combination of lab and field experiments and broad geographic surveys, this study will test whether a microbial symbiosis can mediate effects of climate change on the functioning of an ecosystem engineer. This work will increase knowledge of non-agronomic plant symbionts, with direct application for improving dune restorations in the Great Lakes and Atlantic Coast, as well as for managing invasive populations of A. breviligulata on the West Coast. Underrepresented minorities will be recruited through the NSF AGEP program, providing research experiences for economically disadvantaged students in an EPSCoR state. K-12 education will also be enhanced by providing high school student research opportunities and a national teacher workshop.
LINKING MICROBIAL COMMUNITY COMPOSITION TO THE ECOLOGICAL DOMINANCE OF PLANTS
NSF 0949719 (to V. Huguet, co-PI J. Rudgers; 6/2010 - 5/2012; $271,854)
Plant species abundance is an essential component of ecosystem biodiversity and function, but understanding what factors regulate rarity and commonness has been elusive. Numerous studies have compared traits that might distinguish between rare and common species (e.g. seed size) and tested factors potentially contributing to rarity (e.g. competition), but these efforts have not substantially explained observed variation in plant abundances. The proposed research will test the novel hypothesis that soil microorganisms, often overlooked by community ecologists, may explain rarity in plants through soil community feedbacks. In the feedback process, a plant species alters the composition of the soil microbial community, and the altered soil community then affects plant performance relative to other plants in the community. Negative feedback should drive plants toward rarity, whereas positive feedback should promote plant dominance. If feedback regulates plant rarity, then rare and common plant species should either support different soil microbial communities or respond differently to the same community. This prediction has not been tested. A field survey will be conducted to determine whether co-occurring rare and common grass species develop consistently different microbial communities in nature. The potential function of these microorganisms will also be compared by measuring activities for enzymes involved in carbon, nitrogen and phosphorous cycles. Then, using a reciprocal soil transfer experiment in the greenhouse (i.e. rare plants will be grown on common plants' soil and vice-versa), the second part of this study will test if rare plants experience more negative feedbacks than common ones. A fractionation experiment in which plants interact with different components of the microbial community (e.g. all microbes or bacteria only or fungi only) will help understand which microbes are more actively driving soil community feedbacks. The data generated have high potential to transform current understanding of the factors governing plant species abundance. Results will be disseminated to policy-makers and land managers through existing collaborations with the Nature Conservancy, US Forest Service, National Parks, and private seed companies. The research will integrate teaching and research by building partnerships with K-12 educators, by funding a female post-doc, and by training graduate and undergraduate students from diverse backgrounds.
Plant species abundance is an essential component of ecosystem biodiversity and function, but understanding what factors regulate rarity and commonness has been elusive. Numerous studies have compared traits that might distinguish between rare and common species (e.g. seed size) and tested factors potentially contributing to rarity (e.g. competition), but these efforts have not substantially explained observed variation in plant abundances. The proposed research will test the novel hypothesis that soil microorganisms, often overlooked by community ecologists, may explain rarity in plants through soil community feedbacks. In the feedback process, a plant species alters the composition of the soil microbial community, and the altered soil community then affects plant performance relative to other plants in the community. Negative feedback should drive plants toward rarity, whereas positive feedback should promote plant dominance. If feedback regulates plant rarity, then rare and common plant species should either support different soil microbial communities or respond differently to the same community. This prediction has not been tested. A field survey will be conducted to determine whether co-occurring rare and common grass species develop consistently different microbial communities in nature. The potential function of these microorganisms will also be compared by measuring activities for enzymes involved in carbon, nitrogen and phosphorous cycles. Then, using a reciprocal soil transfer experiment in the greenhouse (i.e. rare plants will be grown on common plants' soil and vice-versa), the second part of this study will test if rare plants experience more negative feedbacks than common ones. A fractionation experiment in which plants interact with different components of the microbial community (e.g. all microbes or bacteria only or fungi only) will help understand which microbes are more actively driving soil community feedbacks. The data generated have high potential to transform current understanding of the factors governing plant species abundance. Results will be disseminated to policy-makers and land managers through existing collaborations with the Nature Conservancy, US Forest Service, National Parks, and private seed companies. The research will integrate teaching and research by building partnerships with K-12 educators, by funding a female post-doc, and by training graduate and undergraduate students from diverse backgrounds.
YELLOW CRAZY ANT INVASION OF THE SAMOAN ARCHIPELAGO: DO NOVEL MUTUALISMS AMPLIFY THE ECOLOGICAL IMPACTS?
National Geographic Society 8237-07 (to A. Savage, J. Rudgers, and K. Whitney; 5/2007-9/2008; $20,000)
Invasive species pose one of the greatest threats to global biodiversity, and tropical oceanic islands are particularly vulnerable to their negative impacts. For these systems, invasion by the yellow crazy ant (Anoplolepis gracilipes) is a major threat. Identified by the International Conservation Union as one of the world's 100 worst invaders, this species has already decimated some tropical island ecosystems. In Samoa, an island group integral to the Polynesia/Micronesia biodiversity hotspot, presence of the yellow crazy ant is of acute concern. Our data suggest that yellow crazy ants are at a critical stage in their invasion, possibly transitioning from low-level persistence into a phase of rapid population growth with potentially severe ecological consequences. We will investigate the ecological mechanisms that underlie yellow crazy ant success, examine early impacts of the invasion on native communities, and test how community dynamics, specifically novel beneficial relationships with native species, may feed back to influence the invasion. This work will both advance ecological theory and provide critical information needed for conservation planning.
Invasive species pose one of the greatest threats to global biodiversity, and tropical oceanic islands are particularly vulnerable to their negative impacts. For these systems, invasion by the yellow crazy ant (Anoplolepis gracilipes) is a major threat. Identified by the International Conservation Union as one of the world's 100 worst invaders, this species has already decimated some tropical island ecosystems. In Samoa, an island group integral to the Polynesia/Micronesia biodiversity hotspot, presence of the yellow crazy ant is of acute concern. Our data suggest that yellow crazy ants are at a critical stage in their invasion, possibly transitioning from low-level persistence into a phase of rapid population growth with potentially severe ecological consequences. We will investigate the ecological mechanisms that underlie yellow crazy ant success, examine early impacts of the invasion on native communities, and test how community dynamics, specifically novel beneficial relationships with native species, may feed back to influence the invasion. This work will both advance ecological theory and provide critical information needed for conservation planning.
DISSERTATION RESEARCH: CONSEQUENCES OF PLANT SPECIES AND GENETIC DIVERSITY FOR MICROBIAL COMMUNITY COMPOSITION AND FUNCTION.
NSF 0910268 (to J. Rudgers, co-PI K. Crawford; 7/2009 - 9/2011; $14,572)
Soil microbes are vitally important to ecosystem function. Bacteria and fungi decompose dead plant and animal matter and make the nutrients contained within them available for plants to use for growth and other functions; the living plant material is then available for consumption by other organisms. Despite their ecological value and ubiquity, little is known about how soil microbial communities are affected by the diversity of the plant communities with which they co-exist. Individual plant species cultivate different microbial communities, and recent work is showing that the genetic identity of the plant, as well as the species identity, may affect its associated microbes. Using constructed sand dune plant communities in Michigan that mimic levels of species diversity and genetic diversity found in nature, this study is one of the first to address how plant species diversity and genetic diversity influence microbial community structure and function. The microbial community will be characterized using several techniques, providing detailed information on the diversity of microbes present as well as their roles in the environment. Establishing linkages between plant and microbial diversity will illuminate this potential avenue for plants to influence ecosystem function via soils. Results from this study will provide valuable information to conservationists and restoration ecologists by elucidating the relative roles of multiples levels of diversity for ecosystem function. Furthermore, this project will help restore a critically endangered ecosystem (freshwater sand dunes) and provide information on optimal restoration practices. Results will be widely distributed to conservation groups, including the Alliance for the Great Lakes, the Nature Conservancy, and the Friends of Sleeping Bear Dunes, and government agencies, including the National Park Service and the Environmental Protection Agency. This research also offers several opportunities for undergraduate students interested in field ecology.
Soil microbes are vitally important to ecosystem function. Bacteria and fungi decompose dead plant and animal matter and make the nutrients contained within them available for plants to use for growth and other functions; the living plant material is then available for consumption by other organisms. Despite their ecological value and ubiquity, little is known about how soil microbial communities are affected by the diversity of the plant communities with which they co-exist. Individual plant species cultivate different microbial communities, and recent work is showing that the genetic identity of the plant, as well as the species identity, may affect its associated microbes. Using constructed sand dune plant communities in Michigan that mimic levels of species diversity and genetic diversity found in nature, this study is one of the first to address how plant species diversity and genetic diversity influence microbial community structure and function. The microbial community will be characterized using several techniques, providing detailed information on the diversity of microbes present as well as their roles in the environment. Establishing linkages between plant and microbial diversity will illuminate this potential avenue for plants to influence ecosystem function via soils. Results from this study will provide valuable information to conservationists and restoration ecologists by elucidating the relative roles of multiples levels of diversity for ecosystem function. Furthermore, this project will help restore a critically endangered ecosystem (freshwater sand dunes) and provide information on optimal restoration practices. Results will be widely distributed to conservation groups, including the Alliance for the Great Lakes, the Nature Conservancy, and the Friends of Sleeping Bear Dunes, and government agencies, including the National Park Service and the Environmental Protection Agency. This research also offers several opportunities for undergraduate students interested in field ecology.
PARSING THE EFFECTS OF HOST SPECIFICITY AND GEOGRAPHY ON PLANT-FUNGAL SYMBIOSES UNDER CLIMATE CHANGE
NSF 1456955 (to J. Rudgers et al.; 2015-2020; Total Award $1,089,147 UNM Award $406,134)
Climate models project higher temperatures, more variability in precipitation, and more extreme weather events in the future. Under such changing environments, foundation plant species, which promote stable conditions for other species and support fundamental ecosystem processes, may benefit from microbial partners that enhance plant survival during climate extremes. However, whether microbial partners can help to buffer ecosystems against climate change remains unknown. This research investigates a widespread, but poorly known, group of fungi that commonly grow in the roots of dominant forage grasses. The project determines how the benefits of these fungi vary along gradients of drought and heat stress, differ among grass species, and shift across geographic regions -- from the deserts of New Mexico to the tallgrass prairies of eastern Kansas. By filling these key knowledge gaps, this work has high promise for identifying fungi that help plants survive and grow in stressful climates. Deeper insight into the biology of root endophytes has the potential to transform understanding of how plants respond to drought and heat in the same way that studies on mycorrhizal fungi overturned paradigms about how plants acquire nutrients. This project tests whether root-associated fungi moderate the loss of net primary production during droughts and heat waves by benefiting grass species that dominate grasslands. The work addresses the following questions: (1) What is the relative importance of host species identity versus geographic/climatic gradients in explaining variation in symbiont abundance and composition? (2) How strongly do host species identity and geographic origin influence the magnitude of symbiont benefits across gradients of heat and drought stress? (3) Can symbiont-mediated amelioration of stress be generalized from laboratory settings to predict outcomes in the field? Activities include field surveys along latitudinal gradients, next-generation high-throughput sequencing of root fungi, development of a large fungal culture collection, multi-factor greenhouse trials that manipulate drought and heat, and field tests that leverage existing, large, cross-site rainfall experiment.
Climate models project higher temperatures, more variability in precipitation, and more extreme weather events in the future. Under such changing environments, foundation plant species, which promote stable conditions for other species and support fundamental ecosystem processes, may benefit from microbial partners that enhance plant survival during climate extremes. However, whether microbial partners can help to buffer ecosystems against climate change remains unknown. This research investigates a widespread, but poorly known, group of fungi that commonly grow in the roots of dominant forage grasses. The project determines how the benefits of these fungi vary along gradients of drought and heat stress, differ among grass species, and shift across geographic regions -- from the deserts of New Mexico to the tallgrass prairies of eastern Kansas. By filling these key knowledge gaps, this work has high promise for identifying fungi that help plants survive and grow in stressful climates. Deeper insight into the biology of root endophytes has the potential to transform understanding of how plants respond to drought and heat in the same way that studies on mycorrhizal fungi overturned paradigms about how plants acquire nutrients. This project tests whether root-associated fungi moderate the loss of net primary production during droughts and heat waves by benefiting grass species that dominate grasslands. The work addresses the following questions: (1) What is the relative importance of host species identity versus geographic/climatic gradients in explaining variation in symbiont abundance and composition? (2) How strongly do host species identity and geographic origin influence the magnitude of symbiont benefits across gradients of heat and drought stress? (3) Can symbiont-mediated amelioration of stress be generalized from laboratory settings to predict outcomes in the field? Activities include field surveys along latitudinal gradients, next-generation high-throughput sequencing of root fungi, development of a large fungal culture collection, multi-factor greenhouse trials that manipulate drought and heat, and field tests that leverage existing, large, cross-site rainfall experiment.
TESTING THE FUNGAL LOOP HYPOTHESIS FOR C AND N CYCLING IN DRYLAND ECOSYSTEMS
NSF 1557162 (to J. Rudgers et al.; 2016-2020; Total Award $1,522,132 UNM Award $730,297)
In forests and grasslands, decaying vegetation accumulates on the soil surface and is digested by communities of decomposer microorganisms. The end-products of decomposition serve as nutrients in the soil that, along with water, can be taken up by plants directly through their root systems. By contrast, deserts and other arid ecosystems have to play by a different set of rules. The lack of water means that plants are far more patchy in their distribution and grow in brief spurts following rare precipitation events. Between plant patches, a crust often forms consisting of surface-layer bacteria, fungi, lichens, and mosses. Soil crust fungi have extensions called hyphae that can make connections between crusted areas and plants. This project will examine implications of the "fungal loop hypothesis", which posits that subsurface fungal hyphae provide a network between plants and soil crusts that conserves and transports water and nutrients to plants. To test aspects of this hypothesis, researchers on this project will conduct field research at three different sites: the Chihuahuan Desert near El Paso, TX, the Colorado Plateau near Moab, UT, and a site between those, near Albuquerque, NM. At these sites, they will study the movement of water and nutrients through fungal hyphae and develop a framework for understanding when and where the fungal loop is most important. Drylands cover about 40% of Earth's surface and play essential roles in the planet's overall response to environmental change. The multi-site, field-intensive design of this project will also enable research and training opportunities for undergraduate and graduate students at two diverse institutions: the University of Texas at El Paso (UTEP) and the University of New Mexico (UNM).
In forests and grasslands, decaying vegetation accumulates on the soil surface and is digested by communities of decomposer microorganisms. The end-products of decomposition serve as nutrients in the soil that, along with water, can be taken up by plants directly through their root systems. By contrast, deserts and other arid ecosystems have to play by a different set of rules. The lack of water means that plants are far more patchy in their distribution and grow in brief spurts following rare precipitation events. Between plant patches, a crust often forms consisting of surface-layer bacteria, fungi, lichens, and mosses. Soil crust fungi have extensions called hyphae that can make connections between crusted areas and plants. This project will examine implications of the "fungal loop hypothesis", which posits that subsurface fungal hyphae provide a network between plants and soil crusts that conserves and transports water and nutrients to plants. To test aspects of this hypothesis, researchers on this project will conduct field research at three different sites: the Chihuahuan Desert near El Paso, TX, the Colorado Plateau near Moab, UT, and a site between those, near Albuquerque, NM. At these sites, they will study the movement of water and nutrients through fungal hyphae and develop a framework for understanding when and where the fungal loop is most important. Drylands cover about 40% of Earth's surface and play essential roles in the planet's overall response to environmental change. The multi-site, field-intensive design of this project will also enable research and training opportunities for undergraduate and graduate students at two diverse institutions: the University of Texas at El Paso (UTEP) and the University of New Mexico (UNM).
