Grantee Research Project Results
Final Report: The role of ecosystem processes in restoring local and regional species diversity in Coastal Plain wetlands
EPA Grant Number: R825795Title: The role of ecosystem processes in restoring local and regional species diversity in Coastal Plain wetlands
Investigators: Resetarits Jr., William J. , Fauth, John E.
Institution: University of Illinois Urbana-Champaign , College of Charleston
EPA Project Officer: Hahn, Intaek
Project Period: September 1, 1997 through August 31, 2000
Project Amount: $527,032
RFA: Ecosystem Restoration (1997) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Hazardous Waste/Remediation , Land and Waste Management , Aquatic Ecosystems
Objective:
The specific objective of this research project was to determine the impact of variation in hydroperiod and its attendant impact on the success of wetlands restoration efforts and the maintenance of diversity in complex mosaic landscapes. Pond drying is a form of disturbance that at intermediate levels should increase species diversity by preventing elimination of species through competition, and by preventing colonization of wetlands by predatory fishes. It also prevents the accumulation of other predators such as larval insects with long larval stages. Thus, maintaining a mosaic of pond hydroperiods may be critical to maintaining regional (watershed level) species diversity. The long-term objective of this research project was to identify and test hydroperiod manipulations that bring the amphibian faunas of artificially created wetland ponds closer to those of their natural counterparts, and to examine the mechanisms whereby diversity is affected by variation in hydroperiod. Amphibians are sentinel species that are good indicators of ecosystem health. Therefore, successful mitigation for frogs and salamanders should indicate restoration of ecosystem function affecting a broad range of organisms.
To rigorously address the role of hydroperiod variation and its attendant ecological changes in the maintenance of species diversity, this project utilizes both comparative and experimental approaches. Experiments were being conducted at both the whole pond and mesocosm level to examine the effects on diversity at both the phenomenological and mechanistic levels. To more fully understand the dynamics of complex wetland systems, we expanded the focus of our research to include detailed work on aquatic beetles, fish, and odonates. The success of our proposed restoration strategies for a variety of taxa was rigorously evaluated with a large-scale experimental test in man-made ponds, and the mechanisms whereby such changes are generated was examined in a variety of detailed field mesocosm experiments.
Summary/Accomplishments (Outputs/Outcomes):
Whole Pond Hydroperiod Manipulations
Ecological theory predicts ponds with intermediate hydroperiods will maintain the greatest diversity of amphibians, and other species with complex life cycles. We tested this hypothesis by experimentally draining two types of permanent, manufactured ponds: wildlife ponds and borrow pits. Wildlife ponds were intentionally created as wildlife watering holes, while borrow pits are aquatic habitats created when construction crews remove fill for roads. Both pond types, either by design (wildlife ponds), or by the nature of the initial use (borrow pits), have little variation in hydroperiod and tend to be permanent.
We imposed variation in hydroperiod in a large-scale experiment with a 2 x 2 x 2 x 3 design. The two pond types were drained either in summer alone, winter alone, both summer and winter, or never. Each of these eight treatments was replicated three times within the Francis Marion National Forest, South Carolina. Twelve nearby natural, temporary ponds were sampled for amphibians at the same time to assay natural patterns of variation in species richness and abundance. Pond-draining had tremendous effects on amphibian species richness, which varied significantly with pond type (see Figure 1). Species richness in borrow pits doubled, and increased 50 percent in wildlife ponds that were drained, compared to those left full. Summer draining increased species richness more than winter draining. In addition, amphibian abundance increased several orders of magnitude in ponds that were drained, compared to those left full. The results indicate that landscape level variation in hydroperiod is extremely important in maintaining regional species diversity. The results also indicated that pond-draining, which is another application of the intermediate disturbance hypothesis, can rapidly restore amphibian diversity in manufactured wetlands and function as a tool to manage regional diversity of a variety of different taxa. It underscores the importance of including spatial and/or temporal variation in hydroperiod in any restoration or mitigation activities. Such activities must be coordinated at the regional scale to assure maintenance and/or restoration of landscape level diversity.
Fire and Species Diversity in Wetland Systems
Fire is another form of disturbance that is expected to fit the intermediate disturbance hypothesis, and frequently is used as a management tool in terrestrial systems. Fire is applied far less frequently in wetland systems, especially within temporary ponds themselves. Therefore, its role in the maintenance of species diversity in these systems is poorly understood. Fire and hydroperiod obviously interact in the frequency. Intensity and impacts of fire within a wetland system are dependent on the dynamics of the hydroperiod. Fire alters the abundance and diversity of many species, but its effects on amphibians are poorly known. We tested whether prescribed burning affected amphibian abundance and diversity within the Francis Marion National Forest, South Carolina, by monitoring assemblages at 15 temporary ponds with five different burn histories: 0, 1, 3, 5, and 12 years after burns. We also monitored terrestrial and aquatic environmental variables likely to influence amphibian diversity, such as leaf-litter depth, pond water chemistry, and distance to neighboring ponds. Fire had significant negative effects on proximate measures of local diversity. Our results suggest decreasing frequency of prescribed burns from the current 2-3 years to 3-7 years will better maintain diverse amphibian and plant assemblages. Substituting growing-season burns for the current practice of winter and spring burns would avoid repeatedly interrupting amphibian breeding and maintaining the desired longleaf pine community.
Figure 1. Number of Amphibian Species by Pond Type
Variation in Predators as a Mechanism of Variation in Habitat Suitability and Species Diversity
The overall objective of this component of the research was to develop a better understanding of biotic factors that are thought to have a substantial influence on the functional role of predators, and to use that knowledge to understand the role of hydroperiod variation in generating differences in aquatic communities through its effect on the distribution of predators across the local and landscape level. Although it has long been known that predators can have a significant influence on many factors in natural communities (e.g., species diversity, community stability, and the distribution of species) it is not always clear what will be the effect. Careful examination of key factors could explain why different predator species and predator populations differ in their functional roles they play. Such information would be very useful in predicting the consequences of species loss, declining population sizes, and invading species. The factors that we examined are represented by: (1) physical and behavioral characteristics of different predator species; (2) relative abundances of prey species among communities; and (3) average body size and population density of different populations within a predator species. The research focuses on predator-prey interactions between fish and salamander predators and their tadpole prey in pond ecosystems. We specifically examined the functional equivalence of predators in natural communities, the ability of energetic models to predict the outcome of predator-prey interactions, and how keystone predation interacts with the relative abundance of prey species. The most striking conclusion was that predators show very little functional redundancy, even within genera, so that maintaining a diverse array of predators at both the local and landscape level is necessary to preserve the diverse functional roles played by predators in aquatic systems. The role of predators in maintaining ecosystem function likely derives from the diversity of functional roles played by different predators, rather than functional redundancy among predators.
Mechanisms of Community Assembly in Aquatic Habitats
We examined in detail how patterns of prey distribution and abundance are generated by examining alternative mechanism for determining how predation influences population and community level dynamics. We have spent considerable time and energy examining the mechanism whereby variation in hydroperiod, and the attendant effects on the distribution of predators among habitats, generates variation in species diversity both in aquatic beetle, odonates, and amphibians. We experimentally investigated how natural populations of ovipositing treefrogs and colonizing aquatic beetles partitioned their distribution amongst experimental ponds differing in the presence of a variety of fish predators, at differing levels of habitat complexity, with variation in nutrients, and variation in canopy cover. How patterns of species presence and abundance are generated, and how they vary in space and time, remain a central focus of community theory. However, individual communities embedded within larger landscapes are interconnected and interdependent in ways not typically considered, hence they require a metacommunity perspective. Individual habitats within such complex landscapes often are modeled as islands, but for many species, they are more appropriately patches containing varying levels of resources and risk. A critical feature defining both resources and risk is the distribution of other species across the landscape.
Habitat selection in response to species distributions is a particularly important contributor to community assembly both in individual communities and at larger spatial scales. We examined mechanisms whereby habitat selection among interconnected communities at the landscape level affects metacommunity dynamics by playing a central role in the process of community assembly. These mechanisms include: (1) community assembly driven by interspecific attraction and repulsion; (2) habitat selection effects on variation in population distribution in contrast to population size; (3) contagious avoidance (or attraction) and cascading habitat loss; and (4) habitat selection on multiple spatial scales. We examined how habitat selection can affect community assembly, the dynamics of natural metacommunities, and developing models of metacommunity dynamics. These results dramatically alter our view of processes affecting population and community level dynamics by demonstrating that behavior, in the form of habitat selection, can drive distribution/abundance patterns in the absence of actual variation in mortality by redistributing individuals among habitats within complex landscapes.
Journal Articles on this Report : 17 Displayed | Download in RIS Format
Other project views: | All 44 publications | 19 publications in selected types | All 17 journal articles |
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Binckley CA, Resetarits Jr. WJ. Reproductive decisions under threat of predation: squirrel treefrog (Hyla squirella) responses to banded sunfish (Enneacanthus obesus). Oecologia 2002;130(1):157-161. |
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Binckley CA, Resetarits Jr. WJ. Functional equivalence of non-lethal effects: generalized fish avoidance determines distribution of gray treefrog, Hyla chrysoscelis, larvae. Oikos 2003;102(3):623-629. |
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Binckley CA, Resetarits Jr. WJ. Habitat selection determines abundance, richness and species composition of beetles in aquatic communities. Biology Letters 2005;1(3):370-374. |
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Chalcraft DR, Resetarits Jr. WJ. Mapping functional similarity of predators on the basis of trait similarities. The American Naturalist 2003;162(4):390-402. |
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Chalcraft DR, Resetarits Jr. WJ. Predator identity and ecological impacts: functional redundancy or functional diversity? Ecology 2003;84(9):2407-2418. |
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Chalcraft DR, Resetarits Jr. WJ. Metabolic rate models and the substitutability of predator populations. Journal of Animal Ecology 2004;73(2):323-332. |
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Diana SG, Resetarits Jr. WJ, Schaeffer DJ, Beckmen KB, Beasley VR. Effects of atrazine on amphibian growth and survival in artificial aquatic communities. Environmental Toxicology and Chemistry 2000;19(12):2961-2967. |
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Eason GW, Fauth JE. Ecological correlates of anuran species richness in temporary pools: a field study in South Carolina, USA. Israel Journal of Zoology 2001;47(4):346-365. |
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Fauth JE. Identifying potential keystone species from field data – an example from temporary ponds. Ecology Letters 1999;2(1):36-43. |
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Fauth JE, Resetarits Jr. WJ. Biting in the salamander Siren intermedia intermedia: courtship component or agonistic behavior? Journal of Herpetology 1999;33(3):493-496. |
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Fauth JE. Standard field codes for North American amphibians. Herpetological Review 1999;30(3):135-136. |
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Fauth JE. Interactions between branchiate mole salamanders (Ambystoma talpoideum) and lesser sirens (Siren intermedia): asymmetrical competition and intraguild predation. Amphibia-Reptilia 1999;20(2):119-132. |
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Fauth JE, Resetarits Jr. WJ, Levesque EM. A cost-effective method for locating herpetofaunal field sites from the air. Herpetological Review 2000;30(4):216-217. |
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Resetarits Jr. WJ, Rieger JF, Binckley CA. Threat of predation negates density effects in larval gray treefrogs. Oecologia 2004;138(4):532-538. |
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Resetarits WJ. Colonization under threat of predation:avoidance of fish by an aquatic beetle, Tropisternus lateralis (Coleoptera:Hydrophilidae). Oecologia 2001;129(1):155-160. |
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Rieger JF, Binckley CA, Resetarits Jr. WJ. Larval performance and oviposition site preference along a predation gradient. Ecology 2004;85(8):2094-2099. |
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Schurbon JM, Fauth JE. Effects of prescribed burning on amphibian diversity in a southeastern U.S. national forest. Conservation Biology 2003;17(5):1338-1349. |
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Supplemental Keywords:
watersheds, wetlands, temporary ponds, ecological effects, ecosystem, functional redundancy, functional equivalence, habitat selection, hydroperiod, oviposition site choice, intermediate disturbance, fire, prescribed burning, species diversity, indicators, restoration, aquatic, habitat, conservation, ecology, zoology, surveys, experiments, Southeast, South Carolina, SC, Virginia, VA., RFA, Scientific Discipline, Water, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Water & Watershed, Midwest, Restoration, State, Monitoring/Modeling, Environmental Monitoring, Biology, Aquatic Ecosystem Restoration, Watersheds, wetlands, Iowa, diversity, wildlife, regional species diversity, frogs, biodiversity, environmental assets, amphibians, coastal environments, salamanders, species interactions, ecological recovery, aquatic ecosystems, IAProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.