Abstracts of Proposals Funded by the 2006 SWS Student Grant Program
Effects of Juncus effusus on native and exotic species in wetlands with contrasting fire and grazing regimes
Investigator: Elizabeth Boughton
University of Central Florida
Isolated wetlands comprise a significant part of the agricultural landscape in central Florida and understanding the response of wetland plant communities to agricultural management is essential for predicting the effects of alternative management scenarios or planning for ecological restoration. Restoration of wetlands in Florida has thus far been focused on hydrological restoration and little is known about plant community response to wetland management.
The objective of this study is to experimentally evaluate interactions between a dominant species, Soft Rush (Juncus effusus), and native and exotic species within different grazing regimes to determine if Soft Rush can benefit restoration of grazed wetlands. Soft Rush is an unpalatable plant that becomes dominant in grazed wetlands and palatable plants that associate with Soft Rush are protected from grazing. Thus Soft Rush may function to preserve native species in grazed wetlands. Positive interactions between plants, or facilitation, have been proposed as a tool for restoration in many areas, but exotic species have also been shown to benefit from plant facilitation to gain entry into communities. Therefore, interactions between Soft Rush and exotic species must be investigated before Soft Rush is used for wetland restoration.
This study will take place at MacArthur Agro-Ecology Research Center, a working cattle ranch in central Florida. The site has two different pasture types that represent an agricultural disturbance gradient, with “improved” pastures, in which uplands have been completely converted to exotic forage grass, and semi-native pastures in which uplands still contain a variety of native grasses. Experimental methods will include replicated treatment plots with and without Soft Rush and two grazing treatments (grazed and ungrazed) in wetlands of each pasture type and transplants of native and exotic species will be added to each plot. Species will be monitored for survival, vigor, and growth, and will be removed for biomass measurements at the end of the study. This study will enhance our understanding of the potential for using species interactions to restore wetlands, the importance of species interactions to exotic invasion of wetlands, as well as how the outcome of species interactions vary within different disturbance regimes.
Cryptic speciation and freezing tolerance in Melampus bidentatus (Pulmonate: Ellobiidae)
Investigator: Alice Dennis
Louisiana State University
The coffee bean snail, Melampus bidentatus, occurs in salt marshes and mangrove swamps between Nova Scotia and Texas. Northern populations tolerate winter freezing through the use of a protein that controls the rate and location of ice crystal formation. Transplant experiments have shown populations in Massachusetts and Delaware to be more cold tolerant than populations from South Carolina. The evolution of such adaptive differences can be hindered by high immigration between populations.
I will use genetic methods to determine the extent of population subdivision in M. bidentatus, to detect population changes associated with climate change, and to relate both of these to geographic variation in tolerance to freezing. Preliminary sequence from mitochondrial DNA suggests M. bidentatus is in fact a complex of two species that are physically indistinguishable. Genetic methods are thus the only way to identify the geographic range of each potential species. I will use mitochondrial sequence to assess population subdivision within M. bidentatus. In order to understand the origin of cold tolerance and to determine if it is a recently evolved trait in M. bidentatus, I will use mitochondrial and nuclear DNA sequence to determine the genealogical relationship between all Melampus species on the Atlantic coast of the Americas. This study will provide a new method to detect otherwise invisible ecological responses of wetlands species to climatic changes.
The effects of nutrient enrichment on benthic periphyton mat communities in two south florida coastal wetland habitats
Investigator: Josette La Hee
Florida International University
This project will examine benthic periphyton mats from two coastal wetland habitats located to the east of the Florida Everglades National Park, within Biscayne Bay National Park. The study will comprise two main parts. The first will examine the taxonomic components, physical architecture and productivity of these periphyton communities, in order to describe the composite groups within the mat and discern their functional roles. The second part will examine the processes of change that occur in periphyton communities exposed to consistent nutrient enrichment over an extended period and determine whether eutrophic conditions stimulate periphyton mat disintegration, a phenomenon that has thus far only been documented in floating periphyton mats within long-hydroperiod Everglades marshes.
The study will be conducted over a 4 month period in two coastal wetland habitats (a freshwater marsh and a brackish water mangrove swamp). Each habitat will have 3 enriched sites which will be exposed to a weekly dosing of 1000 µgL-1 Sodium Phosphate, and 3 control sites which will remain un-enriched. Pieces of periphyton mat will be placed at control and enriched sites and monitored for a 4 month period. Samples of periphyton will be collected and examined on a weekly basis in order to document temporal changes in mat composition, structure and productivity following enrichment.
This project will provide important baseline information regarding the composition and function of the coastal wetland benthic periphyton community, about which very little is currently known. By investigating the process of change that occurs following nutrient enrichment, it will be possible to create conceptual models that describe expected patterns of community change following enrichment. These models can then be used to aid in predicting possible outcomes of certain management decisions, such as the planned restoration of natural water flow patterns within the Everglades. The information gained will also be invaluable in the development of monitoring schemes that employ the use of indicator species and species assemblages as early detectors of change within the wetland system, before more permanent, large scale changes occur. This project is therefore highly significant to wetland conservation as well as the general study of wetland ecology.
Existence and controls of alternative stable states in temporary wetlands
Investigator: Sigrid Smith
University of Illinois at Urbana – Champaign
Biologists often observe starkly contrasting communities in seemingly identical environments. One theory suggests that these differences result from the existence of alternative stable states--multiple possible community structures that are equally likely in certain environmental conditions. While many examples of alternative stable states have been proposed, few experiments have rigorously demonstrated their existence. Further, while the presence of alternative stable states can have major consequences for ecosystem structure and stability, wetlands have received little study for this important feature.
Evidence suggests that three alternative stable states exist in temporary and semipermanent ponds within temporary wetlands, dominated by different producers: (1) floating plant mats, (2) submerged plant beds, and (3) phytoplankton blooms. This spring, I will demonstrate rigorously whether alternative stable states exist in temporary wetlands with a field experiment shifting the state of the producers.
In this experiment, I will remove floating plants and monitor ecosystem responses to determine whether the systems shift back to their original floating-dominated state or remain in a new phytoplankton-dominated state. I will also continue an ongoing study in which I periodically survey 25 ponds to explore the presence and potential controls of these differences in vegetation. These studies, together with laboratory experiments and mathematical modeling, will improve our understanding of the existence and controls of alternative stables states in temporary wetlands.
In addition, this research will greatly improve our ability to effectively manage natural and restored temporary wetlands, which are major foci of conservation efforts. The research will help us prevent ecosystem shifts to less desirable states (e.g., mat-forming plant outbreaks), and more generally it help us choose the most effective strategies to maintain stability and diversity in temporary wetlands.
Assessing hyperspectral wetland plant species variability and invasive identification
Investigator: Nathan Torbick
Michigan State University
In order to make decisions and shape policies to address today’s wetland related issues, increased and improved information is needed. Multispectral remote sensing has been shown to be useful in mapping and monitoring wetlands; however, the information provided is limited in achievable detail by sensor resolutions. New remote sensing technologies that capture narrow spectral band information can add significant advances for addressing complex wetlands monitoring and mapping questions. The primary question addressed here is whether individual species can be identified.
This study has three overlapping objectives. The first is to identify the optimal wavelengths for separating wetlands species utilizing field-level hyperspectral data. The second is to characterize the spectral variability of individual species. The third is to identify species of interest, invasives and exotics in this case, using a shape filter that incorporates plant species reflectance variability. The study will be carried out in a large fresh water wetland complex located in the Lower Muskegon River Watershed of Michigan, USA. Principal Component Analysis, Dissimilarity and Jefferies-Matusita statistical measures will be used to quantify optimal wavelengths and spectral discrimination abilities. A shape filter approach will detail invasive identification capabilities. Expected outcomes will quantify the strengths of particular wavelengths useful in wetlands mapping science and develop approaches for invasive species monitoring.
Patterns of macroinvertebrate diversity and community structure across a gradient of river-floodplain connectivity
Investigator: Brad Williams
University of Central Arkansas
We have only recently begun to realize the importance of flood events in the functioning of floodplain ecosystems. During floods, the hydrologic connection between a river and its floodplain has been shown to stimulate primary and secondary productivity through the exchange of dissolved nutrients and organic matter. Hydrologic connectivity may also be a strong mechanism influencing the community structure and diversity of aquatic organisms by increasing habitat heterogeneity. River management practices that facilitate commercial transport and control seasonal flooding disrupt the timing, duration, and ability of natural flood pulses to inundate floodplains. The importance of maintaining a natural level of hydrologic connectivity in regulated river floodplains has become an important area of research, but only a limited number of studies have examined the effects of connectivity on macroinvertebrate diversity and community structure. This is unfortunate since macroinvertebrates are crucial to the health and functioning of aquatic ecosystems.
I will determine the effects of river-floodplain connectivity on macroinvertebrate community structure and diversity patterns by sampling macroinvertebrates within the vegetated shoreline of twelve floodplain waterbodies with different degrees of connectivity to the Arkansas River. I will use a method of diversity partitioning to examine diversity patterns across multiple temporal and spatial scales. The findings of this study will lead to a better understanding of how river-floodplain connectivity influences the patterns of macroinvertebrate diversity and community structure in large river floodplains, and could potentially lead to the development of more effective management, conservation, and restoration strategies. This study will also provide much needed base line data on Arkansas River macroinvertebrate communities prior to the implementation of an extensive dredging operation, which will begin in late 2006. This operation will deepen the main channel by 1 m, and has the potential to drastically alter the hydrologic conditions of floodplain habitats.
