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2000 Progress Report: Subalpine Marsh Plant Communities as Early Indicators of Ecosystem Stress
EPA Grant Number: R825433C033Subproject: this is subproject number 033 , established and managed by the Center Director under grant R825433
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: EERC - Center for Ecological Health Research (Cal Davis)
Center Director: Rolston, Dennis E.
Title: Subalpine Marsh Plant Communities as Early Indicators of Ecosystem Stress
Investigators: Rejmankova, Eliska
Institution: University of California - Davis
EPA Project Officer: Levinson, Barbara
Project Period: October 1, 1996 through September 30, 2000
Project Period Covered by this Report: October 1, 1999 through September 30, 2000
RFA: Exploratory Environmental Research Centers (1992)
Research Category: Center for Ecological Health Research , Targeted Research
Description:
Objective:To relate variations in marsh plant species assemblages and nutrient dynamics to watershed properties to study the relationship between landscapes and wetland ecosystems.
Progress Summary:Because of their position in the landscape at the interface of aquatic and terrestrial ecosystems, wetlands play an integral role in watershed dynamics. However, rather than being simple ecotones, existing solely as a gradation between upland and lake, wetlands are distinct ecosystems, with unique biological, geochemical and hydrological properties and processes. These properties, which are important at the landscape scale in nutrient dynamics, sediment movement and biodiversity, serve to buffer the effects of terrestrial disturbances on the lake community. There is a strong need for site-specific studies on wetland processes in the Sierra Nevada and the Lake Tahoe Basin to characterize the role of wetlands in watershed dynamics.
A common but frequently ignored problem faced in wetland research is that many wetlands are connected by hydrologic mechanisms to a terrestrial watershed whose characteristics influence wetland structure and function. Subalpine marshes of the Sierra Nevada are strongly connected to watershed properties in that they are almost wholly dependent on surface and groundwater runoff from the watershed. During the active summer growing season the precipitation in the Sierra Nevada is extremely low accounting for less than 5 percent of the annual total. The watershed landscape strongly influences the chemical qualities and hydroperiod of the snowmelt-dominated runoff through contact with vegetation, soils and geological substrate. Because of this connection between wetland and terrestrial ecosystems, important aspects of species biodiversity and biogeochemistry in these marshes are strongly tied to properties of the surrounding watershed, such as vegetation, soils, disturbance (e.g., fire, erosion), land use (e.g., timber, grazing), management (e.g., wilderness areas) and population.
Our research in subalpine wetlands of the Lake Tahoe Basin addresses wetland ecology at a range of spatial and temporal scales from the landscape to the individual marsh. By examining (1) how multiple stresses directly affect the wetland ecosystem (e.g., disturbance, hydrological alteration), (2) how indirect factors at the landscape level affect the wetland ecosystem (e.g., watershed size, vegetation, land uses), and (3) how wetlands modify the biogeochemical processes that contribute to the Lake Tahoe dynamics, we are taking an approach that mirrors the interconnections of wetlands with aquatic and terrestrial systems. With an understanding of wetland dynamics and their relationship to landscape processes, subalpine wetlands in the Sierra Nevada can be better managed for protection of their beneficial uses.
While considerable research has gone into elucidating the effects of freshwater wetlands on watershed processes (e.g., water quality downstream, groundwater recharge), much less has been done to address the effects of the watershed on wetlands. Our research attempts to address this knowledge gap, searching for patterns in the linkages between the wetland and watershed ecosystems that will provide the framework for generating mechanistic hypotheses for experimental research. Because the research is interdisciplinary (e.g., hydrogeology, soil science, plant ecology), many questions are simultaneously being addressed with the data collection.
Work has already been completed which establishes our ability to monitor the distribution and abundance of the dominant marsh species using remote sensing. Subalpine marshes in approximately thirty different watersheds in an area of the northern Sierra Nevada extending in a ca. 50 mile radius from Lake Tahoe have been botanically surveyed. A GIS database of subalpine marshes in the Lake Tahoe Basin was constructed, describing geographic location, size, elevation and potential levels of disturbance. Watersheds that provide water to these marshes were then quantitatively characterized in additional GIS layers, by combining existing data layers and new layers created for this project. Relationships among plant community species compositions and watershed properties are currently being analyzed.
To reveal the historical change of watershed and wetland plant communities and condition, sediment cores of subalpine marshes in and around the Lake Tahoe basin, where an extensive record of human activities is available, were collected covering a range of sites of different levels of human impact. Pollen composition and physical and chemical characteristics of sediment cores showed the environmental changes according to human activities around Tahoe. Road construction and maintenance activities were well recorded in the core but an increased sedimentation rate and cation concentration. The plant community of Pope Marsh has been affected by water level change in Lake Tahoe and maintenance of Tahoe Keys. Also, the increase in motor vehicles affected the lead level in the marshes near roads.
To determine factors affecting sedimentation rate, sediment cores were collected in 11 marshes that have diverse environmental settings and sedimentation rates were determined by lead 210 dating method. Generally, sedimentation rates were related to human activities in the watershed or around the wetland but it was impossible to relate sedimentation rate to combined anthropogenic impact level. The sedimentation rate and sediment components in a wetland were changed according to human activities around the wetland. Road construction and maintenance was statistically responsible for the change in sedimentation rate. This analysis suggested that almost all of the wetlands studied still retain their pristine condition. However, it also showed that a slight increase in human activities has the possibility of degrading this condition.
Ecological relationships between wetlands and watersheds. Correlations among plant community compositions and watershed properties will provide information on the ecological connections between these ecosystems, and will generate mechanistic hypotheses on the nature of these connections. Two multivariate ordination and classification techniques are well suited to this type of problem: canonical correspondence analysis (CCA) and two-way indicator species analysis (TWINSPAN). These techniques provide a classification of sites according to vegetation characteristics (TWINSPAN), and which relate species and species assemblages to measured environmental variables (CCA). Initial analysis indicates that the vegetation is responding most strongly to geographic factors (primarily elevation) and to local levels of disturbance. One notable watershed-level characteristic that is significantly related to vegetation structure is the amount of urbanization in the watershed. Path analysis will be employed to test various models of functional relationships. Linkages that are established between wetland and forest ecosystem processes and properties will provide a means of rapidly detecting changes in long-term ecosystem processes occurring on a large spatial scale.
Evaluation of human activities on nutrient and sediment inputs to wetlands. It would be worthwhile to collect long sediment core to decide relative importance of anthropogenic impacts compared to long-term historical change. Also, we will integrate our studies of marsh sedimentation patterns with ongoing projects conducted by the Tahoe Research Group (TRG; see Sections C.2a and C.2b). Marsh sedimentation patterns will be compared to watershed erosion rates in the same watershed, which will link patterns with processes; and to sedimentation patterns in Lake Tahoe, which will provide a comparison of sedimentation patterns in two contrasting but adjacent ecosystem.
Potential impact of changes in nutrient limitation on wetland community and ecosystem properties. While the final analysis of data gathered in the previous phases of our research on subalpine marshes is being conducted, we are initiating a new area of research that builds on the existing information. Long term research of the Tahoe Research Group has documented an important change in limiting resources in the Lake Tahoe, specifically, the switch from a nitrogen-limited ecosystem to a phosphorus- limited ecosystem. Since the resource availability is not only of crucial importance for the lake ecosystem but also a driving force in structuring plant communities, we ask three questions. 1) Have changes in nutrient limitation observed at the lake level impacted plant communities in the transitional zones, i.e., wetlands? 2) What community level, and consequently, ecosystem level changes can we expect following human alteration of nutrient cycling in the Tahoe watershed? 3) From our ongoing studies we have the information on the nitrogen/phosphorus ratios in sediments in representative wetlands over time (J. Kim) and on the species composition of wetlands exposed to various levels of human disturbance (H. Spanglet). We use two concepts that have recently received increased attention in ecological literature: (1) N:P ratio of the vegetation directly indicates the nature of nutrient limitation on a community level (Koerselman & Muelman 1996; Meerts 1997), and (2) Potential nutrient resorption and resorption profficiency provide an objective gauge by which to measure the success of resorption as a nutrient conservation mechanism (Killingbeck 1996).
Nutrient budgets in subalpine wetlands and a new test of enzyme activities in soil and litter as an early indicator of ecosystem stress. Previous studies showed different sedimentation rates at different wetlands but it was difficult to tease out which factors are related to this difference. In general, sedimentation rate is decided by the balance of input and output of material. Material input includes in-site production and input from watershed or atmosphere and output includes decomposition and output through water flow. To decide the relative contribution of each factor in the different sedimentation rates in this region, we will measure the aboveground plant standing mass (instead of NPP) and decomposition rate. With the assumption that the amount of atmospheric input is the same in all wetlands in this region, allochthonous input will be decided from the balance of net primary productivity, decomposition rate, and sedimentation rate. Enzymes are ultimately responsible for the decomposition of organic material and enzyme activity will be determined in soil and litter in a litterbag experiment. The literature reports that the early respiration rate in litter can be used as an indicator of long-term decomposition rate. We would like to test the possibility of using enzyme activities in soil and litter as another indicator of long-term decomposition. Such measurments would be useful as an early indicator of ecosystem stress because microorganisms are much more sensitive than higher plants or animals. We will analyze enzyme activities in wetlands covering a range of sites with different levels of human impact.
Supplemental Keywords:Ecosystem Protection/Environmental Exposure & Risk, Water, INTERNATIONAL COOPERATION, Geographic Area, Scientific Discipline, RFA, ECOSYSTEMS, Ecosystem/Assessment/Indicators, Water & Watershed, Restoration, Aquatic Ecosystem Restoration, Aquatic Ecosystems & Estuarine Research, Terrestrial Ecosystems, Ecological Monitoring, Aquatic Ecosystem, Ecological Indicators, Biochemistry, Watersheds, Environmental Chemistry, Ecological Effects - Environmental Exposure & Risk, Ecosystem Protection, Monitoring/Modeling, Environmental Monitoring, State, lakes, water quality, California (CA), wildlife habitat, watershed modeling, watershed land use, watershed, watershed management, watershed restoration, hydrologic modeling, ecology assessment models, environmental stress indicators, anthropogenic effects, fish habitat, land use, wetlands, watershed development, Lake Tahoe, aquatic habitat, marsh plants, agricultural watershed, aquatic ecosystems, environmental stress, lake ecosysyems, watershed sustainablility, biogeochemcial cycling, ecological assessment, hydrology, water management options, ecosystem stress, ecosystem response, ecosystem monitoring, biodiversity, nutrient dynamics, integrated watershed model
Progress and Final Reports:
Original Abstract
Final Report
Main Center Abstract and Reports:
R825433 EERC - Center for Ecological Health Research (Cal Davis)
Subprojects under this Center:
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R825433C001 Potential for Long-Term Degradation of Wetland Water Quality Due to Natural Discharge of Polluted Groundwater
R825433C002 Sacramento River Watershed
R825433C003 Endocrine Disruption in Fish and Birds
R825433C004 Biomarkers of Exposure and Deleterious Effect: A Laboratory and Field Investigation
R825433C005 Fish Developmental Toxicity/Recruitment
R825433C006 Resolving Multiple Stressors by Biochemical Indicator Patterns and their Linkages to Adverse Effects on Benthic Invertebrate Patterns
R825433C007 Environmental Chemistry of Bioavailability in Sediments and Water Column
R825433C008 Reproduction of Birds and mammals in a terrestrial-aquatic interface
R825433C009 Modeling Ecosystems Under Combined Stress
R825433C010 Mercury Uptake by Fish
R825433C011 Clear Lake Watershed
R825433C012 The Role of Fishes as Transporters of Mercury
R825433C013 Wetlands Restoration
R825433C014 Wildlife Bioaccumulation and Effects
R825433C015 Microbiology of Mercury Methylation in Sediments
R825433C016 Hg and Fe Biogeochemistry
R825433C017 Water Motions and Material Transport
R825433C018 Economic Impacts of Multiple Stresses
R825433C019 The History of Anthropogenic Effects
R825433C020 Wetland Restoration
R825433C021 Sierra Nevada Watershed Project
R825433C022 Regional Transport of Air Pollutants and Exposure of Sierra Nevada Forests to Ozone
R825433C023 Biomarkers of Ozone Damage to Sierra Nevada Vegetation
R825433C024 Effects of Air Pollution on Water Quality: Emission of MTBE and Other Pollutants From Motorized Watercraft
R825433C025 Regional Movement of Toxics
R825433C026 Effect of Photochemical Reactions in Fog Drops and Aerosol Particles on the Fate of Atmospheric Chemicals in the Central Valley
R825433C027 Source Load Modeling for Sediment in Mountainous Watersheds
R825433C028 Stress of Increased Sediment Loading on Lake and Stream Function
R825433C029 Watershed Response to Natural and Anthropogenic Stress: Lake Tahoe Nutrient Budget
R825433C030 Mercury Distribution and Cycling in Sierra Nevada Waterbodies
R825433C031 Pre-contact Forest Structure
R825433C032 Identification and distribution of pest complexes in relation to late seral/old growth forest structure in the Lake Tahoe watershed
R825433C033 Subalpine Marsh Plant Communities as Early Indicators of Ecosystem Stress
R825433C034 Regional Hydrogeology and Contaminant Transport in a Sierra Nevada Ecosystem
R825433C035 Border Rivers Watershed
R825433C036 Toxicity Studies
R825433C037 Watershed Assessment
R825433C038 Microbiological Processes in Sediments
R825433C039 Analytical and Biomarkers Core
R825433C040 Organic Analysis
R825433C041 Inorganic Analysis
R825433C042 Immunoassay and Serum Markers
R825433C043 Sensitive Biomarkers to Detect Biochemical Changes Indicating Multiple Stresses Including Chemically Induced Stresses
R825433C044 Molecular, Cellular and Animal Biomarkers of Exposure and Effect
R825433C045 Microbial Community Assays
R825433C046 Cumulative and Integrative Biochemical Indicators
R825433C047 Mercury and Iron Biogeochemistry
R825433C048 Transport and Fate Core
R825433C049 Role of Hydrogeologic Processes in Alpine Ecosystem Health
R825433C050 Regional Hydrologic Modeling With Emphasis on Watershed-Scale Environmental Stresses
R825433C051 Development of Pollutant Fate and Transport Models for Use in Terrestrial Ecosystem Exposure Assessment
R825433C052 Pesticide Transport in Subsurface and Surface Water Systems
R825433C053 Currents in Clear Lake
R825433C054 Data Integration and Decision Support Core
R825433C055 Spatial Patterns and Biodiversity
R825433C056 Modeling Transport in Aquatic Systems
R825433C057 Spatial and Temporal Trends in Water Quality
R825433C058 Time Series Analysis and Modeling Ecological Risk
R825433C059 WWW/Outreach
R825433C060 Economic Effects of Multiple Stresses
R825433C061 Effects of Nutrients on Algal Growth
R825433C062 Nutrient Loading
R825433C063 Subalpine Wetlands as Early Indicators of Ecosystem Stress
R825433C064 Chlorinated Hydrocarbons
R825433C065 Sierra Ozone Studies
R825433C066 Assessment of Multiple Stresses on Soil Microbial Communities
R825433C067 Terrestrial - Agriculture
R825433C069 Molecular Epidemiology Core
R825433C070 Serum Markers of Environmental Stress
R825433C071 Development of Sensitive Biomarkers Based on Chemically Induced Changes in Expressions of Oncogenes
R825433C072 Molecular Monitoring of Microbial Populations
R825433C073 Aquatic - Rivers and Estuaries
R825433C074 Border Rivers - Toxicity Studies