Subalpine Wetlands as Early Indicators of Ecosystem Stress

EPA Grant Number: R825433C063
Subproject: this is subproject number 063 , 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 Wetlands as Early Indicators of Ecosystem Stress
Investigators: Rejmankova, Eliska
Institution: University of California - Davis
EPA Project Officer: Levinson, Barbara
Project Period: June 30, 1995 through June 30, 1998
RFA: Exploratory Environmental Research Centers (1992) RFA Text |  Recipients Lists
Research Category: Center for Ecological Health Research , Targeted Research


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, serving solely as a gradation between upland and lake, wetlands are ecosystems, with biological, geochemical and hydrological properties and processes unique to themselves. These emergent 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. Studies of subalpine wetlands in the Rocky Mountains have established their importance in biogeochemical, physical and biodiversity processes there, but unfortunately the results are not readily applicable to the Sierra Nevada, due to significantly different summer climates and hydrology. There is therefore a strong need for site-specific studies on these processes in the Sierra Nevada and the Lake Tahoe Basin to characterize the role of wetlands in watershed dynamics.


The investigators 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 stresses at the landscape level affect the wetland ecosystem (e.g., watershed erosion, 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.

A common problem faced in wetland research, but which is frequently ignored, 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 very 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) and population have a strong influence on the wetlands.

Investigators' research to date has addressed the nature and strength of connections between wetland and watershed ecosystems, and considers subalpine wetlands as indicator communities to monitor the state of the entire forested montane ecosystem. Many properties of Sierra Nevada subalpine marsh plant communities suggest their suitability as landscape-level indicators, such as their hydrologic connection to the watershed, domination by herbaceous plant species that can respond rapidly to environmental changes, organization of species into distinct zones that respond over time to environmental changes, and their amenability to monitoring through remote sensing due to strong differences among the dominant plant species in canopy structure. These qualities suggest that they are responsive to ecological change at both the local and landscape scales, and that these changes can be easily monitored. Using these combinations of ecological and physical characteristics, they are studying the ecological connections between wetlands and watersheds to learn how to interpret changes in marsh plant community composition in terms of watershed properties; and to develop reliable and economical assessment methods using remote sensing.

Work has already been completed which establishes the investigators’ ability to monitor the distribution and abundances of the dominant marsh species using remote sensing. Data on species composition of marshes in watersheds of different state (i.e., disturbance, human population) and land-uses (e.g., timber production, grazing, wilderness) have been collected in the area of Lake Tahoe. Relationships among plant community species compositions and watershed properties are currently being analyzed; preliminary observations of the data set indicate significant differences among these marshes that appear to vary in relation to levels of watershed disturbance.

Expected Results:

A base of data that relates variations in marsh plant species assemblages to watershed properties will provide information on the relationships between landscapes and wetland ecosystems that is generalizable to other similar environments, and will allow assessment of the indicator functions. 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. The research proposed is an attempt 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. Specifically, the current research consists of:

  • Determining species compositions of subalpine marsh plant communities in watersheds of different condition (land-uses, disturbance levels, management practices),
  • Determining correlations that exist between plant community structure and watershed condition; and
  • Developing methods of using satellite remote sensing to monitor marsh plant populations.

Research is expected to be directed towards investigating the effects of ecological stress from the local to landscape scale. We will continue investigating the influence of watershed dynamics on wetland functioning, and will expand our research in two directions: the interrelations of landscapes and wetlands (effects of landscape processes on wetlands, and the role of wetlands in landscape processes) and the local processes that structure and maintain subalpine marsh communities. Because the research is interdisciplinary (e.g., hydrogeology, soil science, plant ecology), many questions will be simultaneously addressed.

Supplemental Keywords:

Aquatic ecosystem, California, Sierra Nevada, environmental assessment, biodiversity, nutrients, wetlands, ecological indicators, ecosystem stress, land use, remote sensing., RFA, Scientific Discipline, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Ecology, Aquatic Ecosystems & Estuarine Research, Ecosystem/Assessment/Indicators, Ecosystem Protection, exploratory research environmental biology, Aquatic Ecosystem, Ecological Effects - Environmental Exposure & Risk, Monitoring/Modeling, Ecology and Ecosystems, Ecological Risk Assessment, West Coast, Ecological Indicators, wetlands, monitoring, stressors, watersheds, ecosystem indicators, Lake Tahoe, subalpine wetlands, wetland responses

Progress and Final Reports:

1996 Progress 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