Grantee Research Project Results

Final Report: Pre-contact Forest Structure

EPA Grant Number: R825433C031
Subproject: this is subproject number 031 , 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: UC Davis Center for Children's Environmental Health and Disease Prevention
Center Director: Van de Water, Judith
Title: Pre-contact Forest Structure
Investigators: Barbour, Michael
Institution: University of California - Davis
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 1996 through September 30, 2000
RFA: Exploratory Environmental Research Centers (1992) RFA Text |  Recipients Lists
Research Category: Center for Ecological Health Research , Targeted Research

Objective:

The objective of this research project was to reconstruct the architecture and species composition of forest vegetation of the Lake Tahoe watershed as it existed prior to 1850, and to quantify any post-1850 changes that might have affected the water quality of Lake Tahoe and its tributaries.

Summary/Accomplishments (Outputs/Outcomes):

A variety of resources and approaches were utilized to achieve the forest reconstruction. On the ground, we censused all likely old-growth polygons from a 1970 Forest Service vegetation survey, limiting our search to upper montane and lower montane zones. We located 37 stands that appeared to contain undisturbed, old-growth forest in four types: Jeffrey pine, mixed conifer, white fir, and red fir. We also collected litter and soil for an analysis of nutrient and decomposer content.

We summarized modern vegetation data for nearly 800 forest plots taken by the Forest Service in its Forest Inventory Analysis program to have a quantitative summary of seral (second-growth) forests so that we could determine the quantitative boundaries between old-growth and second-growth forest vegetation. We visited 22 of those seral sites for additional data, taken in a manner comparable to that used at our old-growth sites. We also collected litter and soil for an analysis of nutrient and decomposer content.

Working in cooperation with Dr. JoAnn Fites of the Forest Service, we also performed a geographic information system search of recently digitized aerial photographs of forest vegetation in the Lake Tahoe Basin to locate and measure the area of old-growth stands, based on interpretations of remotely sensed data. These approaches gave us an understanding of modern old-growth forest characteristics, but they could not reveal how today's old-growth vegetation might differ from that of pre-1850. Three sources of data for precontact forests were examined: (1) We studied "stump stands" that remain from clear cuts during 1875-1902 in the east side of the basin, where dry weather has preserved the stumps so that their age and species identity still can be determined. Alan Taylor discovered 17 of these clear cuts. Stumps as small as 10 cm in diameter were included in his analyses of half-hectare samples. (2) We studied general Land Office record books, in which surveyors noted the identity of witness trees along section lines and corners during the period 1870-1890. (3) We studied existing vegetation in the southern end of the Peninsular Range in Baja, California; the Sierra San Pedro Martir, where 60,000 ha of old-growth mixed conifer forest reside in a landscape that never has experienced logging or fire suppression management. This ecosystem appears to be an ecological equivalent to that of the Tahoe Basin in terms of geology, climate, and flora.

The following activities were accomplished:

• We located 37 old-growth forest stands within the Lake Tahoe Basin using global positioning system coordinates, written directions from the nearest roads or trails, permanently marked trees, and photographs. These stands can serve as valuable reference points and monitoring stations for further research and as public displays for many years into the future.

• We defined the minimal requirements for old-growth forests in terms of density of trees of certain sizes and ages, basal area, tree canopy cover, and shrub and herb cover. We made these definitions specific to four forest types (Jeffrey pine forest, mixed conifer forest, white fir forest, and red fir forest), and we quantitatively defined each forest type in terms of a range of importance values for overstory tree species.

• We determined that old-growth forests require 200-300 years of disturbance-free existence. Most secondary forests in the Lake Tahoe Basin are 100-140 years old; thus, the current management objective to move these stands to old-growth status could be achieved within 60 or more years.

• We determined that the modern ratio of 2.7 percent old-growth to 97.3 percent second-growth forest is vastly different from the precontact ratio of (at least) 55 percent old-growth to 45 percent second growth. The area of old-growth forests in the Lake Tahoe Basin has been reduced by 95 percent since 1850. Forest management objectives, however, should not attempt to convert most second-growth forest to old-growth status; rather, the objective should be to convert only one-half to old-growth status. Every successional stage has its particular suite of plant and animal species. Therefore, every successional stage should be represented in the future Lake Tahoe Basin landscape, if maximum biodiversity is to be maintained.

• Our evidence indicates that precontact old-growth forests in the Lake Tahoe Basin were significantly different from modern old-growth forests in several ways. Modern forests have approximately two to three times as many trees per unit area as in the past. It likely is that the increased density of trees causes more intensive competition for soil moisture. During drought years, the increased competition leads to twice as much mortality as would occur with precontact tree densities. This information could influence fire suppression management strategies.

• Our data show that modern forests have three to nine times as many fir trees as pine trees, in contrast to a past ratio of 1:1. Unknown ecosystem consequences may result from a shift in the dominant species of a community, but surely some herbivorous birds, insects, and mammals will respond to such a gross change in their cafeteria. Those who manage the monitoring of rare or endangered animal species should be concerned with this change.

• We suggest that the major factors responsible for changes in tree density and species composition over the past 150 years are clear cutting (which sets back succession), fire suppression management, the disappearance of Native Americans from the landscape, and climate change. These factors—especially the first two, because only those have the potential for reversal—should be kept in mind by management agencies.

• This particular project resulted in successful Ph.D. training and dissertations for two students, an M.S. degree and entrance into a Ph.D. program for one student, and mentoring and training for six undergraduate students. Two of those students are now in graduate programs and one student conducts natural resource conservation for a state agency.

Supplemental Keywords:

ecosystem, ecosystem protection, environmental exposure and risk, geographic area, international cooperation, water, terrestrial ecosystems, aquatic ecosystem, aquatic ecosystem restoration, aquatic ecosystems and estuarine research, biochemistry, ecological effects, ecological indicators, ecological monitoring, ecology and ecosystems, environmental chemistry, restoration, state, water and watershed, watershed, watershed development, watershed land use, watershed management, watershed modeling, watershed restoration, watershed sustainability, agricultural watershed, exploratory research environmental biology, California, CA, Clear Lake, Lake Tahoe, anthropogenic effects, aquatic habitat, biogeochemical cycling, ecological assessment, ecology assessment models, ecosystem monitoring, ecosystem response, ecosystem stress, environmental stress, environmental stress indicators, fish habitat, hydrologic modeling, hydrology, integrated watershed model, lake ecosystems, lakes, land use, nutrient dynamics, nutrient flux, water management options, water quality, wetlands., RFA, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, Air, INTERNATIONAL COOPERATION, Water, ECOSYSTEMS, ENVIRONMENTAL MANAGEMENT, Aquatic Ecosystem, Restoration, Aquatic Ecosystems & Estuarine Research, Ecological Indicators, Ecosystem Protection, Terrestrial Ecosystems, Aquatic Ecosystem Restoration, Atmosphere, Watersheds, Ecosystem/Assessment/Indicators, Environmental Microbiology, Air Pollution Effects, Ecological Monitoring, Biochemistry, climate change, Water & Watershed, Ecology and Ecosystems, Resources Management, lake ecosysyems, watershed management, wetland plant species, ecological effects, vegetation , restoration planning, water quality, biodiversity, ecological impact, restoration strategies, ecosystem assessment, forest conservation, lake ecosystem, watershed restoration, ecological assessment, ecological models, watershed assessment, environmental monitoring, forests, ecosystem stress, environmental stress, wetland restoration, integrated watershed model, deforestation, aquatic habitat protection , ecological research, forest tenure, aquatic ecosystems, ecosystem restoration, forested basins, GIS, watershed forests, anthropogenic stress, conservation, deterministic linkages, ecological restoration, ecosystem modeling

Relevant Websites:

http://ice.ucdavis.edu/cehr/ Exit

Progress and Final Reports:

Original Abstract

1997

1998

1999 Progress Report

Main Center Abstract and Reports:

R825433    UC Davis Center for Children's Environmental Health and Disease Prevention

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