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2000 Progress Report: Identification and distribution of pest complexes in relation to late seral/old growth forest structure in the Lake Tahoe watershed
EPA Grant Number: R825433C032Subproject: this is subproject number 032 , 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: Identification and distribution of pest complexes in relation to late seral/old growth forest structure in the Lake Tahoe watershed
Investigators: Rizzo, David
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 identify major pest complexes (pathogens, insects) associated with overstory and understory mortality, and reduced vigor in both late seral/old-growth (LSOG) and early seral forest stands in the Tahoe basin.
Progress Summary:If we are to obtain an accurate idea of the effects of abiotic (e.g., drought, fire) and human-induced stress factors (e.g., pollution, urbanization, timber management) on forest ecosystems, we must have a detailed picture of naturally occurring biotic stress factors. Many pathogens and insects are considered to be major pests of forest ecosystems and, therefore, detrimental to management goals. However, the fact that many of these organisms are native to these sites (with the exception of white pine blister rust) indicates that they may also play key roles in ecosystem functions (e.g., directing succession, maintaining biodiversity, decomposition, or providing food for wildlife). While the importance of pathogens and insects in natural forests has been acknowledged by ecologists, relatively few studies have directly assessed their role in the dynamics of these ecosystems. In the Lake Tahoe watershed, studies of late-seral/old-growth forest stands will provide baseline data on the importance and distribution of pest organisms prior to Euroamerican settlement, while studies of early seral stages will detect current patterns of mortality and stress. In addition, we have examined pest incidence and host mortality at other study sites in the Sierra Nevada and in Baja California. The combination of data from all of our study sites will contribute to current models which relate to ecosystem health.
While much tree mortality in the Lake Tahoe Basin can be indirectly attributed to the short-term effects of the recent drought and the long term effects of fire suppression, the proximal cause of death of most trees in the basin is due to a number of insects and pathogens. For each of the major conifer species, overall pathogen and insect incidence is generally lower on late-seral/old-growth sites as compared to seral stands. On seral sites, as a whole, 39 % and 49 % of all Jeffrey pine and white fir stems, respectively, were identified with some pest species. Old growth sites, as a whole, had pest incidence of 23 % and 34 % on Jeffrey pine and white fir. However, there was wide variation in pest incidence from site to site and between the different pest species and these overall differences between seral and late-seral/old growth stands were not statistically significant. In the past two years we have focused on two important tree pathogens in the Lake Tahoe Basin: dwarf mistletoe (Arceuthobium spp.) and white pine blister rust (Cronartium ribicola).
In order to understand Arceuthobium patterns of spread, host effects, and bark beetle interactions in the Sierra Nevada we chose to study dwarf mistletoe in 2 different areas (with different management histories) and 2 different Arceuthobium species over 3 study sites. Our objectives were: 1) determine the relationships of dwarf mistletoe with host variables, bark-beetles, and mortality, 2) assess the spatial pattern of Arceuthobium on white fir in two different mixed-conifer locations in the Sierra Nevada, and 3) determine if different species of Arceuthobium on their respective conifer hosts have similar spatial distributions within a one hectare area. We found the highest prevalence of dwarf mistletoe on Jeffrey pine in the Lake Tahoe Basin (87%), followed by dwarf mistletoe on white fir in Lake Tahoe (30%), with the lowest prevalence on white fir at the Teakettle Experimental Forest (27%). We found that dwarf mistletoe prevalence and severity on white fir in our Lake Tahoe grid was not correlated to density but severity was significant and positively correlated to host size. At the Teakettle Forest, dwarf mistletoe prevalence and severity on white fir was significantly correlated with host density and host size. Dwarf mistletoe prevalence and severity on Jeffrey pine was significantly and positively correlated with host density but severity was not correlated with host size. Individuals, of both white fir and Jeffrey pine, in all diameter size classes are susceptible to dwarf mistletoe with the lowest infection rate in the seedling-10 cm diameter size class. Arceuthobium on white fir in Lake Tahoe showed a certain degree of spatial aggregation up to 40 meters. However, random spatial patterns were found for Arceuthobium on Jeffrey pine in Lake Tahoe and on white fir at the Teakettle Forest.
In 1999 and 2000, we have concentrated our efforts in the subalpine zone looking at the distribution of an introduced pathogen. White pine blister rust (WPBR) caused by Cronartium ribicola is an exotic pathogen that infects and kills 5-needle pine species. In the Lake Tahoe Basin there are three species that are affected by this disease: sugar pine (Pinus lambertiana), western white pine (Pinus monticola) and whitebark pine (Pinus albicaulis). Western white pine grows in the transition zone between upper montane and the subalpine zone, whereas whitebark pine exists only in the subalpine zones. These two species are important components of these subalpine habitats and are valued for their roles in watershed protection and wildlife food at these higher elevations. Loss of these species from the subalpine landscape would have major ecological consequences.
To understand patterns of pathogen spread and the effect WPBR may have on host population dynamics, we surveyed 5-needle pine species in 30-40 ha grids in mixed-conifer forests in the central Sierra Nevada and in a subalpine location in the Lake Tahoe Basin, in the northern Sierra Nevada. In addition, we ran transects in 17 different upper montane/subalpine locations around Lake Tahoe. In mixed-conifer forests, our results suggest that WPBR incidence is largely dependent on topographic features, that favor environmental conditions suitable for rust infection, as well as the presence of Ribes. In the more environmentally homogenous subalpine location, WPBR incidence was less variable and more uniformly spread. However, across the Lake Tahoe Basin WPBR incidence is quite variable. Much of the variability associated with incidence across the Basin is due to differences in environmental conditions, and possibly genetic heterogeneity and isolation of hosts. Where environmental conditions are favorable for WPBR, we have observed increased mortality among smaller pine recruits.
Future Activities:This winter we intend to synthesize a wide range of data sets on forest tree mortality in the Lake Tahoe Basin. We will be collaborating with the US Forest Service remote sensing lab to integrate their coarse scale mortality numbers with our fine scale mortality numbers for the lower montane zone. This remote sensing data has previously been unavailable to us.
Pathogens and insects will always be a part of Lake Tahoe forest ecosystems and any management strategies designed to restore natural processes will need to take into consideration the effects on pest species. In theory, restoring forests to their natural densities should mitigate most serious pest outbreaks (e.g., reduced bark beetle epidemics during drought periods). However, procedures such as thinning dense understories and prescribed burns have the potential to increase pest incidence in some instances. For example, thinning may potentially mitigate pest problems by lowering stand densities and relieving the potential for drought and competition-induced stress. Such operations, however, often damage residual trees and can increase the buildup of root disease inoculum due to saprobic survival in stumps. The ecological consequences of these restoration methodologies are not well understood. Therefore, we are involved with an experiment to study the effects of logging (to reduce the fuel loads) and prescribed burning to restore open, late seral stage stands on the Teakettle Experimental Forest near Dinky Creek in the Sierra National Forest.
· We are examining the interactions of pathogens and insects with human
caused changes to forest ecosystems (e.g., fire suppression, logging) to determine
the current and future impacts on forest health in the Lake Tahoe Basin.
· Both native and exotic pests are the proximal cause of extensive tree
mortality observed in the Lake Tahoe Basin in the last decade.
· Numerous management/restoration strategies have been proposed for Lake
Tahoe forests, however, most of these treatment have not taken into consideration
how changes in pest dynamics will affect results.
· We intend to be involved with monitoring pathogens and insects during
the course of such treatments to determine if adaptive changes must be implemented
to avoid further forest health problems.
· We are also interested in continuing monitoring the progress of an
exotic disease, white pine blister rust, in the subalpine forests of the basin.
This disease has the potential to dramatically change forest dynamics in these
high elevation forests and therefore affect numerous wildlife species.
Ecosystem Protection/Environmental Exposure & Risk, ENVIRONMENTAL MANAGEMENT, Water, INTERNATIONAL COOPERATION, Scientific Discipline, RFA, ECOSYSTEMS, Ecosystem/Assessment/Indicators, Water & Watershed, exploratory research environmental biology, Restoration, Aquatic Ecosystem Restoration, Aquatic Ecosystems & Estuarine Research, Terrestrial Ecosystems, Ecological Monitoring, Aquatic Ecosystem, Ecological Indicators, Biochemistry, Environmental Microbiology, Ecological Effects - Human Health, Watersheds, Ecological Effects - Environmental Exposure & Risk, Ecosystem Protection, Monitoring/Modeling, Resources Management, water quality, ecological impact, lake ecosystem, forest tenure, watershed management, watershed restoration, ecosystem modeling, ecological restoration, deforestation, ecological research, aquatic habitat protection , pest complexes, ecosystem restoration, wetland restoration, forested basins, wetland plant species, conservation, GIS, forest ecosystems, aquatic ecosystems, ecosystem assessment, environmental stress, pathogens, vegetation , lake ecosysyems, biotic stress, deterministic linkages, ecological assessment, forest conservation, forests, restoration strategies, ecosystem stress, watershed assessment, ecological models, watershed forests, Sierra National Forest, biodiversity, ecological effects, restoration planning
Progress and Final Reports:
1999 Progress Report
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