Pacific Southwest Research Station

About Us: Research Accomplishments 2012

Explore the 2012 Report

1. Introduction
2. Interdisciplinary
   Strategies
3. PSW at a Glance
4. Experimental Areas
   & Partnerships
5. Community Service
6. Ecosystem Function
   & Health
7. Fire & Fuels
8. Urban Ecosystems
   & Social Dynamics
9. Conservation of
   Biodiversity
10. Organization
    & Locations

Research Accomplishments

• 2012 [pdf 4.9 MB]
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• 2011 [pdf 8.8 MB]
• 2010 [pdf 5.7 MB]
• 2009 [pdf 8.7 MB]

Ecosystem Function and Health Program

Andrzej Bytnerowicz. [Photo by Andrzej Bytnerowicz] In this photo a tree in the King's River Experimental Watershed is removed using mechanical thinning. [Photo by Sherri Eng]

Photo is of a PSW Fresno hydrologic technician downloading data during winter at a high elevation meteorology tower and rain gauge for the Bull Site of the Kings River Experimental Watersheds in the Sierra Nevada of California. [Photo by Sean Eagen]

Our forests and wildland ecosystems are exceedingly diverse and provide a wide array of societal goods and services. From clean water, timber and non-timber products, and carbon sequestration to recreational use, aesthetic beauty, and native biodiversity, these ecosystems are national treasures that contribute to the prosperity of current and future generations. A growing list of environmental pressures, including climate and land-use change, water scarcity, and an increasing human population, threaten the health and integrity of these ecosystems.

The Ecosystem Function and Health Program focuses on the interactions among changes in or brought about by biotic and abiotic factors, such as temperature and precipitation, invasive species, air pollution, insects, pathogens, and past and current land management actions. Station scientists conduct research that provides an integrated understanding of the biophysical conditions that threaten ecosystem resilience, including how environmental changes are initiated and progress, what thresholds are associated with these changes, and what the consequences are of crossing identified thresholds.

2012 Research Highlights

Prescribed burning and mechanical thinning pose little risk to forest ecology

Current conditions of many seasonally dry forests in the western and southern U.S., especially those that once experienced low- to moderate-intensity fire regimes, leave them uncharacteristically susceptible to high-severity wildfire. Using prescribed fire and mechanical thinning are generally successful in making stands more resilient to high-intensity wildfire. Station scientists and collaborators found that these fuel reduction methods can be conducted with few negative consequences to the ecosystem. While mechanical treatments do not serve as surrogates for fire, their application may help mitigate costs and liability in some areas. Treatment effects on fire hazard are transient, indicating that repeated applications are necessary to maintain desired effects.

Study shows sources of air pollution in the Lake Tahoe basin

Station scientists conducted a study in the Lake Tahoe Basin to address the distribution of ozone, its precursors, and nitrogen oxides. Scientists used passive samplers to monitor air quality at 34 sites located at various elevations in and around the basin. Scientists found that air pollution from the California Central Valley caused high concentrations of ozone on the western slope of the Sierra Nevada, but these emissions did not affect air quality in the Lake Tahoe Basin. Local emission sources are most likely the cause of elevated ozone levels at high elevation sites on the eastern side of the basin. These findings will help to develop management strategies aimed at improving air quality of the Lake Tahoe Basin.

Air pollution thresholds used to protect U.S. ecosystems

Advances in defining thresholds for acceptable air pollution exposure have greatly increased the capacity to protect and restore at-risk ecosystems. The use of these thresholds applies to impacts on aquatic and terrestrial ecosystems that are affected by pollutants, such as mercury, sulfur and excess nitrogen. This research will benefit air quality specialists, land managers, scientists, policymakers and the U.S. Congress. The critical loads developed in this work are being applied for natural resource protection by the Forest Service, National Park Service, and others. A federally-mandated peer reviewed report was also submitted to Congress providing an update on the status of pollutant emissions, atmospheric deposition, ecosystem effects, and projections of emissions necessary to prevent future adverse ecosystem effects in the U.S.

Photo is of an air pollution monitoring site with active ozone instrument and passive samplers in the White Mountains, which was taken during 2007. Research was conducted by collaborators from the USDA Forest Service Pacific Southwest Research Station, University of California, and the Saint Mary's College. [Photo by Andrzej Bytnerowicz]

Streamflow and water balance data to gauge the effects of a changing climate on California's water resources

Research at the Kings River Experimental Watershed in the southern Sierra Nevada has established the current and natural range of variability for headwaters watersheds for the first time. Reliable data collection and analysis is critical to answering vexing questions about how various silvicultural treatments impact water quality, quantity, and biodiversity. This is the only site that that can provide this information in the southern Sierra Nevada. Years of data will be compared to erosion and sediment measurements taken after forest thinning and prescribed fire to quantify effects of forest restoration activities. This effort provides unparalleled data on infrastructure, characterization, and research history for climate research and supports partnerships within our national networks that include the National Science Foundation’s National Ecological Observatory Network (NEON), the Southern Sierra Critical Zone Observatory (CZO), and the University of California.

Managing Sierra Nevada forests

There has been widespread interest in applying new forest practices based on concepts presented in the 2009 U.S. Forest Service General Technical Report PSW-GTR-220, "An Ecosystem Management Strategy for Sierran Mixed-Conifer Forests." A new 2012 report (PSW-GTR-237) summarizes the state of the science in topics relevant to this forest management approach, presents case studies of collaborative planning efforts and field implementation of these new practices, and clarifies some of the concepts presented in GTR-220. It also describes a method for assessing forest heterogeneity at the stand level using the Forest Vegetation Simulator and a new geographic information system tool for project level planning that classifies a landscape into different topographic categories. While this collection of papers presents information and applications relevant to implementation, it does not offer standards and prescriptions. Forest management should be flexible to adapt to local forest conditions and stakeholder interests. This report does, however, strive to clarify concepts and present examples that may improve communication with stakeholders and help build common ground for collaborative forest management.

Visit the Ecosystem Function and Health Program pages on our website.