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Pacific Southwest Research Station
Tahoe Science Projects supported by SNPLMA
Ecosystem response to aspen restoration
John-Pascal Berrill and Christa Dagley, Humboldt State University
This study will support continued monitoring of one-hectare permanent plots installed in nine conifer-encroached aspen stands around the Tahoe Basin. Thinning of encroaching conifers has been completed at six sites, and should occur in 2012 at the other three sites. This study will allow monitoring to continue for up to five years since restoration thinning and three years since pile burning, giving time to assess ecosystem response. Before thinning, aspen and conifer trees were measured for size and their health status assessed. A total of 3,752 trees have been tagged, mapped, and measured. Post-thinning assessment has been completed in thinned stands, giving number of trees cut and records of damage to the remaining trees. Aspen and conifer regeneration has been quantified pre- and post-thinning. Over 3,000 conifer seedlings and 3,000 aspen suckers have been counted in subplots to analyze regeneration patterns. Existing data shows that thinning intensity differed widely between sites. Between 33% and 82% of trees have been cut, but these were the smaller trees, so 'crowding' (in terms of stand density index) was only reduced by 8% to 63% between sites. Since we measured pre-treatment crowding (indicator of stress) and intensity of thinning, we are able to correlate these with ecosystem response in terms of regeneration, growth, and stem breakage (wind/snow damage). Ecosystem response to pile burning will also be examined. Cut conifer wood, branches, and debris have been piled for burning in small, medium, and large piles. The piles were burned at one site in fall 2011, and damage noted. The products of our study will directly support adaptive management in restoration and inform conservation of aspen communities in a changing climate by describing the biology and ecological processes underlying observed responses to restoration and external factors such as changes in water supply.
Relation to Other Research Including SNPLMA Science Projects
Quaking aspen is considered a keystone species (Shepperd et al., 2006). It is one of only a few broadleaved trees in the Tahoe Basin. Issues such as providing wildlife habitat, aesthetics, water quality, natural firebreaks, and sustaining rich diverse understory plant communities and ecological processes are driving the interest in conserving and restoring aspen stands. Understanding the effects of restoration activities, natural disturbances, and climate change requires rigorous monitoring and scientific inquiry. The research team will continue to collaborate with Lake Tahoe Basin land managers focusing on the monitoring of aspen restoration treatments and will continue to provide updates of the associated scientific inquiry. The proposed research has been designed to build on three existing studies in the Tahoe Basin: 1) SNPLMA Round 9, "Effects of pile burning in the Tahoe Basin on soil and water quality," 2) SNPLMA Round 10, "Stocking guidelines for aspen restoration," and 3) a Forest Service-Lake Tahoe Basin Management Unit (LTBMU)-Humboldt State University monitoring collaboration, "Effects of slash pile burning after restoring conifer-encroached aspen." Monitoring responses to restoration thinning and pile burning will provide all participating agencies with a determination of the effectiveness and success of their restoration treatments.
Expected date of final products:
|Last Modified: Mar 7, 2013 06:28:12 PM|