USDA Forest Service

Pacific Southwest Research Station

Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
United States Department of Agriculture Forest Service. USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.

Restoration and fuel treatment of Lake Tahoe's riparian forests

Old-growth forestsPrincipal Investigator:
Malcolm North, USDA Forest Service-Pacific Southwest Research Station

Proposal [pdf]

Van de Water and North 2010 [pdf]
Van de Water and North 2011 [pdf]

Please contact Dr. Malcolm North with questions regarding the reports.

Project Summary

Fire is an important ecological process in many western U.S. coniferous forests, yet high fuel loads and rural home construction lead to the suppression of most wildfires. Using mechanical thinning and prescribed burning, managers often try to reduce fuels in strategic areas with the highest fuel loads. Riparian forests, however, are often designated as areas where limited management action can take place within a fixed-width zone. These highly productive zones have developed heavy fuel loads capable of supporting stand-replacing crown fires that erode stream channels, eliminate important wildlife habitat and degrade ecosystem function.

The objectives of this study were to determine whether adjacent coniferous riparian and upland forests burned historically with different frequencies and seasonalities, whether they had different stand structures and fuel loadings, and whether the relationship varied by forest type, riparian zone widths, and precipitation regimes. Dendrochronological fire records, current stand structures, and fuel loadings were examined in adjacent riparian and upland sites in three forest types (mixed-conifer, white fi r, Jeffrey pine), two riparian zone widths (broad and narrow), and two precipitation regimes (dry east side and wet west side).

Riparian and upland fire return intervals were significantly different in only one quarter of the sites sampled. Riparian and upland areas did not burn with different seasonalities and fire events occurred primarily during the late summer-early fall dormant season in both riparian and upland areas. Upland areas exhibited a greater degree of fire–climate synchrony than riparian areas. Reconstruction results suggest that historic fuels and forest structure may not have differed significantly between many riparian and upland forests, consistent with earlier research suggesting similar historic fire return intervals.

The study suggests that Sierra Nevada coniferous riparian forests bordering many montane streams might be managed for fuel loads and fire return intervals similar to adjacent upland forests. Under current conditions, however, modeled severity is much greater in riparian forests, suggesting forest habitat and ecosystem function may be more severely impacted by wildfire than in upland forests.