Lake Tahoe watershed assessment: volume I

Abstract

The United States Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation and marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) This watershed assessment of the Lake Tahoe basin in northern California and Nevada is the first attempt to collate, synthesize, and interpret available scientific information with a comprehensive view toward management and policy outcomes. The seven-chapter report presents new and existing information in subject areas pertinent to policy development and land and resource management in the basin, including environmental history, air quality, watershed dynamics and water quality, biological integrity, and socioeconomic conditions. Key findings report the extent of recent climatic changes, historic accounts of past environmental disturbances, state of our understanding of why the Lake's clarity is declining, significant role that air quality plays in the decline, and an initial nutrient budget for nitrogen and phosphorous that are believed to fuel algae growth. In addition, important new work related to old-growth forests, the risk of wildfire and the conservation of biological diversity in the basin have helped to broaden our perspective of the interrelated nature of the environmental challenge facing the basin. A detailed analysis of institutional arrangements and capacities in the Lake Tahoe basin is presented in the context of environmental decision-making.

Effects of fuel treatments on fire severity in an area of wildland–urban interface, Angora Fire, Lake Tahoe Basin, California

“…In addition, a large proportion of the Lake Tahoe Basin (including much of the Angora Fire area) was heavily logged in the late 19th and early 20th centuries. Together these factors have resulted in increases in tree density, canopy cover, and surface fuels (Murphy and Knopp, 2000;Taylor, 2004), and many areas within the LTB support very high fuel loadings (see below). Over the last two decades, there has been an annual average of 62 fire starts on National Forest System lands within the LTB, with 79% ascribed to humans and 21% to natural ignitions (Murphy et al, 2007).…”

“…At the South Lake Tahoe, CA airport (1900 m, 3 km due east of the Angora Fire perimeter), the January mean minimum temperature is À10.4 8C, the July mean maximum is 23.5 8C; extreme recorded temperatures are À25.9 and 37.3 8C. Precipitation averages 784 mm per year, with 86% of precipitation falling as snow between November and April (Murphy and Knopp, 2000;WRCC, 2008). The Lake Tahoe Basin Management Unit (LTBMU) of the USDA-Forest Service (USFS) manages about 72% (59,800 ha) of the LTB.…”

Change in the forested and developed landscape of the Lake Tahoe basin, California and Nevada, USA, 1940–2002

“…As management strategies in the Lake Tahoe basin begin to reflect the move into the era of restoration and renewal (Murphy, 2000), results from this assessment of landscape change may be used in future studies requiring a dynamic landscape component, allow decision makers to anticipate possible consequences of forest management and policy as it relates to land use, and support the development of policies focused on minimizing these consequences. Furthermore, although we produced the multi-temporal land-use/cover data to fulfill the needs of this study, we consider this study to be the initial application in anticipation of a wide variety of future uses for these data including watershed/water-quality modeling among others.…”

Multi‐temporal ecological analysis of Jeffrey pine beetle outbreak dynamics within the Lake Tahoe Basin

“…From Smith (1994), the best ecological type match was Jeffrey pine/bitterbrush-snowberry/bluegrass. This area had extensive timber extraction activities in the late nineteenth century when majority of stems were harvested with clearcutting activities between 1875 and 1885 (Murphy and Knopp 2000). Almost all trees on the site naturally regenerated post-harvest, and stands were dominated by trees 100-120 years of age.…”

“…Our study area had land-use history that promoted a consistent age class of mature stems (100-120 years or less) that established following extensive harvesting in the mid-1880s and no disease infection was known to occur within the study site (Murphy and Knopp 2000). Therefore, this study area was ideal for assessing drought interactions with different stem diameter sizes as confounding age-related decadence and disease infection factors were held constant.…”