Treesearch

Snags are important to forests because they contribute to the developinent, maintenance, and productivity of' soils and provide habitat for an array of life fornls. Historically, fire has played an irnportant role in shaping the composition and structure of many forests in the western IJnited States and fire is now being reintroduced to restore the natural process. However, the effect of firc: on the snag resource is not well known and responses may differ depending on the length of time between fires. Preliminary data from two frres in eastside pine forests, burning after a long fire-fiee...

Human development appears to present a larger threat to the long-term persistence of California's hardwood rangelands than fire in terms of likely ecological significance. This paper describes of the California Department of Forestry and Fire Protection's Fire and Resource Assessment Program (FRAP) projections of human development and fire occurrence and explores trends in the incidence of fire and development on woodland areas historically dominated by oak species. Previous FRAP work on fire probability on about 3 million acres of private lands in the northwestern Sierra Nevada foothills...

Ecosystem management aligns different uses of the land with ecological parameters and goals of environmental quality. An important USDA Forest Service mission is to balance the multiple uses of its lands in an ecologically sustainable way. This objective has been particularly challenging for National Forests of the Sierra Nevada in the face of heated controversies over the effects of even-aged timber harvest on old-growth forests and their associated wildlife, such as the California spotted owl (Strix occidentalis occidentalis). Much of the concern stems from loss of habitat attributes—clos...

We compared genetic diversity estimated from allozymes and from random amplified polymorphic DNA (RAPDs) in a sample of 210 Great Basin bristlecone pines (Pinus longaeva Bailey) from three groves in the White Mountains, California, USA. The White Mountains are the most westerly extension of bristlecone pine and home to the oldest known living trees. We assayed two forks of each tree to determine whether they originated from multiple seed caches of the Clark’s nutcracker. Despite the limited and fragmented distribution of bristlecone pine, its level of genetic diversity was comparable to...

Measurement of ionic deposition in throughfall is a widely used method for measuring deposition inputs to the forest floor. Many studies have been published, providing a large database of throughfall deposition inputs to forests. However, throughfall collection and analysis is labor intensive and expensive because of the large number of replicate collectors needed and because sample collection and chemical analyses are required on a stochastic precipitation eventbased schedule. Therefore we developed and tested a throughfall collector system using a mixed bed ion exchange resin column. We...

Mexican spruce (Picea mexicana Martínez), an endangered species of the highest sky islands in México’s Sierra Madre Oriental and Sierra Madre Occidental, is threatened by fire, grazing, and global warming. Its conservation depends on whether it also is threatened by inbreeding and loss of genic diversity. We used 18 isozyme markers in 12 enzyme systems to assay genic diversity, characterize the mating system, and test for recent bottlenecks in three known populations. Unbiased, expected heterozygosity (He) averaged 0.125. Despite a separation of 676 km between populations in the Sierra...

Detailed analysis of mixed-conifer and red fir forests were made from extensive, large vegetation sampling, systematically conducted throughout the Teakettle Experimental Forest. Mixed conifer is characterized by distinct patch conditions of closed-canopy tree clusters, persistent gaps and shrub thickets. This heterogeneous spatial structure provides contrasting microclimate, habitat and resource conditions probably associated with the high diversity of understory plants, fungi, and invertebrates found in ongoing studies in the Tea-kettle Experiment. In contrast, red fir forests are more...

Controls on pool formation are examined in gravel- and cobble-bed rivers in forest mountain drainage basins of northern California, southern Oregon, and southeastern Alaska. We demonstrate that the majority of pools at our study sites are formed by flow obstructions and that pool geometry and frequency largely depend on obstruction characteristics (size, type, and frequency). However, the effectiveness of obstructions to induce scour also depends on channel characteristics, such as channel gradient, width:depth ratio, relative submergence (ratio of flow depth to grain size), and the...

Incision of tributaries to Caspar Creek, a gaged Coast Range watershed in Northern California, appears to be an ongoing process that may account for a significant sediment output.