Treesearch

An ecological classification system has been developed for the Pacific Southwest Region of the Forest Service. As part of that classification effort, blue oak (Quercus douglasii) woodlands and forests of southern San Luis Obispo and northern Santa Barbara Counties in Los Padres National Forest were classified into I3 plant communities using vegetation collected from 208 plots, 0.1 acre each. Three distinct regions of vegetation were identified in the study area: Avenales, Miranda Pine Mountain and Branch Mountain. Communities were classified separately for plots in each region. Each region...

A seedling testing program was developed to improve the survival and growth potential of planting stock produced in the USDA Forest Service Humboldt Nursery, situated on the Pacific Coast in northern California. Coastal and inland seed sources of Douglas-fir and eight other conifers in the Pacific Slope forests of western Oregon and northern California were assessed in both nursery and field studies. Seedling top and root growth capacities were evaluated just after lifting and after cold storage, and stored seedlings were tested for survival and growth on cleared planting sites in the seed...

Pinus evolved in middle latitudes of the Northern Hemisphere in the middle Mesozoic. By the late Cretaceous pines had spread east and west throughout Laurasia, attaining high diversity in eastern Asia, the eastern United States, and western Europe, but having little representation at high northern latitudes. Changing climates in the early Tertiary established warm and humid tropical/subtropical conditions in a broad zone to 70°N throughout middle latitudes. Pines and their relatives disappeared from many middle-latitude areas during this time and were replaced by diverse angiosperm taxa of...

An 11-year-old ponderosa pine (Pinus ponderosa Dougl. ex Laws. var. ponderosa) plantation in northern California was grazed annually in summer by 600-1150 dry (nonlactating) ewes in an attempt to reduce competing vegetation and increase growth of pine seedlings. The sheep also provided an opportunity to evaluate density and developmental trends in the pine, shrub, grass, thistle, and forb components of the plant community. A manual release and a deer-only treatment provided contrast to the effects of grazing by sheep. In general, stem diameter and foliar cover of ponderosa pines, rarely...

Conifer productivity in western North America is often severely inhibited by competing vegetation. Abies concolor [Gord. and Glendl.] Lindl. (white fir) is an important species over much of this area, yet little information is available on response of A. concolor to vegetation management treatments. We revisited two sites in the northern Sierra Nevada to assess the responses of naturally regenerated A. concolor saplings to vegetation recovery 8-9 years after release treatments. Treatments caused major and persistent shifts in vegetation structure and composition on both sites. Differences...

Seed source and sowing date effects on first-year seedling growth and Fusarium root and collar rot of sugar pine were analyzed in two consecutive nursery tests at the Pacific Southwest Research Station's Institute of Forest Genetics, near Placerville in the western Sierra Nevada. The experimental design in both tests consisted of four replications of a randomized complete block of split-split plots, with sowing date split for disease treatment and seed source. Seed sources were natural stands at low, middle, and high elevations on the western slope of the northern Sierra Nevada. Seeds were...

In a pollen exclusion experiment performed on the cones of five Douglas-fir (Pseudotsuga menziesii [Mirbel] Franco) trees, the number of seeds infested by a seed chalcid, Megastigmus spermotrophus Wachtl, did not differ significantly between pollinated and unpollinated cones from the same tree. This finding led to a revision of the formula used to calculate M. spermotrophus effect on Douglas-fir seed production because the traditional formula, which is based on the assumption that only pollinated seeds are infested by these chalcids, exaggerates their effect. The relationship between the...

The term piping has been used to describe subsurface erosion processes and concentrated subsurface water discharge. Physical features created by piping have been termed pipes. Piping can occur in natural landscapes due to individual or combined effects of mechanical (e.g., corrasion), chemical (e.g., soil dispersion), or biotic (e.g., animal burrowing) forces normally occurring in subsurface environments.

Abstract - Three zero-order swales, each with a contributing drainage area of about 1 ha, were instrumented to measure pipeflows within the Caspar Creek Experimental Watershed in northwestern California, USA. After two winters of data collection, the second-growth forest on two of the swales was clearcut logged. The third swale remained as an uncut control. After logging, peak pipeflow was about 3.7 times greater than before logging. Before logging, little sediment was transported through the pipes. Suspended sediment concentrations before logging were less than 20 mg l -1 and coarse-graine...