Treesearch

Progenies of nine ponderosa pines native to one granitic and several ultramafic soils in the northern Sierra Nevada were grown on both soil types in a greenhouse. The progenies differed markedly in first-year growth on infertile ultramafic soils, but not on a fertile granitic soil. Growth differences between progenies were primarily related to differences in calcium uptake from soils low in available calcium. On an extremely infertile ultramafic soil, progenies differed in survival. The results suggest that some ponderosa pines are better adapted than others to the nutritional conditions...

White fir and red fir seed collected over a 2-month period in northern California was tested for germination of fresh and stratified seed. Ratio of embryo length to embryo cavity length was found to be the most useful index of seed maturity for white and red fir. Cone specific gravity also was correlated with nearly all measures of seed germination. Data suggest that red fir cones should be collected as close to beginning of seed fall as possible. White fir cones should be collected within 3½ weeks of seed fall. White fir cones collected 4 weeks before seed fall can be artificially...

The data necessary for fire simulation may be made available through an algorithm based on tracing of boundaries composed of straight-line segments. Useful assumptions are that if a closed boundary does not contain a given point, then any other closed boundary contained within the former one does not contain the location; and that a given location will be contained in a closed boundary if the number of intersections of a finite line segment, drawn from the location to a known point inside the closed boundary, is even. The method described is similar in accuracy to existing alternative...

Control of solar light and heat to develop the proper growth environment is a desirable goal in forest management. The amount of sunlight and heat reaching the surface is affected by shadows cast by nearby objects, including trees. In timbered areas, the type of forest management practiced can help develop desired microclimates. The results depend on the size and orientation of openings created and on the shade cast by surrounding vegetation. A computerized method to calculate the extent of boundary shading for any combination of date, slope, and aspect between 23.45° N. latitude and 50°...

Koa is Hawaii's finest native timber tree. Unfortunately, it grows best in areas that can be converted into good grazing land, and most of the best koa forests have been cleared to develop pasture. Consequently, not much koa is left. Koa seedlings are also palatable to grazing animals, so that the number of young, vigorous koa trees is small.

To convert old-growth redwood (Sequoia sempervirens) to younger managed stands, three types of regeneration cuttings are being tried at the Redwood Experimental Forest, northern California: clearcutting, shelterwood, and selection cutting. Logging mortality was heavy for all tree sizes and greatest where the heaviest cuts were made. The large size of a negative net growth of sawtimber on selection cuttings is attributed to mortality during a 10-year postlogging period. Net growth was slightly negative on shelterwood cuttings. By the end of the 10 years, basal area growth for saplings on...

Ten species of Mexican pines were planted on adverse sites at 6450 feet (1970 m) elevation on Maui, and five species on similar sites at 3200 feet (975 m) elevation on Molokai, Hawaii. Initial survival was poor because of the low quality of the planting stock and harsh site conditions, but subsequent mortality was low. Growth and vigor has been satisfactory. Average annual height growth five years after outplanting ranged from 1 to 3 feet 0.3 to 1 m) on Maui and from 1 to 2 feet (0.3 to 0.6 m) on Molokai. Most trees showed good vigor. The results suggest that Mexican pines would be...

A dynamic fuel model for the chaparral brush fields of southern California shows that (a) the fire threat for the first few years after a fire primarily is related to forbs and grasses; and (b) after 10 to 20 years, the brush fields will sustain very fast-spreading, high-intensity fires, depending upon the ratio of the live-to-dead fuel. The mathematical models described permit systematic analysis of the consequences of fuel treatment and fire control and projection of these consequences for the future.