Treesearch

Positive correlations between measures of "fitness" and the number of electrophoretic loci for which an individual is heterozygous have been observed in many species. Two major hypotheses have been proposed to explain this phenomenon: inbreeding depression and overdominance. Until recently, there has been no way to distinguish between these hypotheses. The overdominance model devised by Smouse (1986) is used here in a reanalysis of Ledig et al.'s (1983) study of heterozygosity and growth rate in eight populations of pitch pine and is contrasted with an inbreeding-depression analysis. Ledig...

Consideration of cumulative watershed effects (CWEs) has both political and physical aspects. Regardless of the practical usefulness of present methods of dealing with CWEs, the legal requirement to address them remains. Management of federal land is regulated by the National Environmental Policy Act (NEPA) and the Federal Water Pollution Control Act of 1972. The state of California has passed analogous laws: California Environmental Quality Act (CEQA) and the Porter-Cologne Act--both of which affect management on private land, primarily through the Forest Practice Regulations that they...

Readers of this Newsletter are aware that CDF and the USFS, through its Pacific Southwest Forest and Range Experiment Stationa at Arcata (PSW), are carrying out a long term cooperative watershed experiment in JDSF's Caspar Creek drainage.

Abstract - A programmable calculator is connected to a pumping sampler by an interface circuit board. The calculator has a sediment sampling program stored therein and includes a timer to periodically wake up the calculator. Sediment collection is controlled by a Selection At List Time (SALT) scheme in which the probability of taking a sample is proportional to its estimated contribution to total sediment discharge, or according to accumulated predicted sediment weight. Stage height is also measured and is recorded according to a set scheme.

A test of open-pollinated pitch pine families from 17 different locations on the Atlantic Coastal Plain was evaluated at 12 years of age. Genetic variation for growth was almost totally on the provenance level and was detectable among families within provenances in only a few cases. Mean volume decreased with latitude and also with distance of the seed origin from the test site. Provenances with the largest mean volume per tree came from locations 5.3 and 24.8 km distant from the test site and those with the smallest, from 349 and 388 km distant. The frequency of trees with serotinous...

Fire management simulation models are used to predict the impact of changes in the fire management program on fire outcomes. As with all models, the goal is to abstract reality without seriously distorting relationships between variables of interest. One important variable of fire organization performance is the length of time it takes to get suppression units to the fire. Because the location of the fires cannot be predicted and because suppression units are not always available at a particular base location, the types of units sent and their arrival times vary This aspect of fire...

Western dwarf mistletoe (Arceuthobium campylopodum) is a damaging parasite of Jeffrey pines (Pinus jeffreyi) in southern California. Infected branches that develop into brooms are believed to reduce tlee vigor and increase mortality. Brooms were pruned from Jeffrey pines with varying levels of dwarf mistletoe infection and live crown. Many of the trees showed an increase in crown vigor when compared with unpruned trees after 5 years. Mortality was not reduced by pruning brooms, except during years of below-normal precipitation. Of the trees that died, most had little live crown, heavy...

Fire weather stations used to be located only where observers were available. Now, remote automatic weather stations can sample weather without manual assistance, virtually anywhere, Locating them, however, remains a problem. An objective method was developed for designing a fire weather network. The design process begins with the identification of the area to be sampled, the relevant meteorological variables, target meteorological fields, and interpolation (or other analysis) method to be used. Using a least-squares criterion, optimum networks for a varying number of stations are computed...

The usefulness of an analytical model as a fire management decision tool is determined by the correspondence of its descriptive capability to the specific decision context. Fire managers must determine the usefulness of fire models as a decision tool when applied to varied situations. Because the wildland fire phenomenon is complex, analytical fire spread models will have descriptive limitations. Some limitations in the widely used and accepted Rothermel fire spread model are discussed in terms of the model's assumptions and mathematical formulations, in the context of prescribed burning...

The historic Bel Air fire of 1961 was not unusually large or fast-moving, nor was it a disaster for the native chaparral ecosystem. Yet it was disastrous for residents of the area, a consequence of unrestricted urban development in the chaparral of Southern California. Its costs included human suffering and financial loss from the destruction of 484 of 2,300 homes.