Treesearch

Two methods of estimating the proportion of self-fertilization as opposed to outcrossing in plant populations are described. The first method makes use of marker loci one at a time; the second method makes use of multiple marker loci simultaneously. Comparisons of the estimates of proportions of selfing and outcrossing obtained using the two methods are shown to yield additional information about inbreeding and the genetic structure of populations. Single-locus estimates of the proportion of selfing in Douglas-fir were heterogeneous over marker loci and lower than estimates obtained with...

These 10 symposium papers discuss gene resource management, basic genetics, genetic variation between and within tree species, genetic variability and growth, comparisons of tree life history characteristics, genetic variation in forest insects, breeding systems, and applied uses of isozymes in breeding programs.

Prescribed burning is frequently suggested for reducing conflagration costs in chaparral. Preparation for a prescribed burn includes environmental impact reports, approval by higher levels of authority, and a burn plan. After objectives are stated, the prescription can be written. Elements of the burn prescription reflect fuel, weather, and other factors that determine fire behavior. Proportion of dead fuel, quantity of available fuel, live fuel moisture, topographic features, and chemical content can ail be considered prior to the burn date. Then the desired ranges of dead fuel moisture,...

For each of three species, quaking aspen, ponderosa pine, and lodgepole pine, we determined the relationships between a ranking of heterozygosity of individuals and measures of growth rate. Genetic variation was assayed by starch gel electrophoresis of enzymes. Growth rates were characterized by the mean, standard deviation, logarithm of the variance, and coefficient of variation of annual ring widths measured from cores. In aspen, heterozygosity was associated with high mean growth rate, but in ponderosa and lodgepole pines heterozygosity was not associated with mean growth rate. High...

In a previous study, levels of genetic variation, as measured by isozyme analyses, were compared for 113 taxa of vascular plants. Each species was classified for 12 life history and ecological traits and three measures of genetic variation were calculated. Plants with large ranges, high fecundities, an outcrossing mode of reproduction, wind pollination, a long generation time, and from habitats representing later stages of succession tended to have more isozyme variation than species with other combinations of characteristics. This paper discusses the results of the previous study and...

Electrophoretic techniques permit population biologists to analyze genetic structure of natural populations by using large numbers of allozyme loci. Several methods of analysis have been applied to allozyme data, including chi-square contingency tests, F-statistics, and genetic distance. This paper compares such statistics for pitch pine (Pinus rigida Mill.) with those gathered for other plants and animals. On the basis of these comparisons, we conclude that pitch pine shows significant differentiation across its range, but appears to be less differentiated than many other organisms. Data...

Current knowledge of erosional processes in mountainous watersheds is reviewed with emphasis on the west coast of the United States. Appreciation of the relative magnitude of erosional processes may be distorted by the tendency for researchers to study ""problems"" and by the relatively short time span of their records

Plant roots can contribute significantly to the stability of steep slopes. They can anchor through the soil mass into fractures in bedrock, can cross zones of weakness to more stable soil, and can provide interlocking long fibrous binders within a weak soil mass. In deep soil, anchoring to bedrock becomes negligible, and lateral reinforcement predominates