Treesearch

Abstract - The following properties of the Hugo, Mendocino, and Caspar soil series were analyzed at the 10 cm, 20 cm, 30 cm, 50 cm, 100 cm, and 150 cm depths: bulk density; porosity; particle density; saturated and unsaturated hydraulic conductivity; particle-size distribution; pore-size distribution; and water retention characteristics. The Hugo soil series exhibits great variation in its hydrologic properties from location to location. This series differs from the Mendocino and Caspar series by having a higher gravel content, a greater proportion of large diameter pores, and a lower...

Abstract - The most effective control of erosion, in both physical and economic terms, is through prevention because once natural erosion is accelerated, corrective action is not only expensive but seldom entirely successful. To control erosion it is important to understand the forces that cause material to move or resist movement. Once the forces and processes of erosion are understood, proposed erosion control measures can be evaluated for anticipated effectiveness. The successful control of erosion is as much a philosphical and political problem as a technical one

Abstract - Steepland erosion is a composite of surface, channel, and mass erosion. The relative importance of each process is determined by an interaction between climate, soil, geology, topography, and vegetation. A change in any of these components can increase or decrease the rate of erosion. The key to successful management of erosion is the ability to 1) identify potentially erodible sites, 2) correctly assess appropriate activities at those sites, and 3) have a political/regulatory system that allows for the exclusion of hazardous sites from land treatment. Steepland erosion is...

Summary - Vegetation helps stabilize forested slopes by providing root strength and by modifying the saturated soil water regime. Plant roots 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 Mediterranean-type climates, having warm, dry summers, forest evapotranspiration can develop a substantial soil moisture deficit which can reduce both piezometric head and slope mass. Pore water pressures change seasonally in response to precipitation and are often...

Abstract - Stream channel recovery from recent large floods in northern California involves a sequence of processes, including degradation of streambeds to stable levels, narrowing of channels, and accentuation of riffle-pool sequences. Most channels have degraded but remain widened because hillslope encroachment and establishment of riparian groves conducive to sediment deposition have not yet caused streambanks to accrete. The deepening of pools depends on streambed degradation, channel narrowing, and introduction of scouring agents, such as large organic debris, that were removed by...

Abstract - The nature of sediment production from logging roads and the effect of the resulting sediment on salmonid spawning success in the Clearwater River drainage have been studied for eight years. The study includes intensive and extensive analyses of field situations, supplemented by several controlled experiments. It was found that significant amounts (15-25 percent) of fine sediments (less than 0.85 mm diameter material) are accumulaing in spawning gravels of some heavily roaded tributary basins. This accumulation is highest in basins where the road area exceeds 2.5 percent of the...

Abstract - Discharge measurements at nine gauging stations in northern California and southern Oregon document episodes of channel bed aggradation lasting 5 to 15 years after the flood of December 1964 to January 1965. Bed elevations rose 1 to 4 m, then gradually declined to a stable level at or above the pre-flood level. Seven gauging sections widened by 7 to 105 per cent during the aggradation episodes. Channels formed within aggraded material narrowed during degradation; in one case, the pre-flood width was attained. Eroded streambanks formed in non-alluvial material rarely advanced...

Four examples illustrate the potential for practical use of isozyme analyses in applied breeding programs. These include identifying parent trees and clones, seed sources, and parentage of controlled crosses, and evaluating the effectiveness of different procedures involving open-pollination to produce seed of specific crosses. The improved ability to assess the true identity of parents, seed stocks, and controlled crosses justifies the added expense resulting from the use of isozyme analyses in applied tree-breeding programs.

Patterns of genetic variation were studied in three populations of ponderosa pine in Colorado by using electrophoretically variable protein loci. Significant genetic differences were found between separate clusters of trees and between age classes within populations. In addition, data indicate that differential cone production and differential animal damage have genetic components. These results suggest that many diverse phenomena can affect allele frequencies within populations and may contribute to the high levels of genetic variability detected within populations of this species.

Genetic variation at 21 to 25 loci in extracts of individual megagametophytes was surveyed in Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco), Sitka spruce (Picea sitchensis [Bong.] Carr.) and lodgepole pine (Pinus contorta ssp. latifolia [Engelm.] Critchfield). The overall mean proportion of polymorphic loci was 61.19 percent, and the overall mean heterozygosity per individual was 15.81 percent. Sitka spruce was on the low side and interior Douglas-fir on the high side of overall mean genetic variation. Distribution of loci relative to frequency of heterozygotes was rather even for...