Treesearch

Brush species make up much of the fuel load in forested wildlands. Basic physical and chemical characteristics of these species influence ease of ignition, rate of fire spread, burning time, and fire intensity. Quantitative knowledge of the variations in brush characteristics is essential to progress in fire control and effective use of fire in wildland management. Five shrub species common to northern California brush fuels were analyzed in this study-greenleaf manzanita, snowbrush, mountain whitethorn, chinkapin, and bitter cherry. Quantitative data on ash content, fuel density, solvent...

Flow charts are a widely used means of diagramming relationships among transport processes and storage sites during analyses of sediment routing. Because they have taken so many different forms, however, it is very difficult to use published flow charts to compare geomorphic systems. Though they generally are constructed to achieve the same purpose, flow charts differ in the definition of the material being transported, type of transport processes involved, and the kinds of landscape elements considered to be sediment storage sites

Legislation to regulate forest practices, water quality, and management of federal lands has increased the land managers' need for efficient methods of identifying and mapping sources of sediment in forested basins. At the same time, theoretical analysis of landscape evolution has led research geomorphologists to the consideration of many of the same sedimentation problems as those confronting land managers. This discussion session demonstrated that, although many of the fundamental questions addressed by these groups are identical, the approaches taken in answering those questions differ...

In Japan, landslides are such a major national hazard that in 1958 the ""Landslide Prevention Law"" was passed and an extensive program for research, engineering, and control of landslides has developed. There is no comparable legislative mandate in the United States. Contrary to the situation in Japan where lives and property are jeopardized by landslides, in the U.S. the main concern for controlling landslides is to preserve water quality and timber site productivity. In late summer 1981, a team of six U.S. scientists spent two weeks in Japan under the auspices of the U.S./Japan Science...

Abstract - The additional strength provided by roots to the soil is generally considered to be in the form of a cohesive strength C which may range in magnitude from 1 kPa to 20 kPa. Studies of the tensile strength of tree roots show that small roots sampled from living trees range in mean tensile strength from about 10 MPa to about 60 MPa. After tree felling small roots lose their strength at average rates between 300 and 500 kPa per month. Root biomass also decreases rapidly after clearfelling. The reduction in C after forest removal is a prime cause of landsliding on many steep slopes.

Reported rates at which hand crews construct firelines can vary widely because of differences in fuels, fire and measurement conditions, and fuel resistance-to-control classification schemes. Real-time fire dispatching and fire simulation planning models, however, require accurate estimates of hand crew productivity. Errors in estimating rate of fireline production affect estimates of fire size in simulation models predicting fire suppression effectiveness. Productivity rates, therefore, are crucial for such models and the high variability makes choices difficult. Studies of crews using...

Abstract - A sediment budget for a drainage basin is a quantitative statement of the rates of production, transport, and discharge of detritus. To construct a sediment budget for a drainage basin, one must integrate the temporal and spatial variations of transport and storage processes. This requires: recognition and quantification of transport processes, recognition and quantification of storage elements, and identification of linkages among transport processes and storage elements. To accomplish this task, it is necessary to know the detailed dynamics of transport processes and storage...

A theoretical probability model has been developed for analyzing program alternatives in fire management. It includes submodels or modules for predicting probabilities of fire behavior, fire occurrence, fire suppression, effects of fire on land resources, and financial effects of fire. Generalized "fire management situations" are used to represent actual fire management areas. The model serves as the framework for the Fire Economics Evaluation System now being designed at the Pacific Southwest Forest and Range Experiment Station. Outputs from the model will consist of probability distributi...

This report describes 14 meadow site classes derived through techniques of agglomerative cluster analysis. The class names are: Carex rostrata (beaked sedge), Poa (Kentucky bluegrass), Heleocharis/Heleocharis (ephemeral-lake), Hypericum/Polygonum/ Viola (hillside bog), Trifolium/Muhlenbergia (longstalk clover), Deschampsia/Aster (tufted hairgrass), Carex nebrascensis (Nebraska sedge), Heleocharis/Muhlenbergia (fewflowered spikerush), Muhlenbergia/Heleocharis (pullup muhly), Agrostis (bentgrass), Trifolium/Mimulus (carpet clover), Calamagrostis/Oryzopsis (shorthair), Gentiana/Aster (gentian-...

The Fire Economics Evaluation System (FEES)--a simulation model--is being designed for long-term planning application by all public agencies with wildland fire management responsibilities. A fully operational version of FEES will be capable of estimating the economic efficiency, fire-induced changes in resource outputs, and risk characteristics of a range of fire management program options. Risk is described by the probability distributions of economic efficiency and resource output changes that result from annual variation in factors such as fire occurrences and fire weather. Particular...