Treesearch

Seasonal differences in use of food and habitat have been shown for numerous bird species. Especially during winter, when insect food is often at its lowest availability, birds may be unable to secure enough food for survival. In earlier work in the mixed-conifer zone of the western Sierra Nevada (Blodgett Forest, El Dorado County), observers found that many birds significantly increased their relative use of incense-cedar (Calocedrus decurrens [Torr.] Florin.) for foraging in winter as compared to summer. Preliminary examination of cedar showed the presence of one predominant arthropod...

Baseline levels for densities of snags (standing dead trees) wered etermined in undisturbed old-growth stands on the Gasquet Ranger District. Six Riven National Forest, California. Snag species, number, diameter at breast height (d.b.h.), height, cavity type, cavity use, decay class, and snag origin were recorded on 317 plots over a 2-year period. The 2121 snags recorded consisted of Pseudotsuga menziesii (36 percent), Abies concolor (29 perecnt), Abics mgnifica var. sharlemis (7 percent), Pinus lambertiana (4 percent), Chamaecyparis lawsonina (6 percent), hardwoods (10 percent), and other...

Two hydrologic models were adapted to estimate postfire changer in water yield in Pacific Northwest watersheds. The WRENSS version of the simulation model PROSPER is used for hydrologic regimes dominated by rainfall: it calculates water available for streamflow onthe basis of seasonal precipitation and leaf area index. The WRENSS version of the simulation model WATBAL is used for hydrologic regimes dominated by snowfall; it calculates water available for streamflow based on seasonal precipitation, energy aspect and cover density. The PROSPER and WATBAL models estimate large postfire...

Assessing the trade-offs between market and nonmarket products of wildlands poses a major problem fornatural resource planners and managers. Scenic quality is a resource that is not quantifiable in monetary terms. To determine if market values of real estate offering views could define relative dollar values for physical dimensions and objects in views, they were correlated to real estate prices for 13 recreation subdivisions in California wildlands. View variables were related to lot values in each subdivision, but the specific view variables related to value varied greatly among subdivisi...

A process is described for making comparative valuations of a wide range of environmental management activities when the combined social, economic, managerial, and political benefits of some (but not all) of these activities cannot be adequately described in economic terms, and budgetary constraints do not permit funding all activities under consideration. The process accounts for subjective judgment and contains a formal rigorous decision strategy that takes the place of intuition when quantitative and qualitative values of environmental activities need to be evaluated.

Recent measurements indicate significantly enhanced biogenic soil emissions of both nitric oxide (NO) and nitrous oxide (N2O) following surface burning. These enhanced fluxes persisted for at least 6 months following the burn. Simultaneous measurements indicate enhanced levels of exchangeable ammonium in the soil following the burn. Biomass burning is known to be an instantaneous source of NO and N2O resulting from high-temperature combustion. Now we find that biomass burning also results in significantly enhanced biogenic emissions of these gases, which persist for months following the burn.

Increased hunting pressure for export, commencing about 1975, resulted in a serious decline in the populations of the Yap fruit bat (pieropus mariannus yapensis). Factors causing this pressure included an export market in the U.S. Territory of Guam and in Saipan, Commonwealth of the Northern Mariana Islands and increased use of firearms. Research on Yap fruit bat populations generated legislative support for hunting regulations and gun control. As a result, bat populations have increased two to five-fold between 1981 and 1986. Biological, social, and economic considerations pose a challenge...

Traditional exploitation of fruit bats of Yap is limited, however commercial exploitation greatly reduced populations until they were protected indefinitely. There will be continued need to manage this resource. This paper is based on field work conducted while Yap's bats were intensively hunted. Data from field work is augmented with information from literature on other Pteropus to provide an overall picture of the life history of fruit bats for use by Micronesian resource managers. The original data collected on Yap bats suggests that the populations of fruit bats on yap islands and...

Measurements in the plumes from seven forest fires show that the concentrations of NH3 were considerably in excess of ambient values. Calculation of NH3 emissions from the fires, based on the ratio of NH3/CO in the plumes and emissions of CO from biomass burning, suggest that biomass burning may be a significant source of attnospheric NH3.