نتایج جستجو برای: stands
تعداد نتایج: 21645 فیلتر نتایج به سال:
—Widespread establishment of seedling aspen (Populus tremuloides) occurred in Yellowstone National Park (YNP) following the extensive1988 fires. Aspen stands occupy ;2% of YNP and aspen stems are intensively browsed by native ungulates. Chemical composition, especially secondary compounds, may influence levels of herbivory and, hence, survival of aspen, but concentrations of such compounds in a...
The effects of logging on ecosystem sustainability are controversial. Surprisingly, existing data are inadequate to allow a comprehensive evaluation of logging effects on biodiversity, composition, and productivity since appropriate comparisons of stands of similar ages and differing disturbance histories are rare. We addressed this issue using a study of 2000 plots in 80 southern boreal forest...
The effects of three common tree species – Scots pine, Norway spruce and silver birch – on leaching of dissolved organic carbon and dissolved nitrogen were studied in an experimental forest with podzolised soils in southern Sweden. We analyzed soil water collected with lysimeters and modeled water fluxes to estimate dissolved C and N fluxes. Specific UV absorbance (SUVA) was analyzed to get inf...
Defoliation by the European gypsy moth (Lymantria dispar L.) and subsequent tree mortality have been well documented in the northeastern United States. In this study we evaluate tree mortality after initial defoliation in mixed pine-hardwood stands in the southeastern United States as the range of European gypsy moth expands. In 1993, 46 mature pine-oak and pine-sweetgum stands were selected on...
Analysis of Thermal Infrared Multispectral Scanner data collected over H. J. Andrews experimental forest in western Oregon indicated that aspect and slope gradient had a greater effect on the thermal emission of younger reforested clearcuts than of older stands. Older forest stands ( > 25 years) with greater amounts of green biomass and dosed canopies had lower effective radiant temperatures th...
Introduction The rate at which Acacia koa (koa) stands develop has important implications for koa plantation forestry and the use of koa in ecosystem restoration. How quickly individual trees grow, how growth rate changes over time, and how stands self-thin is not well understood. Development of koa stands may differ from that of other trees because koa is a nitrogen-fixing species. Like most l...
Aspen communities in the western U.S. are considered at risk because of low levels of disturbance and high levels of herbivory by wild and domestic ungulates. There appears to be a trend toward the loss of aspen-dominated stands West-wide. In some cases the loss is caused by succession, with shade-tolerant conifers becoming dominant. On dry sites where aspen is considered to be the climax, dete...
We investigated Marbled Murrelet (Brachyramphus marmoratus) habitatuse patterns by censusing a variety of forest stands at Redwood Experimental Forest in northwestern California. Murrelet activity levels were greatest 30 minutes before to 30 minutes after sunrise in May, June, and July. Surveys at fixed stations showed that during the breeding season, murrelets were present more often in old-gr...
We examined the range and the relationships of Marbled Murrelet (Brachyramphus marmoratus) behavior with habitat and landscape characteristics in isolated old-growth and residual forest stands from 2 to 400 ha in California. In large contiguous stands of old-growth forest in parks, we examined relationships of murrelet detections with elevation and topography. In isolated stands we found higher...
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