Treesearch

Isoprene is emitted from vegetation to the atmosphere in significant quantities, and it plays an important role in the reactions that control tropospheric oxidant concentrations. As future climatic and land-cover changes occur, the spatial and temporal variations, as well as the magnitude of these biogenic isoprene emissions, are expected to change. This paper presents a study of the change in biogenic isoprene emissions that would result from both anthropogenic land-cover and climate-driven changes. Annual global isoprene emissions were estimated to be 522 Tg yr-1 under current climatologi...

Douglas-fir trees from 39 open-pollinated families at four test locations were assessed to estimate heritability of modulus of elasticity (MOE) and basic density. Heritability estimates of MOE (across-site h

Stand structure and downed woody fuel mass were measured in four replicate units for each of three treatments (unlogged control, commercial harvest, and fuel reduction harvest) following the 1996 Summit Wildfire in northeastern Oregon. Commercial and fuel-reduction harvest resulted in a significant decrease in tree density and tree basal areas. The total downed woody fuel mass significantly increased as compared to the unlogged controls. Model projections of the fuel bed using the Forest Vegetation Simulator indicated the significant difference in downed fuel loading between the unlogged...

Spring-flushing, over-wintered buds of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) produce new buds that may follow various developmental pathways. These include second flushing in early summer or dormancy before flushing during the following spring. Second flushing usually entails an initial release of apical dominance as some of the current-season upper lateral buds grow out. Four hypotheses concerning control of current bud outgrowth in spring-flushing shoots were tested: (1) apically derived auxin in the terminal spring-flushing shoot suppresses lateral bud outgrowth (second...

We incorporated soil/plant biophysical properties into a simple model to predict seasonal trajectories of hydraulic redistribution (HR). We measured soil water content, water potential root conductivity, and climate across multiple years in two old-growth coniferous forests. The HR variability within sites (0 to 0.5 mm/d) was linked to spatial patterns of roots, soil moisture, and climate. The HR seasonally accounted for up to 9 percent of daily water use, peaking at 0.16 mm/d (ponderosa pine) or 0.30 mm/d(Douglas-fir), then declining as modeled pathway conductance dropped with increasing...

Forest environmental conditions are affected by climate change, but investments in forest environmental quality can be used as part of the climate change mitigation strategy. A key question involving the potential use of forests to store more carbon as part of climate change mitigation is the impact of forest investments on the timing and quantity of forest volumes that affect carbon storage. Using an economic optimization model, we project levels of U.S. forest volumes as indicators of carbon storage for a wide range of private forest investment scenarios. Results show that economic...

The purpose of this note is to provide a starting point for discussion of fire hazard reduction treatments that meet the full range of management objectives, including budget priorities. Thoughtful design requires an understanding not only of the physical and biological outcomes, but also the costs and potential revenues of applying variations of fire hazard reduction treatments in a wide range of stand conditions. This analysis was done with My Fuel Treatment Planner software and provides estimates of cost and net revenue from fire hazard reduction treatments on 18 dry forest stands from...

Providing habitat for pileated woodpeckers in the Pacific Northwest has been a key component of forest management strategies for over 20 years. We investigated the diet of pileated woodpeckers, and selection by birds of both individual structure and site characteristics for foraging. Birds foraged amost exclusively in closed-canopy habitats and selected relatively tall, large-diameter snags in early to moderate stages of decay. Sites used for foraging had greater densities of large snags (>51 cm d.b.h. and >7.4 m tall) than sites that were not used. Contrary to previous studies, this study...

Six of nine nonnative boreal conifers in three genera (Abies, Larix, and Pinus) regenerated in 11 to 31 years after they were introduced to mainland Alaska. Lodgepole pine (Pinus contorta var. latifolia Engel.) and the Siberian larches (Larix sibirica Ledeb. and L. sukaczewii N. Dyl.) were the most widely introduced species and will likely be the first nonnative conifers to naturalize. Siberian larch grew up to six times more stem volume than white spruce in the first 40 years on upland sites, but was susceptible to the larch sawfly and a blue stain pathogen carried by bark beetles. On...

Effects of population density of mule deer Odocoileus hemionus on forage selection were investigated by comparing diet characteristics of two subpopulations of deer in southern California, USA, that differed in population density during winter. Quality of diet for deer, as indexed by faecal crude protein, was higher at the low-density site than at the high-density site in winter, when deer densities were different. Quality of diet was similar in summer when both areas had comparable densities of deer. Both outcomes are consistent with predictions from density-dependent selection of diets...