Treesearch

Pelletized western redcedar (Thuja plicata Donn ex D. Don) and red alder (Alnus rubra Bong.) seeds exhibited lower total germination and delayed germination speed (G50 or days to 50% germination) when compared to non-pelletized “raw” seeds in greenhouse trials. Averaged across two lots of western redcedar, pelletizing decreased total germination from 81% to 76% and delayed germination by 2 days. Averaged across four lots of red alder, pelletizing decreased germination from 78% to 68% and delayed germination by 7 days. It is logistically difficult to both stratify and pelletize seeds....

Coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings, when planted in a reforestation setting, exhibit early height and diameter growth that is inversely proportional to planting density. One hypothesis to explain this observation is that they are able to detect the presence of nearby trees using phytochrome by sensing the ratio of red to far red light (R/FR) reflected from their crowns. This provides an “early warning signal” of future competition. This signal then triggers a change in growth rate or allometry, which leads to greater height and diameter growth as trees...

Wildland fires are expected to become more frequent and severe in many ecosystems, potentially posing a threat to many sensitive species. We evaluated the effects of a large, stand-replacement wildfire on three species of pond-breeding amphibians by estimating changes in occupancy of breeding sites during the three years before and after the fire burned 42 of 83 previously surveyed wetlands. Annual occupancy and colonization for each species was estimated using recently developed models that incorporate detection probabilities to provide unbiased parameter estimates. We did not find...

Native fishes often face simultaneous threats from habitat fragmentation and invasion by nonnative trout. Unfortunately, management actions to address one may create or exacerbate the other. A consistent decision process would include a systematic analysis of when and where intentional use or removal of barriers is most appropriate. We developed a Bayesian belief network (BBN) as a tool for such analyses. We focused on native westslope cutthroat trout (Oncorhynchus clarkii lewisi) and nonnative brook trout (Salvelinus fontinalis). We considered the environmental factors influencing them,...

Available models of solute transport in heterogeneous formations lack in providing complete characterization of the predicted concentration. This is a serious drawback especially in risk analysis where confidence intervals and probability of exceeding threshold values are required. Our contribution to fill this gap of knowledge is a probability distribution model for the local concentration of conservative tracers migrating in heterogeneous aquifers. Our model accounts for dilution, mechanical mixing within the sampling volume and spreading due to formation heterogeneity. It is developed...

For many reasons, a significant percentage of Alaska’s wildlands have been successfully protected. The passage of the Alaska National Interest Lands Conservation Act (ANILCA), in particular, represents one of the greatest land protection measures in human history. Numerous important factors have contributed to Alaska’s conservation successes, and many of these factors can be used by other nations in achieving and sustaining wilderness areas throughout the world. As in other places, however, Alaska’s natural lands and waters face multiple threats and challenges. If we are to continue to...

Seedling quality and subsequent field performance can be influenced by various stress factors. Measuring seedling quality can help to identify possible crop problems in order to make informed decisions for culturing, lifting, storing, and planting. In addition, seedling quality data can help seedling growers and users to better understand annual patterns among species, stocktypes, seed lots, and cultural treatments. This paper describes stresses that can reduce seedling quality and summarizes several common morphological and physiological measurements that have been linked to seedling...

Ponderosa pine stands were partially cut to various stocking levels at five locations, periodically surveyed, and remeasured during the 20 years after installation. Mean diameter generally increased 2 inches over the 20-year period on most partially cut plots and less than 2 inches on unmanaged controls. Average diameter growth for diameter classes in partially cut plots was generally significantly greater than average diameter growth for the same diameter classes in uncut control plots. Basal area increased 20 to 40 ft2/acre in partially cut plots and 5 to 21 ft2/acre in unmanaged...

Perhaps no plant evokes a common vision of the semi-arid landscapes of western North America as do the sagebrushes. A collective term, sagebrush is applied to shrubby members of the mostly herbaceous genus, Artemisia L. More precisely, the moniker is usually restricted to members of subgenus Tridentatae, a collection of some 20 woody taxa endemic to North America (Beetle 1960; McArthur 1979; McArthur and Plummer 1978). As a group, the Tridentatae are distinguished from other members of the genus by a combination of traits including their woody habit, floral morphology, stem anatomy, plant...

The vegetation, fire regime, and Fire Regime Condition Class descriptions in this paper apply broadly to the Mojave Desert, Colorado Plateau, and southern Great Basin of western North America. More detail on these topics, including estimated percentages within each condition class, is provided for the Mojave-Colorado Plateau ecotone spanning southern Nevada, the Arizona Strip northwest of the Grand Canyon, and southwestern Utah, including the area within the boundaries of the Southern Utah Fuel Management Demonstration Project (Hood and others). Fire Regime Condition Classes (FRCC) are an...