Treesearch

To better understand habitat-specific predation risk for stream fish, we used an approach that assumes animals trade off food for safety and accurately assess risk such that predation risk can be measured as a foraging cost: animals demand greater harvest rates to occupy riskier locations.We measured the foraging cost of predation risk for juvenile salmonids within enclosures in a natural stream at locations that varied in water depth and distance to cover. Measurements relied on a food delivery apparatus and direct observations that allowed estimation of "giving-up" harvest rates – food...

Soil compaction is known to limit plant growth by reducing soil macroporosity and restricting gas, water, and root movement. Recent evidence from study sites across the United States and Canada, however, suggests that tree growth is not universally affected by soil compaction from forest harvesting practices. Our observational study examined rooting patterns in mixed conifer plantations in the central Sierra Nevada of California to determine whether tree roots use continuous pathways or channels to overcome the physical restrictions of compacted soil. Replicate plots were established 20‐25...

Forested wetlands dominated by black ash (Fraxinus nigra) are currently threatened by the rapid expansion of the exotic emerald ash borer (EAB) (Agrilus planipennis, Coleoptera: Buprestidae) in North America, and very little is known about the hydrology and ecology of black ash wetlands. The ecohydrological response of forested wetlands following a canopy disturbance has the potential to affect critical ecosystem services, and the degree of this effect may largely depend on the wetland's hydrogeological setting. The main objectives of this study were to characterize the hydrologic connectiv...

Landscape exposure to multiple stressors can pose risks to human health, biodiversity, and ecosystem services. Attempts to study, control, or mitigate these stressors can strain public and private budgets. An interdisciplinary team of Pacific Northwest Research Station and Oregon State University scientists created maps of the conterminous United States that indicate landscape exposure to concentrated wildfire potential, insects and disease risk, urban and exurban development, and climate change. The maps, which show where these stressors might occur and overlap, provide a valuable...

Waterways of the USA are protected under the public trust doctrine, placing responsibility on the state to safeguard public resources for the benefit of current and future generations. This responsibility has led to the development of management standards for lands adjacent to streams. In the state of Oregon, policy protection for riparian areas varies by ownership (e.g., federal, state, or private), land use (e.g., forest, agriculture, rural residential, or urban) and stream attributes, creating varying standards for riparian land-management practices along the stream corridor. Here, we...

In the northeastern United States, tree declines associated with acid deposition induced calcium depletion have been documented, notably for red spruce (Picea rubens Sarg.) and sugar maple (Acer saccharum Marsh.). There is conflicting evidence concerning whether co-occurring tree species capitalized on these declines or suffered similar growth reductions and on how growth has fluctuated relative to environmental variables. We examined five species along three elevational transects on Mt. Mansfield, Vermont: sugar maple, red spruce, red maple (Acer rubrum L.), yellow birch (Betula alleghanie...

To better understand the potential impact of the invasive hemlock woolly adelgid (HWA, Adelges tsugae Annand) and presalvage activities on carbon (C) dynamics in northern stands of eastern hemlock (Tsuga canadensis (L.) Carr.), we used the Forest Vegetation Simulator and Forest Inventory and Analysis data to model C storage and successional pathways under four scenarios: presalvage harvesting; HWA-induced mortality; presalvage harvesting plus HWA-induced mortality; and no disturbance (control). Our simulation showed that all treatments differed in total C storage in the short term, with...

The ultimate goal of any tree improvement program is the large-scale production and distribution of genetically improved seedlings. In black walnut, projections based on earlier research indicate that genetically improved seedlings could provide growth improvement of between 15 to 25 percent by using seed or seedlings of the proper geographic origin (Bey 1980; Clausen 1981; Deneke et al. 1987) and additional gains of similar magnitude from progeny testing (Rink 1984). Unfortunately, the large-scale production of such genetically improved seedlings has yet to become a reality. The purpose...

ContextThe proportion of fire area that experienced stand-replacing fire effects is an important attribute of individual fires and fire regimes in forests, and this metric has been used to group forest types into characteristic fire regimes. However, relying on proportion alone ignores important spatial characteristics of stand-replacing patches, which can have a strong influence on post-fire vegetation dynamics. ObjectivesWe propose a new more ecologically relevant approach for characterizing spatial patterns of stand-replacing patches to account for potential limitation of conifer seed...

Population genetic information can provide valuable insight for the conservation and management of threatened and endangered plant species. Tamarix taklamakanensis is an endangered shrub endemic to arid basins of northwestern China. This species serves to stabilize soils in this region, but has seen substantial loss in its abundance due to depletion of ground water. The populations of this species have become small and fragmented, warranting conservation. Seven microsatellite loci were used to assess the genetic diversity and structure of 15 populations in the Tarim Basin, China. Among...