Treesearch

Where female salmon build nests (‘‘redds’’), streambed material is mixed, fine sediment is winnowed, and bed material is moved into a tailspill mound resembling the shape of a dune. Completed redd surfaces are coarser and better sorted than unspawned beds, which is thought to increase redd stability because larger grains are heavier and harder to move, and sorting increases friction angles for mobility. However, spawning also loosens sediment and creates topography that accelerates flow, which can increase particle mobility. We address these factors controlling the relative stability of...

Fire is one of the most important natural disturbance processes in the western United States and ecosystems differ markedly with respect to their ecological and evolutionary relationships with fire. Reference fire regimes in forested ecosystems can be categorized along a gradient ranging from “fuellimited" to ‘‘climate-limited" where the former types are often characterized by frequent, lower-severity wildfires and the latter by infrequent, more severe wildfires. Using spatial data on fire severity from 1984- 2011 and metrics related to fire frequency, we tested how divergence from...

The storage-discharge relationships of 26 watersheds in the inland Pacific Northwest of the United States were analyzed. Four fitting methods were used to obtain the baseflow coefficients: lower envelope, organic correlation, and ordinary and inverse least squares. Several climatic and terrain attributes were evaluated as predictors of baseflow coefficients. Watersheds dominated by basalt and flatter landscapes exhibited the smallest recession time scales (K) (12.5-20.0 days). Greater K values (33.3-66.7 days) were obtained over catchments dominated by metamorphic and sedimentary rocks....

The present study describes natural regeneration on five permanent research plots (PRP) in juvenile growth and development phases (regrowth and advanced growth) in autochthonous beech forests in Broumovské stěny National Nature Reserve located in the Protected Landscape area in the northeast part of Czech Republic. The stands of herb-rich beech forests were studied in the optimum to break-up stage. Natural regeneration was not evenly spaced but rather was clustered. Mean regeneration density ranged from 1,472 to 44,888 recruits per ha. European beech (Fagus sylvatica L.) made up 78.5–98.0%...

Crested wheatgrass (Agropyron cristatum [L] Gaertm) has been seeded on more than 5 million hectares in western North America because it establishes more readily than native bunchgrasses. Currently, there is substantial interest in reestablishing native species in sagebrush steppe, but efforts to reintroduce native grasses into crested wheatgrass stands have been largely unsuccessful, and little is known about the long-term dynamics of crested wheatgrass/native species mixes. We examined the abundance of crested wheatgrass and seven native sagebrush steppe bunchgrasses planted concurrently...

The loss of big sagebrush (Artemisia tridentata Nutt.) on sites disturbed by fire has motivated restoration seeding and planting efforts. However, the resulting sagebrush establishment is often lower than desired, especially in dry areas. Sagebrush establishment may be increased by addressing factors such as seed source and condition or management of the plant community. We assessed initial establishment of seeded sagebrush and four populations of small outplants (from different geographies, climates, and cytotypes) and small sagebrush outplants in an early seral communitywhere mowing,...

Few seed sources of North American forbs are available for revegetation/restoration of degraded western rangelands adapted to annual precipitation zones less than 300mm, and those that are available are mainly wildland collected. The amount of time and resources necessary to make wildland collections in quantity results in high seed prices and variable seed quality, such that forbs have been under-represented in rangeland seeding mixes. We have previously identified western prairie clover (Dalea ornata Douglas ex Hook.), Searls’ prairie clover (Dalea searlsiae A. Gray), and basalt milkvetch...

Three natural-track selected germplasms of Searls’ prairie clover (Dalea searlsiae (A. Gray) Barneby [Fabaceae]) have been released by the USDA’s Agricultural Research Service (ARS) for use in revegetation and restoration of semiarid rangelands in the western US. Searls’ prairie clover is a perennial leguminous forb that is native to Utah, Nevada, Arizona, and California. Data from common-garden and DNA-marker studies were used to develop and document these releases. The ARS Forage and Range Research Laboratory was asked by the USDI Bureau of Land Management (BLM) and Colorado Plateau land...

Fire is a natural disturbance that occurs in most terrestrial ecosystems. It is also a tool that has been used by humans to manage a wide range of natural ecosystems worldwide. Wildland fire covers a spectrum from low severity, localized prescribed fires, to landscape-level high severity wildfires. The Earth is a fire planet whose terrestrial ecosystems have been modified and impacted by fire since the Carboniferous Period, some 300 to 350 million years before the present time. In the Holocene Epoch of the past 10,000 years, humans have played a major role in fire spread across the planet....

The complex topography of the Inland Northwestern United States (58.4 million ha) interacts with soils and a highly variable climate to provide a mosaic of dry and moist mixed conifer forest settings. Approximately 20% of the area is covered by dry forests dominated by Pinus ponderosa, Pseudotsuga menziesii and contains a diversity of lower vegetation ranging from a grass savannah on the less-productive sites to shrub and forb dominated vegetation on the more-productive sites. An estimated 18% of the area is covered by moist mixed conifer forests with some places growing up to 10 different...