Treesearch

Changing fire regimes in western North America have raised the possibility of widespread loss of forest cover, making forest restoration a major priority. In one such ecosystem, the Sierra Nevada in California, the implications of forest management policy have been evaluated primarily via their potential effects on the California Spotted Owl (Strix occidentalis occidentalis). Yet the owl’s cryptic life history, large home range, and declining population all make it difficult to study. The Hermit Warbler (Setophaga occidentalis) may be a valuable proxy species for the Spotted Owl because...

Temporal variability in population growth rates is a fundamental property of natural populations with implications for almost any facet in ecology and evolution. Using the framework of nonlinear averaging, we test the hypothesis that the magnitude of short-term variability in population growth rates is influenced by the long-term means of climatic conditions.

Forest roadside ditch lines capture and redirect road runoff and typically have erosion control treatments installed therein. Existing methods used to determine the effectiveness of roadside ditch line erosion control treatments estimate fixed fractional reductions in sediment yield. However, fixed fractional reductions do not describe dependence on any measurable physical property of treatment, climate, and the environment. Here, we use additional flow roughness induced by erosion control treatments as a metric that can be used as the basis of estimating treatment effectiveness in varying...

Cutleaf daisy has a broad North American distribution (Nesom 2006; USDA 2023). In Canada, it occurs in all territories but Ontario. In the United States, populations occur in Alaska and states from Washington east to the Dakotas and south to Colorado, New Mexico, and California. This species is also thought to occur in Greenland, the Arctic bridge gap (at elevations as low as 30-660 ft [10-200 m]), and in far eastern Russia (Nesom 2006; USDA 2023). Populations of apomictic and sexual plants are segregated, and sexual forms are more common and more broadly distributed than apomictic forms...

Largeflower hawksbeard has a widespread western distribution from British Columbia to Saskatchewan in the north to South Dakota in the east and in New Mexico, Arizona, and California in the south (Hermann 1966; Bogler 2006). Populations are most common in the Columbia Plateau and Great Basin and frequent in northern California and southern Oregon (Babcock and Stebbins 1938; Sears and Whitton 2016). Subspecies occidentalis occurs throughout the species range (Bogler 2006). Subspecies conjuncta occurs in Washington, Montana, Wyoming, Colorado, California, and Oregon. Subspecies costata...

Scabland fleabane occurs in Oregon, Idaho, Nevada, and California, and may occur as far north as central Washington (Cronquist 1947; Munz and Keck 1973; Hickman 1993; Nesom 2006; Hitchcock and Cronquist 2018; USDA NRCS 2023). Variety bloomeri occupies nearly the entire range described for the species (Cronquist 1947; Nesom 2006), while variety nudatus occurs in southwestern Oregon and northwestern California, primarily in the Siskiyou Mountains (Cronquist 1947; Hickman 1993; Nesom 2006).

Snowfall is an important driver of physical and biological processes in alpine systems. Previous work has shown that surface deposition of snow can vary for reasons not directly related to precipitation processes and that this variance has consequence for water budgets in snow-dominated terrestrial systems. In this work, measurements were made over several winter seasons in a forest–meadow ecotone in the Rocky Mountains of southeastern Wyoming. Two groups of measurements - both with wind-exposed and sheltered precipitation gauges - were analyzed. Reasonable agreement between snow deposition...

Basalt milkvetch is one of the most common and widely dispersed Astragalus species (Barneby 1964; Johnson et al. 2008). It occurs in western North America from southern British Columbia to northern Mexico where annual precipitation ranges from 5 to 30 in (127-762 mm) (Tilley et al. 2017). Populations are somewhat isolated in southern British Columbia and disjunct and scattered in the mountains of interior southern California and northern Baja California (Barneby 1964). Populations are widespread and locally abundant in the Columbia Basin and Great Basin (Barneby 1989; Mansfield 2000),...

A function that predicts the upper stem diameters of an individual tree is helpful in better quantifying the volume and devising sustainable management of commercially and ecologically important species. This study compares three forms of the taper equation (single, variable-exponent, and segmented) using destructive sample data collected from 80 Chir pine (Pinus roxburghii Sarg.) trees across three adjacent stands in the Mid hills of Nepal. A mixed-effects modeling approach was used to evaluate the 13 different taper functions, selecting the best parameter association with the random...

Under climate change, ecosystems are experiencing novel drought regimes, often in combination with stressors that reduce resilience and amplify drought’s impacts. Consequently, drought appears increasingly likely to push systems beyond important physiological and ecological thresholds, resulting in substantial changes in ecosystem characteristics persisting long after drought ends (i.e., ecological transformation). In the present article, we clarify how drought can lead to transformation across a wide variety of ecosystems including forests, woodlands, and grasslands. Specifically, we...