Treesearch

Generalist pathogens can exhibit differential success on different hosts, resulting in complex host range patterns. Several factors operate to reduce realized host range relative to potential host range, particularly under field conditions. We explored factors influencing host range of the naturally occurring generalist ascomycete grass seed pathogen Pyrenophora semeniperda. We measured potential host range in laboratory experiments at high inoculumloadswith 26 grass species, including the primary host Bromus tectorum, and developed models to predict susceptibility and tolerance based on...

In this issue of the GSD Update, we take a look back at selected studies of the Grassland, Shrubland and Desert Ecosystems Science Program (GSD) that depict its strengths and focus areas. Significant results of recent research and science delivery by GSD scientists are highlighted. We feature program research that lines up with the strategic research priorities of the USDA Forest Service and the Rocky Mountain Research Station (RMRS).

The objective is to evaluate procedures for direct measurement of fire spread rates (FSRs) based on archived repeat pass airborne thermal infrared (ATIR) imagery and to identify requirements for more refined measurements of FSR and environmental factors that influence FSR. Flaming front positions are delineated on sequential FireMapper ATIR images captured at relatively short repeat intervals enabling fire spread vectors and units to also be delineated. This approach provides the only means for estimating FSR for wildfires at spatial scales in the order of 101–103 m and timescales from 102...

The Kirtland’s Warbler (Setophaga kirtlandii), one of the rarest songbirds in North America, was first discovered when Charles Pease shot a migrant on 13 May 1851 on the farm of his father-in-law, Jared P. Kirtland, near Cleveland, OH. The new species was identified by Spencer Baird, who named it for the renowned Ohio naturalist (Baird 1852). The species’ wintering grounds were discovered as additional specimens were collected from throughout the Bahamas, but it took 52 years before Norman Woods followed the lead of a graduate student from the University of Michigan and pursued the species...

Fragmentation poses one of the greatest threats to tropical forests with short-term changes to the structure of forest canopies affecting microclimate, tree mortality, and growth. Yet the long-term effects of fragmentation are poorly understood because (1) most effects require many decades to materialize, but long-term studies are very rare, (2) the effects of edges on forest canopy structure as a function of fragment size are unknown, and (3) edge effects are often confounded by fragment shape. We quantified the long-term (centennial) effects of fragmentation on forest canopy structure...

Species are expected to move uphill or poleward in response to climate change, yet their distributions show idiosyncratic responses; many species are moving in the predicted direction, but others are not shifting at all or are shifting downhill or towards the equator. Fundamental questions remain about the causes of interspecific variation in range responses and whether shifts along elevational and latitudinal gradients are correlated.We examined whether shifts in northernlatitude and upper-elevation boundaries of western North American songbirds over a 35-year period were correlated and...

The early post-disturbance stage of temperate forest succession (also referred to as 'early-seral' or 'early-successional' forest) has been the subject of interest and debate. Often thought of as an ephemeral (and often disorganized) state of eventual closed-canopy systems, its direct and immediate role in conservation traditionally has been ignored except by game biologists. Conservation biologists, until recently, viewed early-seral forest as transitory or a degraded condition of mature or old-growth forest, and, not surprisingly, have studied and promoted management efforts to accelerate...

Population declines of birds that breed in early-successional shrubland habitat are of great concern to conservationists throughout the northeastern United States. To help increase the efficiency and effectiveness of efforts to conserve these species and their habitats, we studied birds in temporary forest openings created through even-aged timber harvest, and permanent wildlife openings maintained through mechanical treatment and prescribed burning in the Northern Appalachians, USA in 2010 and 2011. We assessed the effects of treatment method, time since last treatment, and retained tree...

Many species of mature forest-nesting birds ("forest birds") undergo a pronounced shift in habitat use during the post-fledging period and move from their forest nesting sites into areas of early-successional vegetation. Mortality is high during this period, thus understanding the resource requirements of post-fledging birds has implications for conservation. Efforts to identify predictors of abundance of forest birds in patches of early-successional habitats have so far been equivocal, yet these previous studies have primarily focused on contiguously forested landscapes and the potential...

The potential effects of climate change on net primary productivity (NPP) of U.S. rangelands were evaluated using estimated climate regimes from the A1B, A2 and B2 global change scenarios imposed on the biogeochemical cycling model, Biome-BGC from 2001 to 2100. Temperature, precipitation, vapor pressure deficit, day length, solar radiation, CO2 enrichment and nitrogen deposition were evaluated as drivers of NPP. Across all three scenarios, rangeland NPP increased by 0.26 % year-1 (7 kg C ha-1 year-1) but increases were not apparent until after 2030 and significant regional variation in NPP...