Treesearch

Wildland firefighting is an inherently dangerous activity, and aviation-related accidents in particular comprise a large share of firefighter fatalities. Due to limited understanding of operational factors that lead to aviation accidents, it is unclear how local decisionmakers, responsible for requesting aviation support, can mitigate the risk of an aviation accident once resources are requested. This research expands the knowledge base regarding the quantification and analysis of aerial firefighting exposure by developing methods to evaluate expected aviation accident rates at the...

Wood growth in trees depends on the acquisition of resources, and can vary with tree size leading to a variety of stand dynamics. Typically, larger trees obtain more resources and grow faster than smaller trees, but while light has been addressed more often, few case studies have investigated the contributions of water use and water use efficiency (WUE) within stands to isolate the tree-size dominance effect. Our sites were located near the cities of Aracruz and Eunapolis in Northeastern Brazil. We measured tree biomass growth, water use and WUE to explore patterns of growth among dominant...

The ability of forest resource managers to understand and anticipate landscape-scale change in composition and structure relies upon an adequate characterization of the current forest composition and structure of various patches (or stands), along with the capacity of forest landscape models (FLMs) to predict patterns of growth, succession, and disturbance at multiple scales over time. Comprehensive vegetation maps, which classify patch polygons or raster cells into forest cover types, can be developed from available inventory data (e.g., FIA Grid) in combination with remotely sensed data,...

Effective population size (Ne) is an important parameter in conservation genetics because it quantifies a population's capacity to resist loss of genetic diversity due to inbreeding and drift. The classical approach to estimate Ne from genetic data involves grouping sampled individuals into discretely defined subpopulations assumed to be panmictic. Importantly, this assumption does not capture the continuous nature of populations genetically isolated by distance. Alternative approaches based on Wright's genetic neighborhood concept quantify the local number of breeding individuals (NS) in...

The Aldo Leopold Wilderness Research Institute (ALWRI) was conceived as an interagency partnership, and its founding in 1993 coincided with the creation of the National Biological Service (NBS), from the biological research programs and staff in the Department of the Interior. NBS research zoologist Steve Corn moved to Missoula to join the staff at ALWRI in 1996, at about the same time that NBS was merged into the U.S. Geological Survey (USGS). USGS scientists in Montana were ultimately incorporated into the Northern Rocky Mountain Science Center (NOROCK). Dr. Corn retired in August 2014,...

Atraphaxis has approximately 25 species and a distribution center in Central Asia. It has been previously used to hypothesize an origin from montane forest. We sampled 18 species covering three sections within the genus and sequenced five cpDNA spacers, atpB-rbcL, psbK-psbI, psbAtrnH, rbcL, and trnL-trnF. BEAST was used to reconstruct phylogenetic relationship and time divergences, and S-DIVA and Lagrange were used, based on distribution area and ecotype data, for reconstruction of ancestral areas and events. Our results appear compatible with designation of three taxonomic sections within...

Establishing protection networks to ensure that biodiversity and associated ecosystem services persist under changing environments is a major challenge for conservation planning. The potential consequences of altered climates for the structure and function of ecosystems necessitates new and complementary approaches be incorporated into traditional conservation plans. The conterminous United States of America (CONUS) has an extensive system of protected areas managed by federal agencies, but a comprehensive assessment of how this network represents CONUS climate is lacking. We present a...

Ecological restoration of shrub-steppe communities in the western United States is often hampered by invasion of exotic annual grasses during the process. An important question is how to create restored communities that can better resist reinvasion by these weeds. One hypothesis is that communities comprised of species that are functionally similar to the invader will best resist invasion, while an alternative hypothesis is that structurally more complex and diverse communities will result in more effective competitive exclusion. In this field experiment, we examined the effects of...

A new phytotoxic sesquiterpenoid penta-2,4- dienoic acid, named pyrenophoric acid, was isolated from solid wheat seed culture of Pyrenophora semeniperda, a fungal pathogen proposed as a mycoherbicide for biocontrol of cheatgrass (Bromus tectorum) and other annual bromes. These bromes are serious weeds in winter cereals and also on temperate semiarid rangelands. Pyrenophoric acid was characterized as (2Z,4E)-5-[(7S,9S,10R,12R)-3,4-dihydroxy- 2,2,6-trimethylcyclohexyl)]-3-methylpenta-2,4-dienoic acid by spectroscopic and chemical methods. The relative stereochemistry of pyrenophoric acid was...

Bromus tectorum (cheatgrass, downy brome) is an important invader in western North America, dominating millions of hectares of former semi-arid shrubland. Stand failure or 'die-off' is relatively common in monocultures of this annual grass. The study reported here investigated whether soil-borne pathogens could be causal agents in die-offs. Soils from two die-off areas and adjacent B. tectorum stands were used in a glasshouse experiment with sterilised and non-sterilised treatments. Soil sterilisation did not increase emergence, which averaged 80% in both die-off and nondie- off soils....