Treesearch

Wildfire ecosystems are thought to be self-regulated through pattern–process interactions between ignition frequency and location, and patterns of burned and recovering vegetation. Yet, recent increases in the frequency of large wildfires call into question the application of self-organization theory to landscape resilience. Topography represents a stable bottom-up template upon which fire interacts as both a physical and an ecological process. However, it is unclear how topographic control changes geographically and across spatial scales. We analyzed fire perimeter and topography data...

Cherrybark oak is a highly desirable hardwood species across the southeastern United States. Silvicultural techniques for establishment have been carefully studied, but advances in tree improvement have yet to be realized. Cherrybark oak seedlings of genetically improved and unimproved stock were tested in field plantings in southern Arkansas and in a controlled pot study for root pruning effects. After 2 years, initial growth advantages of improved stock were no longer present; however, improved stock averaged 19 percent higher survival compared with unimproved seedlings. The improved...

Morphological and molecular phylogenetic studies of true morels (Morchella) in North America, the Dominican Republic, Venezuela, Ecuador, and Peru led to the discovery of four undescribed species of Morchella. Two new species in the Elata clade, one from the Dominican Republic, initially distinguished by the informal designation Mel-18, and a newly discovered sister species from northern Arizona, are now recognized. Mel-18 is described as a novel phylogenetically distinct species, M. hispaniolensis. Its sister species from Arizona is described as M. kaibabensis, also recovered as an...

Artificial pollination of black walnut (Juglans nigra L.) is not practical and timber breeders have historically utilized only open-pollinated half-sib families. An alternate approach called "breeding without breeding," consists of genotyping open-pollinated progeny using DNA markers to identify paternal parents and then constructing full-sib families. In 2014, we used 12 SSR markers to genotype 884 open-pollinated half-sib progeny harvested from two clonal orchards containing 206 trees, comprised of 52 elite timber selections. Seed was harvested in 2011 from each of two ramets of 23...

The effects of forest thinning and wood quality on wood decomposition in the mineral soil were investigated in a Chinese pine (Pinus tabuliformis Carriére) plantation in northern China by measuring mass loss and changes in wood properties (carbohydrates, lignin and nitrogen (N) concentrations) in wood stakes of two tree species - loblolly pine (Pinus taeda L.) and trembling aspen (Populus tremuloides Michx.). Stakes were inserted to a 20 cm soil depth in stands with three thinning levels (low, moderate, and heavy) and an unharvested control and removed after 1 year. There were significant...

Water crises - defined as significant declines in water quality and quantity - top the global risks list compiled by the World Economic Forum (2015) that have the greatest potential impacts on society. Vegetation fires are amongst the most hydrologically significant landscape disturbances (Ebel & Mirus, 2014) and affect ~4% of the global vegetated land surface annually (Giglio, Randerson, & van der Werf, 2013). Fire‐prone or fire‐managed ecosystems (forests, grass‐, and peatlands) also provide ~60% of the water supply for the world's 100 largest cities (Martin, 2016). Accordingly, fire is...

Description of thermal regimes in flowing waters is key to understanding physical processes, enhancing predictive abilities, and improving bioassessments. Spatially and temporally sparse data sets, especially in logistically challenging mountain environments, have limited studies on thermal regimes, but inexpensive sensors coupled with crowd-sourced data collection efforts provide efficient means of developing large data sets for robust analyses. Here, thermal regimes are assessed using annual monitoring records compiled from several natural resource agencies in the northwestern United...

Population viability analysis (PVA) uses concepts from theoretical ecology to provide a powerful tool for quantitative estimates of population dynamics and extinction risks. However, conventional statistical PVA requires long-term data from every population of interest, whereas many species of concern exist in multiple isolated populations that are only monitored occasionally. We present a hierarchical multi-population viability analysis model that increases inference power from sparse data by sharing information among populations to assess extinction risks while accounting for incomplete...

Niche theory predicts that when two species exhibit major niche overlap, one will eventually be eliminated through competitive exclusion. Thus, some degree of niche specialization is required to facilitate coexistence. We examined whether two important seed bank pathogens on the invasive winter annual grass Bromus tectorum (cheatgrass, downy brome) exhibit niche specialization. These pathogens utilize seed resources in complementary ways. Pyrenophora semeniperda is specialized to attack dormant seeds. It penetrates directly through the seed coverings. Hyphae ramify first through the...

Digital cameras can provide a consistent view of vegetation phenology at fine spatial and temporal scales that are impractical to collect manually and are currently unobtainable by satellite and most aerial based sensors. This study links greenness indices derived from digital images in a network of rangeland and forested sites in Montana and Idaho to 16-day normalized difference vegetation index (NDVI) from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS). Multiple digital cameras were placed along a transect at each site to increase the observational footprint and correlation...