Treesearch

The relationship between topography and biodiversity is well documented in the Madrean Archipelago. However, despite this recognition, most biogeographical studies concerning the role of topography have relied primarily on a qualitative description of the landscape. Using an algorithm that operates on a high-resolution digital elevation model we present a quantitative analysis of the topographic fabric in the Madrean Archipelago and explored its utility by evaluating a topography-based predicted biodiversity map. In general, we find excellent agreement between the predicted and observed...

The Pennsylvania Department of Conservation and Natural Resources Penn Nursery, located in Spring Mills, PA, was 1 of 4 nurseries participating in a study to determine the effect of acorn sizing on production of northern red oak (Quercus rubra L.) and white oak (Q. alba L.). It is hypothesized that larger acorns would produce larger seedlings. Therefore, by sizing acorns, it will be possible to produce more uniform beds of seedlings, tailor production schedules to acorn size, and reduce cull percentages.Individual papers from this publication

Widespread mortality in the pinyon-juniper forest type is associated with several years of drought in the southwestern United States. A complex of drought, insects, and disease is responsible for pinyon mortality rates approaching 100% in some areas, while other areas have experienced little or no mortality. Implementation of the Forest Inventory and Analysis (FIA) annual inventory in several states coincided with the onset of elevated mortality rates. Adjunct inventories provided supplemental data on damaging agents. Preliminary analysis reveals the status and trends of mortality in...

We developed a density management diagram (DMD) for ponderosa pine using Forest Inventory and Analysis (FIA) data. Analysis plots were drawn from all FIA plots in the western United States on which ponderosa pine occurred. A total of 766 plots met the criteria for analysis. Selection criteria were for purity, defined as ponderosa pine basal area 80% of plot basal area, and even-agedness, as defined by a ratio between two calculations of stand density index. The DMD is relatively unbiased by geographic area and therefore should be applicable throughout the range of ponderosa pine. The DMD...

Over the years, humans have modified the Sonoran Desert by introducing invasive plants that prosper in disturbed and non-disturbed habitats. These invaders modify the dynamics and structure of populations and the composition of communities, which in turn can result in radical changes in wildlife habitat. The natural landscape of the Sonoran Desert is characterized by extensive valleys with parallel and discontinuous arrangements of narrow ranges (Shreve and Wiggins, 1964). Within this ecosystem is the heart of the Sonoran Desert called the Pinacate Reserve (Reserva de la Biosfera El...

Cougars (Puma concolor) and bobcats (Lynx rufus) are present throughout the Sky Islands of the Sonoran desert. We determined the abundance and food habits in northeastern Sonora, Mexico. Abundance indicated that cougars were common (4.19±5.57 cougars/100 km2 and 0.05±0.05 scats/km). According to the scat index, bobcats were more abundant than cougars but no significant differences were found between the two ranches in the study area for both species. Cougars fed primarily on white-tailed deer (Odocoileus virginianus) and bobcats fed primarily on eastern cotton-tailed rabbit (Sylvilagus...

The arid and semiarid regions of Northern Mexico harbor diverse, highly endemic, and geographically complex ecosystems. These share topographic and biogeographic similarities that can be used as an analytical framework to assess biodiversity patterns. This study presents the current status of vascular plant inventories for Mexican Aridamerica. The spatial distribution of floristic records obtained for different vegetation types was analyzed for a 171-year period of field inventories. Floristic curatorial records (96,302) were obtained from the Mexican National Biodiversity Information...

Oak ecosystems of the Southwestern United States are important habitats for a variety of wildlife species. Information is available on the abundance and habitat preferences of some species inhabiting the more densely structured oak woodlands, but little information is available on these topics for the comparatively open oak savannas. Studies are underway to alleviate this situation by determining the abundance of wildlife species commonly found in the oak savannas, identifying the habitat preferences of these species, and assessing the impacts of prescribed burning on the wildlife species....

The relative importance of different factors in driving ecological change in the valleys of southeastern Arizona and southwestern New Mexico has been debated for decades. Clearly, both anthropogenic and natural drivers have played roles: the focus should be on their interactions over time. I suggest that historically, debt and government policies interacted with periodic drought to cause degradation related to livestock. More recently, however, different interactions have emerged. Climate dominates over livestock because stocking rates have declined to relatively low levels, and the...

Fire in semi-arid grasslands releases nutrients bound up in organic matter and accelerates the rate of decomposition in the soil. This research experimentally tested effects of season and frequency of fire on nutrient cycling dynamics in shortgrass steppe. The objective was to identify if fire treatments have the ability to increase potential grassland productivity relative to untreated ëreference conditioní grassland. Many such studies focus on short-term, direct effects of fire. However, this study is part of a long-term, 18-year study examining both direct, and indirect effects of fire...