Treesearch

Southwestern grasslands today share general differences from their pre-Euro-American settlement conditions. With few exceptions, grasslands--whether in the desert, prairie, or mountains--were, prior to non-Indian settlement, more diverse in plant and animal species composition, more productive, more resilient, and better able to absorb the impact of disturbances. Southwestern grasslands today are missing the elements of disturbance regimes that kept them functioning in the prelivestock period. Such interruptions include human activities leading to loss of palatable plant species and...

The growth of forests can be described as a function of the supply of resources, the proportion of resources captured by trees, and the efficiency with which trees use resources to fix carbon dioxide. This function can be modified to explain wood production by subtracting the allocation of biomass to other tissues and to respiration. At the scale of leaves and seconds, rates of net photosynthesis typically show declining marginal gains with increasing rates of light absorption and transpiration. However, these trends may not represent those that occur at the scale of forests and years,...

In 1999, a coarse-scale map of Fire Regime Condition Classes (FRCC) was developed for the conterminous United States (US) to help address contemporary fire management issues and to quantify changes in fuels from historical conditions. This map and its associated data have been incorporated into national policies (National Fire Plan, Forest Health Initiative) and several General Accounting Office (GAO) reports concerning wildfire management issues. While this data layer has been invaluable for approximating changes in fuels conditions on forestlands overtime, it potentially underestimates...

Aspen communities in the western U.S. are considered at risk because of low levels of disturbance and high levels of herbivory by wild and domestic ungulates. There appears to be a trend toward the loss of aspen-dominated stands West-wide. In some cases the loss is caused by succession, with shade-tolerant conifers becoming dominant. On dry sites where aspen is considered to be the climax, deterioration of aspen stands and loss of regeneration may lead to a conversion to sagebrush or grassland. Data from FIA plots, located in stands with an aspen component and covering the range of aspen...

Rising atmospheric CO2 and temperatures are probably altering ecosystem carbon cycling, causing both positive and negative feedbacks to climate. Below-ground processes play a key role in the global carbon (C) cycle because they regulate storage of large quantities of C, and are potentially very sensitive to direct and indirect effects of elevated CO2 and temperature. Soil organic matter pools, roots and associated rhizosphere organisms all have distinct responses to environmental change drivers, although availability of C substrates will regulate all the responses. Elevated CO2 increases C...

Road removal is being used to mitigate the physical and ecological impacts of roads and to restore both public and private lands. Although many federal and state agencies and private landowners have created protocols for road removal and priorities for restoration, research has not kept pace with the rate of removal. Some research has been conducted on hydrologic and geomorphic restoration following road removal, but no studies have directly addressed restoring wildlife habitat. Road removal creates a short-term disturbance which may temporarily increase sediment loss. However, long-term...

The productivity of fast-growing tropical plantations depends, in part, on the ability of trees to obtain and utilize site resources, and the allocation of fixed carbon (C) to wood production. Simulation models can represent these processes and interactions, but the value of these models depends on their ability to improve predictions of stand growth relative to simpler empirical approaches. We evaluated the 3-PG process-based model for simulating the response of Eucalyptus grandis x urophylla to changes in soil fertility and climate. This was done by calibrating the model with a complete...

Herbaceous communities located within forest openings increase plant species diversity of forests in the Knobs Region of Kentucky. Although these grass-dominated communities are protected and managed for rare plant species conservation, it is unclear how soil conditions may delineate the grassland-forest boundary. We compared soil chemical and physical properties and soil nitrogen pools and transformations of three forest openings with those in the surrounding forest and the wooded edge separating the grassland and forest communities. Soil pH, extractable cations, bulk density and silt...

Millions of hectares of Eucalyptus are intensively managed for wood production in the tropics, but little is known about the physiological processes that control growth and their regulation. We examined the main environmental factors controlling growth and resource use across a geographic gradient with clonal E. grandis x urophylla in north-eastern Brazil. Rates of production and resource use were estimated for 14 stands that spanned a four-fold range in production. The supply of water appeared to be the most limiting resource in these fertilized plantations. Above-ground net primary...

The purpose of this pilot study was to record, characterize, and quantify road maintenance activity in Mexican spotted owl (Strix occidentalis lucida) habitat to gauge potential sound level exposure for owls during road maintenance activities. We measured sound levels from three different types of road maintenance equipment (rock crusherlloader, dozerlroller, and grader), from seven distances (30,60, 120, 180,240,320, and 400 m), in two different habitat types (forested and meadow sites) on the Lincoln National Forest, New Mexico, on 22-23 October 2002 to determine how sound varied over...