Treesearch

Numerous subcontinental-scale projects have placed significant emphasis on the use of Normalized Difference Vegetation Indices (NDVI's) derived from Advanced Very High Resolution Radiometer (AVHRR) satellite data for vegetation type recognition. In multi-season AVHRR data, overlap of NDVI ranges for vegetation classes may degrade overall classification performance. The preliminary work of this project is presented to illustrate potential differences in vegetative cover discrimination capabilities between original visible and near-infrared (NIR) channels of AVHRR data and NDVI's derived...

A Monte Carlo simulation was used to evaluate the statistical properties of measures of association and the Kappa statistic under double sampling with replacement. Three error matrices representing three levels of classification accuracy of Landsat TM Data consisting of four forest cover types in North Carolina. The overall accuracy of the five indices ranged from 0.35% to 82.1% depending on the number of classes, the level of classification accuracy of satellite imagery, and the simulated sample sizes of reference plots. Statistical criteria used in the evaluation included: percent bias,...

An accuracy assessment method involving double sampling and the multivariate composite estimator has been used to validate the prototype seasonal land cover characteristics database of the conterminous United States. The database consists of 159 land cover classes, classified using time series of 1990 1-km satellite data and augmented with ancillary data including terrain, climate, and ecological definitions. Reference data from more than 2,200 1 km2 plots were independently collected; data included descriptions of dominant land cover types. Validity of the database is presented in terms...

Adaptive management of ecosystems (e.g., Holling 1978, Walters 1986, Everett et al. 1994, Grumbine 1994, Yaffee 1994, Gunderson et al. 1995, Frentz et al. 1995, Montgomery et al. 1995) structures a system in which monitoring iteratively improves the knowledge base and helps refine management plans. This adaptive approach acknowledges that action is necessary or appropriate with imperfect knowledge (Raiffa 1968, Walters 1986, Everett et al. 1994, USDA/FS and DOI/BLM 1994b) and that initial actions can be refined as more information becomes available. Imperfect knowledge is the case in...

The Southern Region USDA Forest Service recently completed the Southern Appalachian Assessment (SAA). The Assessment is a broad scale interagency analysis and sharing of existing information relative to the natural and human resources of the region. The SAA encompasses over 36 million acres extending from Northern Virginia to Northern Alabama. It was clear early in the Assessment that a uniform land cover data layer would be required to support analysis and modeling.

This publication is the result of a half-day symposium, "Ecology, management, and sustainability of western grassland ecosystems" held at The Wildlife Society's First Annual Technical Conference, September 22-26, 1994 in Albuquerque, NM. The purpose of the symposium was to review and synthesize information about the structure, function, and components of steppe and desert grassland ecosystems in the western United States with special emphasis on the ecological roles and requirements of wildlife species. This work, designed to draw attention to some wildlife topics that have been particularl...

Due to economic and political pressures placed on timber production, information from timber inventories needs to be broken down into information on particular value groups, which are groupings based on individual tree characteristics. Thus estimates of totals and variances need to be computed for individual value groups, all value groups combined, and any collection of value groups. A method for reporting these estimates using a variance-covariance matrix is given. This is followed by two examples of the estimation of totals and variances for value groups applied to a population comprising...

Adaptive management uses an experimental approach in the stewardship of our natural resources. This paper advocates the complementary concept of "adaptive monitoring" to observe and evaluate the outcomes of these experiments. Adaptive management acknowledges that decisions must be made in spite of imperfect understanding of their consequences; likewise, adaptive monitoring is designed to accommodate the unknown objectives and technologies of the future. Adaptive monitoring must be extremely flexible to accommodate constant change in natural resources and management paradigms, in addition...

Fire has been an important evolutionary influence in forests, affecting species composition, structure, and functional aspects of forest biology. Restoration of wildland forests of the future will depend in part on restoring fire to an appropriate role in forest ecosystems. This may include the "range of natural variability" or other concepts associated with fire as a disturbance factor. Yet fire on the forested landscape has not been a constant in either space or time. Its frequency, intensity, seasonality, extent, and other characters - collectively know as a fire regime-varied considerab...

Periodic forest, grassland, and shrubland fires are part of the natural environment-as natural and vital as rain, snow, or wind (Heinselman 1978). Evidence of past fires is found in charcoal layers in lakes and bogs, and in the fire-scarred cross sections of trees. Recurring disturbances by fire are essential to the functioning of many ecosystems, termed "fire-dependent," that are found throughout North America (Heinselman 1978). Many examples are available to describe how fire affects the functioning of ecosystems, such as influencing plant succession, fuel accumulations, structure and...