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The term “landscape structure” refers to the configuration of vegetation and other land features over a large land area (usually an extent of many square kilometers). A landscape can be regarded as a mosaic composed of patches of different kinds -- for example, different forest types, landforms, or human-built structures such as roads. The scientific discipline of landscape ecology is concerned with quantitatively describing the features of landscape mosaics, including, for example, the variety of patch types, the sizes and shapes of patches, and how different patch types are juxtaposed...

The impact of construction of dams and reservoirs on alluvial rivers extends both upstream and downstream of the dam. Downstream of dams, both the water and sediment supplies can be altered leading to adjustments in the river channel geometry and ensuing changes in riparian and aquatic habitats. The wealth of pre and post-regulation data on the Middle Rio Grande, New Mexico, provides an excellent case study of river regulation, channel adjustments, and restoration efforts. Cochiti Dam was constructed on the main stem of the Rio Grande in 1973 for flood control and sediment retention. Prior...

We compared two methods of detecting presence of swift fox: smoked-plate scent stations and spotlight counts. Tracks were counted on ten 1-mile (1.6-km) transects with bait/tracking plate stations every 0.1 mile (0.16 km). Vehicle spotlight counts were conducted on the same transects. Methods were compared with Spearman's rank order correlation. Repeated measures analysis of variance was used to test the null hypothesis that there were no differences between months or between days that track and spotlight counts were conducted. We also evaluated optimum spacing of tracking plates by...

Landscape-scale fire patterns result from complex interactions among weather, ignition sources, vegetation type and the biophysical environment (Hargrove et al. 2000, Morgan et al. 2001, Keane et al. 2002, Hudak, Fairbanks & Brockett in press). Patch characteristics (e.g. woody canopy cover) influence fire characteristics, which in turn influence patch characteristics in a spatially and temporally autocorrelated system (Forman 1995, Morgan et al. 2001). In some cases fire mediates switches between alternative vegetation types resulting in positive fire-vegetation interactions (Vilà et al....

Woody plant encroachment in savannas may alter carbon (C) and nitrogen (N) pools over the longterm, which could have regional or global biogeochemical implications given the widespread encroachment observed in the vast savanna biome. Soil and litter %C and %N were surveyed across four soil types in two encroached, semiarid savanna landscapes in northern South Africa. Litter at sampling points with a woody component had a higher %N and lower C : N ratio than litter at solely herbaceous points. Severely encroached areas had lower C : N ratios throughout the soil profile than less encroached...

Tucker and Townshend (2000) conclude that wall-to-wall coverage is needed to avoid gross errors in estimations of deforestation rates' because tropical deforestation is concentrated along roads and rivers. They specifically question the reliability of the 10% sample of Landsat sensor scenes used in the global remote sensing survey conducted by the Food and Agricultural Organization (FAO) of the United Nations. They base their conclusion on simulations with data from Bolivia, Columbia and Peru, in which the size of a 10% sample is 4 less-than or equal to n less-than or equal to 6 Landsat...

Temperature sensitivity of community-level physiological profiles (CLPPs) was examined for two semiarid soils from the southwestern United States using five different C-substrate profile microtiter plates (Biolog GN2, GP2, ECO, SFN2, and SFP2) incubated at five different temperature regimes.The CLPPs produced from all plate types were relatively unaffected by these contrasting incubation temperature regimes.Our results demonstrate the ability to detect CLPP differences between similar soils with differing physiological parameters, and these differences are relatively insensitive to...

This paper examines the scientific merits of eight axioms of range or vegetative management pertaining to big sagebrush. These axioms are: (1) Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) does not naturally exceed 10 percent canopy cover and mountain big sagebrush (A. t. ssp. vaseyana) does not naturally exceed 20 percent canopy cover; (2) As big sagebrush canopy cover increases over 12 to15 percent, bare ground increases and perennial grass cover decreases; (3) Removing, controlling, or killing big sagebrush will results in a two or three or more fold increase in...

Management of coarse woody debris following fire requires consideration of its positive and negative values. The ecological benefits of coarse woody debris and fire hazard considerations are summarized. This paper presents recommendations for desired ranges of coarse woody debris. Example simulations illustrate changes in debris over time and with varying management.

Evidence for global warming over the past 200 years is overwhelming (Hulme et al. 1999), based on both direct weather observation and indirect physical and biological indicators such as retreating glaciers and snow/ice cover, increasing sea level, and longer growing seasons (IPCC 2001). Recent GCM projections of the Hadley Centre (Gordon et al. 2000) for Siberia show an increase in temperature of 4º C to 6º C and an increase in precipitation of as much as 25% by 2100. These changes, moreover, could occur at a rate of 0.1º C to 0.4º C per decade (Watson et al., 1996).The rapid rate of...