Abstract. Ecosystem management is management driven by explicit goals, executed by policies, protocols, and practices, and made adaptable by monitoring and research based on our best understanding of the ecological interactions and processes necessary to sustain ecosystem composition, structure, and function.In recent years, sustainability has become an explicitly stated, even legislatively mandated, goal of natural resource management agencies. In practice, however, management approaches have often focused on maximizing short-term yield and economic gain rather than long-term sustainability. Several obstacles contribute to this disparity, including: ( 1) inadequate information on the biological diversity of environments; (2) widespread ignorance of the function and dynamics of ecosystems; (3) the openness and interconnectedness of ecosystems on scales that transcend management boundaries; (4) a prevailing public perception that the immediate economic and social value of supposedly renewable resources outweighs the risk of future ecosystem damage or the benefits of alternative management approaches. The goal of ecosystem management is to overcome these obstacles.Ecosystem management includes the following elements: (1) Sustainability. Ecosystem management does not focus primarily on "deliverables" but rather regards intergenerational sustainability as a precondition. (2) Vol. 6, No.3 goals that specify future processes and outcomes necessary for sustainability. (3) Sound ecological models and understanding. Ecosystem management relies on research performed at all levels of ecological organization. (4) Complexity and connectedness. Ecosystem management recognizes that biological diversity and structural complexity strengthen ecosystems against disturbance and supply the genetic resources necessary to adapt to long-term change.(5) The dynamic character of ecosystems. Recognizing that change and evolution are inherent in ecosystem sustainability, ecosystem management avoids attempts to "freeze" ecosystems in a particular state or configuration. (6) Context and scale. Ecosystem processes operate over a wide range of spatial and temporal scales, and their behavior at any given location is greatly affected by surrounding systems. Thus, there is no single appropriate scale or time frame for management. (7) Humans as ecosystem components. Ecosystem management values the active role of humans in achieving sustainable management goals. (8) Adaptability and accountability. Ecosystem management acknowledges that current knowledge and paradigms of ecosystem function are provisional, incomplete, and subject to change. Management approaches must be viewed as hypotheses to be tested by research and monitoring programs.The following are fundamental scientific precepts for ecosystem management.(1) Spatial and temporal scale are critical. Ecosystem function includes inputs, outputs, cycling of materials and energy, and the interactions of organisms. Boundaries defined for the study or management of one process are often inapp...

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Measurements of carbon, nitrogen, and phosphorus content were carried out in the soils of a hillslope of shortgrass steppe. Plant biomass, soil morphology, and soil physical properties were also measured. Soil morphology indicated that the site had undergone several cycles of rapid erosion and deposition. Total mass of C, N, and P increased downslope, following a trend in soil depth, but the summit A horizon had higher C, N, and organic P concentrations than the backslope, reflecting a higher clay content. Laboratory and field incubations showed that N availability increased downslope, while relative N mineralization (N mineralized: total N) decreased. Organic matter content and mineralization rate were closely coupled to physical properties of the soil, which reflect the geomorphic history of the site.

Factors hzfluencing distribution of free-roaming cattle were studied on shortgrass steppe in northeastern Colorado. Spatial units selected for grazing were plant communities (soil-plant associations) and a stock-watering area. Regression models of grazing patterns were derived for growing-and dormant-season grazing patterns. Seasonal-grazing distribution was correlated with proximity to water (l/distance) and site-quality indicators. Internal validation of seasonal-grazing models indicated a good flt of predicted to observed patterns. Because ad hoe regression models lack wide applicability, relationships between spatial preference and vegetation properties were investigated. Combined relative measures of forage quality and quantity were good predictors of community preference. Measures of relative biomass or frequencies of forage species were poor predictors of spatlal preference. The high correlation between preference and properties of plants composing the bulk of the diet suggests an interaction between diet selection and selection of grazing areas. The highest correlation occurred between relative community preference and relative aboveground standing nitrogen (crude protein). Animal distribution is considered an important component of livestock management. We have only generalities, no quantitative, predictive knowledge about what factors influence grazing-animal distribution, how those factors change over time, or how distribution is related to nutrition. Systematic investigation of mechanisms behind distribution of range livestock is lacking. Because distribution is traditionally described in terms of use of predetermined zones, areas actually selected by animals for grazing are often not known. Predicting livestock distribution requires precise quantification of behavior and contributing environmental variables. This paper describes a study of spatial patterns of cattle grazing on shortgrass steppe. The objectives of this research were to determine (1) which spatial components of the landscape are selected as grazing habitat by cattle, (2) what factors influence spatial patterns of seasonal or

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