Estimating biogeochemical fluxes across sagebrush-steppe landscapes with Thematic Mapper imagery

Abstract

Thematic Mapper (TM) satellite data were coupled to an ecosystem simulation model to simulate variation in nitrogen mineralization over time and space in a sagebrush steppe. This system of data inputs and calculations provides estimates of ecosystem properties including rates of biogeochemical processes over extensive and complex landscapes, and under changing management and climatic conditions. The landscape surface was divided into three sagebrush ecosystem types plus one other class consisting of nonsagebrush vegetation. It was possible to subdivide vegetation further with TM data but this relatively simple classification was necessitated by limited parameterization of the simulation model. Nevertheless, this classification presented a complex mosaic of ecosystem types that shifted markedly in composition from one end of the 933 km 2 study area to the other. Annual N-mineralization rates ranged from 5 to 25 kg N ha −1 among the three sagebrush types. The most active type comprised 42% of the entire area but contributed 60% to the nitrogen mineralization throughout the landscape.