Primary productivity and water use in native forest, grassland, and desert ecosystems

The relationship between aboveground net primary production (ANPP) and water usevaries significantly among ecosystem types. For both hot deserts and shortgrass prairie—cold desertswhich are water limited, ANPP is linearly related to annual water use above a minimum amount ofwater, estimated at 38 and 170 mm, respectively, needed annually to sustain each system. Once theminimum water to sustain ANPP is reached, ANPP increases an estimated 0.38 g and 1.09 g per 1000g of additional water in the hot desert and the shortgrass prairie—cold desert. In forest systems notwater stressed, ANPP was not related to water use. For grasslands representing a gradient from waterstressed toward not water stressed, ANPP correspondingly declined per unit of water used. Classicallyevaluating water-use efficiency as annual ANPP divided by annual evapotranspiration, forests are themost efficient, 0.9 to 1.8 g ANPP/1000 g water, followed by shortgrass prairie, 0.2 to 0.7, then hotdeserts, 0.1 to 0.3.
Key words: deserts; evapotranspiration; forests; grasslands; primary production; water-use ef-ficiency.