Primary production of the central grassland region of the United States

Confirms the overwhelming importance of water availability as a control on production. Lowest values of aboveground net primary production were observed in the west, highest values in the east. This spatial pattern was shifted eastward during unfavorable years, westward during favorable years. Variability in production among years was maximum in N New Mexico and SW Kansas and decreased towards the N and S. The regional pattern of production was largely accounted for by annual precipitation. Production at site level was explained by annual precipitation, soil water-holding capacity, and an interaction term. When precipitation is <370 mm/yr, sandy soils with low water-holding capacity are more productive than loamy soils with high water-holding capacity; the opposite pattern occurs when precipitation is >370 mm/yr. -from Authors