Effects of temperature and soil texture on ANPP in the US great plains

Aboveground net primary production (ANPP) in grassland ecosystems is positively related to mean annual precipitation (MAP). However, at any given level of precipitation, other factors may effect ANPP. Our objective was to determine the importance of temperature and soil texture in explaining ANPP in the Great Plains of the United States. We constructed a spatial database of ANPP, climate, and soil texture for the region using a geographic information system. Holding MAP constant at 5-cm intervals, we related ANPP to mean annual temperature (MAT), and soil sand and clay contents. Our findings indicate that MAT and soil texture are important variables for explaining patterns of ANPP, after accounting for the variability explained by MAP. There is a negative relationship between temperature and ANPP when MAP is held constant; this has important climate-change implications. Results revealed an MAP crossover point for the inverse texture effect at similar to 80 cm of rainfall, much higher than previously reported. The consequences of this are substantial for grasslands throughout the globe, where precipitation ranges between 25 and 100 cm.