Publication

Throughout the Great Plains, aboveground annual net primary productivity (ANPP) is a critical ecosystem service supporting billions of dollars of commerce and countless stakeholders. Managers and producers struggle with high interannual change in ANPP, which often varies 40% between years due to fluctuating precipitation and drought. To quantify ANPP trends and evaluate interannual and spatial variation, we created the Rangeland Production Monitoring Service (RPMS), a spatially explicit database with automatic annual updates of ANPP for all rangelands in the conterminous United States. The RPMS establishes relationships between normalized difference vegetation index (NDVI) from remote sensing data and ANPP from soil ecological site descriptions. These relationships were applied to NDVI data in each year from 1984 to present, although the present assessment focuses on the period from 1984 to 2017. Validation metrics include an r(2) of 89% between predicted and observed ANPP at three locations in the Great Plains. For this special issue, we assess data from the RPMS to quantify trends and variation of ANPP in the Great Plains region for four major grassland types, smaller-scale ecological subsections, and national grassland units. Significant (alpha < 0.05) increases in ANPP since 1984 were observed across all major grassland types in the Great Plains, particularly the northern mixed-grass prairie, which also had the greatest interannual variation (21%) from 1984 to 2017. Corresponding significant increases (P < 0.1) in growing season precipitation were found in all grassland types except the shortgrass steppe. Spatial variation decreases from west to east and tallgrass prairie exhibited the lowest temporal and spatial variation of 8% and 21%, respectively, from 1984 to 2017. Grazing allotments in the National Grasslands exhibit differential recovery after drought ranging from about 15% to 350%. (C) 2020 The Authors. Published by Elsevier Inc. on behalf of The Society for Range Management.