An assessment of production trends on the Great Plains from 1984 to 2017

Authors: REEVES, MATTHEW - Us Forest Service (FS); HANBERRY, BRICE - Us Forest Service (FS); Wilmer, Hailey; Kaplan, Nicole; LAUENROTH, WILLIAM - Yale University

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2020
Publication Date: N/A
Citation: N/A

Interpretive Summary: In the Great Plains, above ground annual net primary productivity (ANPP) is a critical ecosystem service supporting billions of dollars of the economy. Managers and producers struggle with high interannual variability in ANPP which often varies 40 percent between years due to fluctuating precipitation and drought. To measure this, we created the Rangeland Production Monitoring Service (RPMS), a spatially explicit database with automatic annual updates of ANPP for all rangelands in the coterminous US from 1984 to present. Our study looks at these relationships each year between 1984-present, and we also compared this to production data collected at sites across the region on the ground. We find significant (a = 0.05) increases in ANPP since 1984 across all major grassland types in the Great Plains, particularly the northern mixed grass prairie, which also has the greatest interannual variability (21%).

Technical Abstract: Throughout the Great Plains, above ground 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 variability in ANPP which often varies 40 percent between years due to fluctuating precipitation and drought. To quantify ANPP trends and evaluate interannual and spatial variability, we created the Rangeland Production Monitoring Service (RPMS), a spatially explicit database with automatic annual updates of ANPP for all rangelands in the coterminous US from 1984 to present. 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 r2 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 variability of ANPP in the Great Plains region for four major grassland types, smaller scale Ecological Subsections, and National Grassland units. Significant (a = 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 has the greatest interannual variability (21%). Corresponding significant increases (p < 0.1) in growing season precipitation were found in all grassland types except the shortgrass steppe. Spatial variability decreases from west to east and tallgrass prairie exhibits the lowest temporal and spatial variability of 8% and 21% respectively. Grazing allotments in the National Grasslands exhibit differential recovery after drought ranging from about 15% to 350%.