Impact of plant diversity and management intensity on magnitude and stability of productivity in North American grazing lands

Authors: SONNIER, GREGORY - Archbold Biological Station; Augustine, David; PAUDEL, SHISHIR - Phipps Conservatory And Botanical Gardens; Porensky, Lauren; SILVEIRA, MARIA - University Of Florida; Toledo, David; AZAD, SHEFALI - Archbold Biological Station; BOUGHTON, RAOUL - Mosaic Co; Browning, Dawn; Clark, Pat; Fay, Philip; Kaplan, Nicole; THIBAULT, KAT - Neon, Inc; SWAIN, HILARY - Archbold Biological Station; Veum, Kristen; BOUGHTON, ELIZABETH - Archbold Biological Station

Submitted to: Applied Vegetation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2024
Publication Date: 5/16/2024
Citation: Sonnier, G., Augustine, D.J., Paudel, S., Porensky, L.M., Silveira, M., Toledo, D.N., Azad, S., Boughton, R., Browning, D.M., Clark, P., Fay, P.A., Kaplan, N.E., Thibault, K., Swain, H.M., Veum, K.S., Boughton, E. 2024. Impact of plant diversity and management intensity on magnitude and stability of productivity in North American grazing lands. Applied Vegetation Science. 27(2). Article e12776. https://doi.org/10.1111/avsc.12776.
DOI: https://doi.org/10.1111/avsc.12776

Interpretive Summary: Grasslands are one of the most important sources of forage for livestoc worldwide and their management affects the level of forage production. Management intensification is a widespread land use change and has accelerated across the U.S. to meet rising demands on productivity, but we still have limited understanding of how relationships between plant diversity and plant productivity are affected by management. We studied the relationship between plant diversity and grassland productivity across 9 regions of the continental United States. We then evaluated how management intensification was related to plant diversity and productivity in at 4 of these locations. We used satellite measurements to estimate plant productivity, and used ground measurements conducted by two ecological networks (NSF’s National Ecological Observatory Network and USDA’s Long-Term Agroecosystem Research Network) to quantify plant diversity. We found the plant production over time was most stable within each region when plant diversity was hight. However, for the 4 locations where examined management intensification, we found mixed results. In one case study, species-poor, intensively managed pastures presented the highest productivity but were more sensitive to dry conditions than less intensified pastures. However, in other case studies, we did not observe significant effects of management intensity on the amouont or stability of productivity. Generalization across studies may therefore be difficult and require developing intensification indices general enough to be applied across diverse management strategies in grazinglands.

Technical Abstract: Grasslands provide important provisioning services worldwide and their management has consequences for these services. Management intensification is a widespread land use change and has accelerated across the U.S. to meet rising demands on productivity, yet its impact on the relationship between diversity and productivity is still unclear is. Here, we investigated the relationship between plant diversity and grassland productivity across 9 eco-climatic domains of the continental United States. We then tested the effect of management intensification on diversity and productivity in 4 case studies. We acquired remotely sensed GPP data from Google Earth Engine (1986 to 2018, 30 m resolution, 16-day cadence) and plant diversity data measured at different spatial scales (1, 10, 100, 400-m2) from two ecological networks (NSF’s National Ecological Observatory Network and USDA’s Long-Term Agroecosystem Research Network). Across all sites, we observed positive relationships among species richness, productivity, and the temporal stability of mean annual biomass production (1986-2018). These relationships were not affected by the scale at which species richness was observed. However, across all 4 case studies, we observed that management effects on species richness were only significant at broader scales (i.e., =10-m2) with no clear effect found at the commonly used 1-m2 quadrat scale. In one case study, species-poor, intensively managed pastures presented the highest productivity but were more sensitive to dry conditions than less intensified pastures. However, in other case studies, we did not observe significant effects of management intensity on magnitude or stability of productivity. Generalization across studies may therefore be difficult and require developing intensification indices general enough to be applied across diverse management strategies in grazinglands. Understanding how management intensification affects the magnitude and stability of provisioning services will inform the development of sustainable intensification strategies.