The resistance and resilience of Great Plains ecoregion boundaries to the 1930s drought as a lens to future dynamics

Authors: BURRUSS, N. DYLAN - New Mexico State University; PETERS, DEBRA - Retired ARS Employee; Huang, Haitao

Submitted to: Ecosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2023
Publication Date: 5/21/2023
Citation: Burruss, N., Peters, D.C., Huang, H. 2023. The resistance and resilience of Great Plains ecoregion boundaries to the 1930s drought as a lens to future dynamics. Ecosphere. 14(5). Article e4538. https://doi.org/10.1002/ecs2.4538.
DOI: https://doi.org/10.1002/ecs2.4538

Interpretive Summary: Severe drought events have variable effects on grasslands at a regional to continental scale, but the causes of these variations are poorly understood. The authors used a big data-model integration approach to analyze variations in grassland production before, during, and after the “Dust Bowl” drought of the 1930s in the Central Great Plains Region of Iowa and Nebraska. Climate and soil factors predicted grass production prior to the drought, yet additional land use and erosion factors were needed to explain production in both drought and post-drought. Tallgrass prairie exhibited stronger production responses to precipitation and temperature compared with northern and southern mixed-grass prairies during all periods. Tallgrass prairie counties along the boundary with mixed-grass prairies were more negatively impacted by soil loss from abandoned cropland during the drought compared with other tallgrass prairie counties. The modeling approach provides a method to predict broad-scale variations in resilience to extreme drought in response to climate, soils, and land management.

Technical Abstract: Potential natural vegetation (PNV) remains an important concept in ecology by providing the basis for comparing current or future conditions and trends in vegetation with historic conditions. However, nonstationary climate and land-use-driven deviations from baseline conditions challenge the validity of PNV at local scales or for locations that are especially sensitive to environmen-tal changes, such as ecotonal boundaries between ecosystem types. Our goal was to identify the historic boundaries between major grassland types in the Central Great Plains (CGP) of North America (tallgrass prairie and northern and southern mixed-grass prairies) by examining the environmental drivers of primary production prior to, during, and after the decades-long drought in the 1930s. We sought to explore differences among grassland types in resistance and resilience to drought, and to evaluate legacy effects resulting from spa-tially explicit processes during drought. We used county-level cropland pro-duction data from 1926 to 1948 as a proxy for native grass production data. We regressed production data against a suite of models containing variables associ-ated with climate, soils, land use, and drought indices prior to, during, and after drought. We used a dimension reduction approach to identify the loca-tions of grassland boundaries in multivariate space defined by each model. Our results show that climate and soil factors predicted grass production prior to the drought, yet additional land use and erosion factors were needed to explain production in both drought and post-drought. Grassland responses were most variable along ecotonal boundaries. Tallgrass prairie exhibited stronger production responses to precipitation and temperature compared with northern and southern mixed-grass prairies during all periods. Tallgrass prai-rie counties along the ecotone with mixed-grass prairies were more negatively impacted by soil loss from abandoned cropland during the drought compared with other tallgrass prairie counties. As the intensity and frequency of drought are predicted to increase, landscape-scale variables and spatially explicit processes that govern novel production responses will need to be accounted for in explaining heterogeneity in grassland responses.