Where have you bean? Understanding the distribution and abundance of legumes in grasslands across a precipitation gradient in Kansas

Abstract

Legumes are important in grasslands and other nutrient-limited, terrestrial ecosystems by fixing atmospheric nitrogen, facilitating nutrient cycling, and increasing species diversity above and below ground. Despite many studies that show the potential impacts legumes have on ecosystems, the distribution and abundance of native legumes species in North American grasslands is not well understood. North American grasslands, especially remnant untilled prairie, is a dwindling habitat because much of its historical range has been converted to industrialized agricultural. In order to understand the distribution and abundance of native legume species and to better conserve them, we collected vegetation and soil data across a longitudinal precipitation gradient (450-1100 mm annually) in Kansas from 108 restored grasslands, part of the Conservation Reserve Program (CRP) sites, and 22 untilled references sites during the summers of 2019 and 2020. Mean annual precipitation and land use history were the most important predictor of overall species richness and legume species richness. There was a significant disparity between legume species richness on restored and untilled prairies at the wettest end of the precipitation gradient which suggests that the results of the conservation practice used on eastern restored sites are not representative of untilled eastern prairies. Non-native legumes occurred more often on restored sites than untilled sites. Additionally, because native legume species occurred less often on restored sites, disturbance and management practices may limit native legume species establishment and benefit non-native species establishment. These results provide important information on native legume species abundance and provide a stepping-stone to better understanding grassland ecology as a whole.