Soil seed bank characteristics in rangelands with increasing invasion of Heteropogoncontortus or EragrostisLehmanniana

Abstract

Identifying impacts of invasive grasses on seed banks is critical in developing restoration strategies. Tanglehead (Heteropogon contortus) and Lehmann lovegrass (Eragrostis Lehmanniana) have increased throughout the Texas Coastal Sand Plain. We examined effects of tanglehead or lovegrass abundance (as reflected in cover) on seed banks in sites dominated by (1) invasives (tanglehead or lovegrass), (2) natives-without-invasives, or (3) natives-with-invasives (either tanglehead or lovegrass) in 3 consecutive years. The seedling emergence method was used to characterize seed banks. More tanglehead seedlings emerged in tanglehead-dominated sites than native-without-tanglehead sites in 2013 and 2014; seed bank size of native grasses (other than tanglehead) was unaffected by tanglehead; and there were fewer forbs in native-tanglehead mixtures than native-without-tanglehead or tanglehead-dominated sites. More lovegrass seedlings and fewer forbs emerged in lovegrass-affected sites. Tanglehead did not affect seed bank richness or diversity; richness and diversity were higher in native-lovegrass mixtures than in native-without lovegrass communities. Tanglehead and lovegrass affected species composition in 1 of 3 years and 2 of 3 years, respectively. Taken together, our results suggest that restoration of invasive-affected sites may be feasible without seed input.