Assessing impacts of drought on weed communities in the Great Lakes region

Abstract Drought can alter weed occurrence, interference with crops, and act as ecological filters altering community structure. Precipitation patterns in the Great Lakes region of the United States are predicted to vary due to climate change, and understanding the impact of drought on weed communities can support effective management practices. A two site‐year study was performed in East Lansing, MI, with combinations of two maize hybrids (drought tolerant and sensitive) and two levels of precipitation (ambient or reduced) to assess the effect of drought on weed community structure. Weed density, Simpson's Diversity Index, species evenness, indicator species, and community composition were assessed. Weed community structure was altered by precipitation but not by maize hybrid. Reduced precipitation had no impact in the June sampling but decreased weed density by 44% in July. Weed community structure was not altered in June; however, in July, weed communities under drought were more diverse and even than those under ambient precipitation. A variety of species and combinations were indicative of site‐year and the majority differed from each treatment and period of analysis. Annual grasses and Portulaca oleracea displayed greater density under ambient precipitation, and annual grasses and Chenopodium album under reduced precipitation. Overall, results demonstrate that reduced precipitation resulted in weed communities more diverse and even under drought, and that different species and combinations of species were indicative of ambient or reduced precipitation in both site‐years. Ultimately, integrated weed management will need to adapt to these changes for continued sustainable success.