Long‐term late season mowing maintains diversity in southernUStallgrass prairie invaded byBothriochloa ischaemum

Abstract

AbstractQuestionsWhile mowing is a viable management tool for the maintenance of diversity in grasslands, the suitability of mowing in grasslands with invasion by exotic plants is poorly understood. In this 18‐yr study, we investigate the effects of long‐term mowing on a tallgrass prairie community invaded by exotic yellow bluestem (Bothriochloa ischaemum;BOIS). We explore the influence ofBOISon species richness and composition in the face of different mowing treatments as well as monitoring any post‐treatment legacy effects.LocationNortheast central Oklahoma,US.MethodsA total of 144 permanent plots were laid out comprising eight treatments (i.e. all combinations of Mar, Jun and Sept, mows resulting in three single mows, three double mows, one triple mow and an un‐mowed control). Plots were mowed 1996–2011 and recovery was monitored through 2014. Repeated mixed modelANOVA,PERMANOVAand principal response curves were employed to analyse species richness and compositional changes from mowing. Correlation was used to explore the effects ofBOISon species richness.ResultsMowing resulted in higher species richness relative to the absence of mowing, with the highest levels being sustained in the late season mown plots throughout the study. Once mowing had ceased, early season mown plots declined in species richness down to the same levels as the un‐mown plots, concomitant with the sharpest increased cover ofBOISin these plots relative to all other treatments. Overall, we found a strong negative correlation betweenBOIScover and species richness. Species dissimilarity was highest between any plot that was mowed and the un‐mown controls, as well as between March and September only treatments.ConclusionsOur study highlights the potential of mowing in maintaining high species richness. However, the positive response to early season mowing of the exotic yellow bluestem and ensuing negative effect on species richness suggests thatBOIScan confound the favourable effects of mowing. We found only minor post‐treatment legacy effects, sinceBOISstrongly re‐established in the absence of mowing in all previously mown plots, especially the early season mown plots. Thus, we recommend sustained late season mowing to help control the spread ofBOISand maintain species‐rich grasslands.