Changes in Plant Composition Following Disturbance in Restored Native Early Successional Communities

Abstract

Restoration of nonnative grasslands to native early successional plant communities has been a conservation focus throughout the United States for several decades. In the eastern US, where precipitation exceeds 1 000 mm per year, disturbance is necessary following restoration to prevent early successional communities from progressing into woody-dominated midsuccessional communities. Resulting plant composition may vary among disturbance practices, and knowledge of such effects will help direct maintenance of restored native early seral plant communities. We evaluated the effects of the two most common disturbance practices, prescribed fire and mowing, following restoration of nonnative grasslands to native plant communities via two methods: 1) planting native grasses and 2) forbs and seedbank response without planting, across 11 replicated sites in Tennessee and Alabama, 2018–2020. Specifically, we evaluated how disturbance altered vegetation composition following four treatment combinations (planted mowed, planted burned, seedbank mowed, and seedbank burned) and tall fescue (Schedonorus arundinaceus) control from predisturbance conditions. Grass coverage increased in all treatment units, but tended to increase more in mowed treatments than burned treatments. Forb coverage declined in all treatments except seedbank burned, where it increased. Similarly, spring-, summer-, and fall-flowering forbs, which are the focus of conservation programs designed to enhance habitat for pollinators, increased most in seedbank burned. Species richness decreased across all treatments and control, except seedbank burned, where it increased. The species evenness did not differ by treatment. Our results provide insight into how disturbance techniques may alter plant community composition soon after restoration. We recommend managers use prescribed fire instead of mowing if increased forb coverage is important to meet objectives. Furthermore, our results highlight how planting native grasses and forbs is not necessary to restore native early successional plant communities on most sites dominated by nonnative grasses in the eastern United States, where precipitation is not limiting succession.