Effects of Repeated Clipping and Litter Removal on Survival of Fire-Dependent Herbs of Wet Pine Savannas

Temperate savannas and grasslands maintained by frequent, low-intensity fires are among the most species-rich plant communities in the world. One untested mechanism by which frequent fires increase plant species diversity is increased survival of fire-dependent species. I examined how the frequency of simulated fire (clipping combined with litter removal) affected the survival of nine fire-dependent, perennial groundcover plant species over two growing seasons at each of two pine savannas in southeastern Mississippi (USA). I established two experiments. Experiment 1 examined transplant survival from May 2017 to October 2018 of five moderately common species in plots treated annually from 2014 to 2017 and in adjacent untreated plots. The five species were Bigelowia nudata, Rhynchospora latifolia, Carphephorus pseudoliatris, Eriocaulon compressum, and Triantha racemosa. Experiment 2 examined the effect of reducing treatment frequency in 2018 in Experiment 1 plots on survival from May 2022 to October 2023 of naturally occurring individuals of the four most fire-responsive species (Drosera capillaris, Dichanthelium ensifolium, Pseudolycopodiella caroliniana, and Rhynchospora oligantha). Survival of transplants varied significantly among species but was not greater in frequently treated plots than in untreated plots. Reducing treatment frequency did not cause a significant decline in post-treatment survival of any of the four species monitored in situ. Results do not support the hypothesis that frequent fires increase 2 y survival of established individuals of fire-dependent species. Results are consistent with a hypothesis that frequent reductions of standing dead and litter by fire maintain species diversity by instead improving conditions for recruitment of fire-responsive species.