Removing Duff Layers in Fire-suppressed Wetlands can Aid Habitat Restoration Efforts

Amphibians breeding in ephemeral wetlands within pine-dominated ( Pinus spp.) natural communities are less likely to persist in wetlands that have developed high canopy cover and low herbaceous groundcover in the absence of regular plant growing-season wildfires. The reintroduction of historic fire regimes, in conjunction with mechanical or herbicide removal of woody shrubs, can reduce the woody midstory in wetlands. However, certain conditions can hinder the reemergence of herbaceous groundcover in degraded wetlands even after the removal of the woody midstory. After four years of no discernible recovery of herbaceous vegetation at two Reticulated Flatwoods Salamander ( Ambystoma bishopi ) breeding wetlands, we conducted a duff-removal experiment to test whether duff accumulation was preventing herbaceous plant germination and growth. Using a paired design, we found that duff removal increased the number of sprouting stems by 30-fold compared to control plots (paired t-test: t 19 = 5.30; p < 0.001) and shifted vegetation communities towards more desirable herbaceous groundcover (PERMANOVA: F 1,34 = 19.14; p < 0.001). Fire is recognized as an important source of disturbance in longleaf ( Pinus palustris ) and slash ( P. elliottii ) pine forests of the southeastern United States, but the return of fire to degraded habitats may not be sufficient to fully restore historic conditions that are conducive to flatwoods salamander reproduction. Our results demonstrate that duff removal may be a critical component of wetland restoration to improve or accelerate the response of understory vegetation following canopy removal.