Multiple Disturbances, Multiple Legacies: Fire, Canopy Gaps, and Deer Jointly Change the Forest Seed Bank

Abstract

The manipulation of pre-colonial disturbances in U.S. forests can play a critical role in determining ecological composition, structure, and function. However, our understanding of how concurrent disturbances influence non-tree species is extremely limited in forests. To this end, we used a long-term, multi-disturbance experiment in an oak dominated forest in West Virginia, U.S.A. that factorially manipulated understory fire, deer fencing, and canopy gaps. Thirteen years after disturbance initiation, we sampled and germinated the seed bank from each disturbance treatment. We found long-term seed banks differed only in plots with understory fire, with effects contingent on canopy gaps and deer fencing. Fire combined with canopy gaps caused a 205% increase in seed abundance. Combined fire, deer fencing, and canopy gaps led to the lowest diversity of all treatments and the dominance of the shrub Rubus in the seed bank, reflecting the continued legacy of extant plants that grew immediately after disturbance. Lastly, in plots with multiple reintroduced disturbances, seed communities were distinct from extant understory species at all time points, highlighting how the seed bank is an important reservoir of biodiversity. Each reintroduced disturbance combination left a unique legacy in the seed bank that will likely influence future forest reorganization following disturbance, adding to our understanding of how disturbances influence forest succession and organization. Our study highlights the many unexpected ways that multiple disturbances can change an understudied, but influential, component of the forest for well over a decade.