Document: RAC-3-67-14

The role of fire, deer herbivory and canopy gaps on tree species composition in eastern deciduous forests: Implications for succession theory.

COLLINS, R.J.* and W.P.CARSON

University of Pittsburgh, Pittsburgh, PA 15260 USA ¹

Abstract:
Successional theories and models for second growth eastern deciduous forests predict that species composition should shift over time from pioneer, shade-intolerant species to late-successional shade-tolerant species. Succession models based solely on shade tolerance fail to predict changes occurring in many eastern forests. Why does successional theory not fit common patterns? Probably because other factors that are as important as shade tolerance come into play. To understand the mechanisms that control forest composition and succession, we are testing the roles of fire, deer herbivory and canopy gaps on the growth and survival of a 35 tree species at the Westvaco Research Forest in northeastern West Virginia. We have established 64, 400 m² subplots where we have permanently tagged, identified and measured nearly 17,000 seedlings, saplings and adults. We have experimentally manipulated fire, browsing by deer, and canopy gap formation in these plots in a factorial design. Here, we report the first year post treatment results. Sprouts on standing dead trees (a major regeneration mechanism the region) were three times taller inside fences compared to spouts in unfenced plots. Northern red oak (Quercus rubra) seedling height increased by 60% in fenced gaps and decreased by 20% in unfenced gaps (P< 0.05). Black cherry (Prunus serotina) showed the same pattern (P< 0.05). Fires promoted grape vine (Vitis spp. ) and pin cherry (Prunus pensylvanica) germination. The hottest fires topkilled 60-100% of the saplings. These results show that deer mask the effects of canopy gaps and fires can control understory species composition. Our overall goal is to elucidate the underlying mechanisms that, along with shade tolerance, control forest tree species composition and succession.

Keywords: canopy gaps, forest ecology, fire, deer herbivory, shade tolerance

This abstract is being presented at: 10:45 AM in session:
Oral Session #22: Multiple Disturbance Effects, Including Fire.