Gap-Scale Disturbance Patterns and Processes in a Montane Pinus palustris Woodland

Abstract

Gap-scale disturbances drive successional and structural development patterns in most forest ecosystems. Although fire-maintained Pinus palustris woodlands are less light limited than closed canopy forests, gap-scale disturbance processes may still influence successional and developmental pathways. We quantified biophysical characteristics of 50 canopy gaps in a montane Pinus palustris woodland to analyze gap-scale disturbance patterns and processes. We found most gaps (64%) were caused by the death of a single tree. Snag-formed gaps were most common (38%) followed by snapped stems (32%). We hypothesized that insect-induced mortality, perhaps in combination with drought periods, resulted in the high frequency of snag- and snapped stem-formed gaps. We did not find significant differences in gap size or shape based on gap formation or closure mechanisms. Most gaps (74%) were projected to close by lateral crown expansion of gap perimeter trees. We hypothesized most gaps projected to close via subcanopy recruitment would be captured by a P. palustris stem. The majority of gaps were small and gap frequency declined with increased gap size. We found gaps were significantly clustered through the woodland at distances of 8–36 m from gap edge to gap edge but were randomly distributed beyond 36 m.