The Causes and Sizes of Canopy Gaps in the Southern Cape Forests

Abstract

The Southern Cape indigenous forests are not subject to regular major disturbances. The most frequent cause of canopy gaps is single trees dying standing, with an average gap size of 150 m². Windfall gaps are caused by the uprooting of smaller trees (210 m²) and by the snapping at the base of larger, partly rotten live trees (330 m²). Gaps caused by felled trees (450 m²) are significantly larger than natural gaps. The results indicate that a single tree selection system will most closely resemble the natural disturbance processes. The large gaps, especially after logging disturbance, cause deterioration of the microclimatic and soil conditions. Recommendations are provided to ensure that during logging operations canopy gap sizes are minimized and suitable site conditions are maintained in the gaps to ensure good regeneration of tree species.