PARENT SESSION
Contributed Oral Session 40: Forest Understories
Tuesday, August 9, 8:00 AM - 11:30 AM, Meeting Room 514 A, Level 5, Palais des congrès de Montréal

Small understorey gaps created by subsistence harvesters do not adversely affect the maintenance of tree diversity in a sub-tropical forest.

Boudreau, Stéphane^*,1, Lawes, Michael¹, ¹ Forest Biodiversity Research Unit, Pietermaritzburg, South Africa

ABSTRACT- Understorey gaps are common in subtropical forests where pole-size trees are harvested for building materials. The creation of artificial understorey gaps has the potential to affect tree regeneration and the maintenance of forest tree diversity by locally increasing resource availability (light, nutrients, moisture). Understorey tree gaps had significantly lower foliage density in the 3-10 m stratum and higher soil moisture, but fine root biomass and nutrient availability (N, P, K, Corg) were not different to controls in the intact understorey. Light intensity at the forest floor was a function of the age of the gap, greater in recent gaps but not different in older gaps from the controls in intact understorey. The early regeneration community in understorey gaps was different in composition from under intact understorey. Understorey gaps appeared to promote the regeneration of understorey species (density and species richness) by increasing community-wide seedling establishment of understorey species. However, understorey gaps had no effect on the early regeneration of canopy species. We argue that under low harvesting intensity (11.6 % of the available stems), understorey gaps have a neutral role in the long-term maintenance of understorey species diversity and no apparent role in the long-term maintenance of canopy tree species diversity. These results suggest that low levels of subsistence harvesting of understorey species has a limited effect on overall species composition of scarp forest.

Key words: Understorey gaps, Tree regeneration, Light intensity, Nutrients availability