Snag dynamics and forest structure in Afromontane forests in KwaZulu-Natal, South Africa: implications for the conservation of cavity-nesting avifauna

Abstract

Little is known about snags in South African indigenous forests. Because of their value to wildlife, we initiated this study to quantify snag characteristics and dynamics. We also investigated forest structure (woody component and snags) and forest use by avian species of conservation concern. We examined tree species composition, abundance and tree size in eight Afromontane mixed Podocarpus forests in KwaZulu-Natal, South Africa. In addition, we investigated the succession of snags at the level of individual trees. Large Podocarpus species were less abundant in forests of the Dargle district than forests in the Creighton district. Mean diameter at breast height (dbh) of trees in the forests in these two districts differed significantly. Emergent and upper canopy trees (trees > 50% of estimated 100% canopy height) were smaller in the Dargle district than those in the Creighton district. Although frequency of smaller trees (dbh = 10–60cm) compared with larger trees was high in both districts, forests in the Creighton district had more large trees. Snags were rare in all forests, but were larger (dbh) in forests of the Creighton district. The availability of large snags in these forests has implications for the conservation of secondary cavity nesting bird species including the Endangered Cape Parrot, Poicephalus robustus, as they are necessary for reproduction and recruitment of these birds.