Trial by fire : Postfire development of a tropical dipterocarp forest

Abstract

Over the past decades, uncontrolled forest fires have formed an increasing threat for tropical forests, often causing large-scale ecological and economic damage. My research shows that, even though the damage caused by the fire is enormous, a single fire does not cause the complete destruction of a tropical rain forest: A part of the trees survives the disturbance through above ground survival, or through resprouting from below ground parts. As a result of this local persistence, recolonisation by shade tolerant species is not necessary, and a relatively fast recovery of the forest is feasible. Notwithstanding this moderately positive conclusion, the long-term maintenance of forest cover is extremely insecure after a fire has occurred. The mechanisms of persistence are not sufficient to ensure local survival of shade tolerant species in the wake of repeated disturbances, with rapid degradation of the vegetation as the result. The recovery potential as observed in our research is seriously constrained if additional disturbances are caused by commercial logging of dead trees after fire, or if repeated fires occur. Such disturbances must be avoided if the long-term objectives are to maintain a forest and to secure the productivity of a timber concession. The high persistence capacity of shade tolerant tree species after a single fire was unexpected. Until now, this aspect played a minor role in theoretical models that describe succession after severe disturbance. The results of my study suggest that certain elements of succession theory have to be adjusted, in order to increase the universal applicability of the theory. From a conservation perspective, the burned forests of East Kalimantan form a meagre substitute for unburned forest. Nevertheless, the high remaining species diversity, surviving populations of timber species and evident recovery potential make these forests worthwhile to be actively protected.