Maintenance and Dynamics of Rainforest Edges

Abstract

Deforestation and fragmentation of rainforest has become one of the major threats to global biodiversity and the massive loss of rainforest during the past decades has pushed the global biota to the edge of the global species extinction crisis. Despite the increasing public awareness and tremendous efforts made internationally to save the remaining rainforest, the deforestation rate continues to accelerate in many rainforest areas. This trend is due mainly to increasing human population and local or regional economical or political crises creating increased needs and demands on land use and rainforest products. In addition to the loss of large areas of wildlife habitat, a direct consequence of rainforest fragmentation is the increase in the extent of edges, through which “hostile” edge effects can have a profound impact on the dynamics of remaining rainforests. There is an urgent need to understand the underlying mechanisms that drive the dynamics of the rainforest edges and more important, the subsequent long-term impact on the local and regional rainforest. The main objective of the study described in this thesis has been to compare the patterns with which rainforest plants respond to the edge environment at different types of edges involving rainforests. The study was conducted within a fragmented subtropical rainforest complex in Lamington National Park, Southeast Queensland. Rainforest trees, lianas, seedling banks and soil seed banks were investigated at eucalypt forest/ rainforest, pasture/ rainforest and roadside rainforest edges. For each edge type, nine 100 m transects were established from the edge to rainforest interior and transects were extended 50 m into eucalypt forest and pasture for additional sampling of surrounding matrices. Vegetation surveys were conducted along the edge transects for the study of trees, lianas and seedlings. Soil seed banks were investigated by germination experiments conducted in a shade house, using soil samples collected along the edge transect. The results from the edge studies were compared with corresponding studies in a 1 ha rainforest reference plot located in a relatively undisturbed area within the rainforest interior...