Long-term stability of temperate Australian wet forest-moorland mosaics despite recurrent fires associated with late Holocene climate change

Abstract

Context The primary factors(s) responsible for the maintenance of Alternative biome states (ABS) in world forest biomes remains unclear and debatable, partly due to insufficient long-term ecological data from suitable ecosystem sites. The occurrence of moorland in southern and western Tasmanian wet temperate forest presents a suitable setting to test for ABS and understand the main stabilizing factors of ABS. Objectives We use a palaeoecological approach to test for ABS and identify the degree of vegetation change and the effect of climate change and fire occurrence associated with ABS in southern Tasmania. Methods Sediment sequence from sink-hole lake in a forest and nearby pond in southern Tasmania were analysed for pollen and charcoal to reconstruct histories of forest, moorland and fire in the Tasmanian Wilderness World Heritage Area (TWWHA). Reconstructions were compared to palaeoclimate record. Results Moorland and forest in southern Tasmania have occupied the same habitat for at least the last 2600 years, and neither past climate change nor fire occurrence affected the stability of the vegetation mosaic. We suspect that localized environmental settings, such as topography and edaphic conditions are the primary stabilizing factors of the forest-moorland mosaics. Conclusions The observed stable vegetation mosaics in our study is contrary to the dominant ecological paradigm of landscape dynamics currently used to manage the TWWHA, and there is a need to refine the ecological basis of fire management in the area. Similar targeted palaeoecological studies are needed to fully understand the underlying factors responsible for the persistence of treeless vegetation in world forest biomes.