Tropical forest structure: a missing dimension to Pleistocene landscapes

Abstract

AbstractBy focusing on the horizontal distribution of Pleistocene vegetation types within tropical landscapes, we may be overlooking an equally important feature of palaeovegetation, namely their vertical structure. Tropical forest structure is a critical factor contributing to canopy microclimatology and thus plays a role in defining canopy habitats and species population dynamics. Because of this tight relationship between forest structure and canopy microclimate, flora and fauna with narrow canopy niches may have responded to glacial reductions in forest canopy density in the same manner as if the tropical forest were completely replaced by grassland. This alternative interpretation of palaeo‐forest response to past climate change holds significance for the application of the Pleistocene refugia hypothesis in explaining various biogeographical trends. The role of forest structure in influencing hydrological cycling and the exchange of carbon between the biosphere and atmosphere are highlighted to illustrate how palaeoprecipitation and palaeoproductivity proxy data may be misinterpreted when forest structure is not explicitly considered. This is accomplished through theoretical scenarios using hydrological mass balance equations and simulations using a soil–plant–atmosphere landscape model. Available methodologies to reconstruct tropical palaeovegetation structure are identified, including the use of fully coupled earth system models. Copyright © 2004 John Wiley & Sons, Ltd.