Long-term environmental change in tropical forests: increasing tree turnover

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Abstract
Summary: Analyzing permanent plot data from 40 tropical forest sites, Phillips and Gentry (1994) found that there has been a significant tendency for tree turnover – as measured by tree mortality and recruitment – to increase since the 1950s. The dataset is now substantially improved, and includes 67 mature forest sites with turnover data representing most of the major tropical forest regions of the world. This paper presents an updated and expanded analysis of the latest data, and confirms that tree turnover has increased in mature tropical forest plots. Several artifactual explanations have been suggested but none are supported by the available data, suggesting that surviving mature tropical forests have been recently affected by large-scale anthropogenic or natural change. The effects of increased turnover may include impacts on future global atmosphere, climate, and biodiversity. Better understanding of the ecological changes in mature tropical forests depends on progress in two critical research areas – a ground-based monitoring network of long-term, fully identified tropical forest plots, and controlled manipulation of atmospheric conditions in forest experiments. Research activity in both areas needs to be substantially increased if we are to understand and predict the complex interactions between tropical forest ecology and global environmental change.