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Maximising biodiversity and forest productivity simultaneously is possible in moist climates shows new study by Professor David Wardle
Forest ecosystems worldwide vary hugely in both diversity and productivity, and whether to maximize productivity or conserve biodiversity is an important trade-off for forest management. But is maximizing diversity and productivity necessarily contradictory? Over the past 40 years, ecologists have explored the relationship between biodiversity and productivity in many natural ecosystems. Different studies have found contrasting patterns; productivity have been found to both increase and decrease with diversity, or even be greatest at intermediate diversity. We know very little about why this variation of patterns occurs, or how environmental context determines the form and even the direction of the productivity-diversity relationship. The fact that most studies on this topic focus on simple and/or experimentally assembled conditions and only look at a narrow range of environmental conditions further limits our understanding of how real ecosystems work.
In a paper just published in Nature Communications, a team of researchers including Professor David Wardle at the ASE and colleagues from Purdue University, Peking University, the US Forest Service and SCION, explore this question for 115,000 forest plots spanning the full range of climatic conditions found within the contiguous United States. They used a Bayesian analytical framework to pin down the most important regional factors determining the relationship between productivity and biodiversity for these forest ecosystems. Precipitation turned out to be a strong determinant of the nature of the biodiversity-productivity relationship. In dry climates the relationship tended to have be positive or neutral, while in humid climates the relationship was hump-shaped. These relationships were further mediated by variation in forest stand age and density, and by soil properties.
This study has important implications for management of forests, especially where the management goal is to simultaneously maximize tree species diversity and productivity. It highlights that at least in the US, maximum tree diversity and productivity can be achieved simultaneously for regions where the climate is moist, but that trade-offs need to be made in maximizing biodiversity versus productivity when the climate is more arid.