Zhang et al. have a paper in Early View titled “Forest productivity increases with evenness, species richness and trait variation: a global meta-analysis“. Read it here.
The authors have provided a succinct description of their paper in the Journal.
Although artificial experiments with grasslands suggest productivity increases with plant diversity, robust evidence for the world’s forests has been lacking. In our current paper we show that at the global scale, productivity in forest polycultures (mixtures of species) is on average ≈25% higher than when trees are grown one species at a time in monocultures. Thus, greater diversity regularly yields greater productivity, especially when tree species that can thrive in deep shade and bright sun are both part of the forest, Moreover, the effects of diversity grow larger as forests become older and more mature. These diversity effects were similar in both planted and natural stands across boreal, temperate, and tropical forests. Our analysis highlights the importance of species diversity and life-history trait heterogeneity in the functioning of global forest ecosystems. Our results imply that that conversion from forests of diverse species to monocultures will reduce forest productivity and impair the role of global forests in carbon storage and sequestration. Moreover, managing for forest diversity will be an effective means to reduce emissions from forest degradation. Further research should strive to understand how species diversity, life-history variation, and stand development influence hypothesized niche differentiation, facilitation, niche utilization, interactions with natural enemies, and other novel mechanisms that are responsible for positive diversity effects on ecosystem function.