Rachel Standish

Forests need to be resilient and adaptive in the face of global environmental change and mixed species forestry is a critical strategy for achieving this goal. It has been shown in many studies that mixed species forests can be more productive, more resilient to stress and disturbance while also providing a broader range of ecosystem services relative to mono-specific forests, yet the underlying mechanisms are not clear. Contrasting inter-specific functional trait expression and increased structural heterogeneity in mixtures may enhance community resource utilization, which could help explain synergistic effects on tree growth. Here, we conducted a meta-analysis of data from 21 tree diversity experiments across 5 continents to determine the extent to which mixed forestry can promote increased growth as measured by stand-level basal area and height mean annual increment. We then used structural-equation modeling to quantify the strength of linkages between species diversity and growth via vertical and horizontal structural heterogeneity, functional trait diversity, and functional stand composition. We will discuss our findings in terms of general growth trends identified, and potential mechanistic diversity-productivity pathways in tree species mixtures. The results can contribute to informing policy-makers and forest managers about the overall effectiveness of mixed forestry.