Abstract
The effect of biodiversity on primary productivity has been a hot topic in ecology for over 20 years. Biodiversity–productivity relationships in natural ecosystems are highly variable, although positive relationships are most common. Understanding the conditions under which different relationships emerge is still a major challenge. Here, by analyzing HerbDivNet data, a global survey of natural grasslands, we show that biodiversity stabilizes rather than increases plant productivity in natural grasslands at the global scale. Our results suggest that the effect of species richness on productivity shifts from strongly positive in low-productivity communities to strongly negative in high-productivity communities. Thus, plant richness maintains community productivity at intermediate levels. As a result, it stabilizes plant productivity against environmental heterogeneity across space. Unifying biodiversity–productivity and biodiversity–spatial stability relationships at the global scale provides a new perspective on the functioning of natural ecosystems.
Highlights
The effect of biodiversity on primary productivity has been a hot topic in ecology for over 20 years
Stress level might be the most important factor in modulating biodiversity effects on productivity, because: (1) stress is a broad concept that includes light, water, and nutrient availability, suboptimal temperatures, and disturbances[20,21], and that encompasses most of the factors that affect plant growth; and (2) the effects of biodiversity on ecosystem functioning come from species interactions, the magnitude and direction of interactions of which shift along stress gradients[14,22]
A decrease in the complementarity effect should weaken the positive correlation between biodiversity and productivity; we may expect the positive biodiversity–productivity relationship to vary along stress or productivity gradients in response to changes in species interactions[10,16,26]
Summary
The effect of biodiversity on primary productivity has been a hot topic in ecology for over 20 years. A decrease in the complementarity effect should weaken the positive correlation between biodiversity and productivity; we may expect the positive biodiversity–productivity relationship to vary along stress or productivity gradients in response to changes in species interactions[10,16,26]. Complementarity in stressful environments might enhance the positive effect of biodiversity on productivity where average productivity is low This positive biodiversity–productivity relationship should gradually flatten out in more fertile environments, in which complementarity is less important[16]. If this is the case, biodiversity–productivity relationships should converge as plant biodiversity increases (Fig. 1a), and the spatial variation in primary productivity between different communities should be smaller at high vs low biodiversity. S is defined as 1/variability, where variability is a measure of the magnitude of spatial changes in an a b
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