General statistical scaling laws for stability in ecological systems.

Ecological stability refers to a family of concepts used to describe how systems of interacting species vary through time and respond to disturbances. Because observed ecological stability depends on sampling scales and environmental context, it is notoriously difficult to compare measurements across sites and systems. Here, we apply stochastic dynamical systems theory to derive general statistical scaling relationships across time, space, and ecological level of organisation for three fundamental stability aspects: resilience, resistance, and invariance. These relationships can be calibrated using random or representative samples measured at individual scales, and projected to predict average stability at other scales across a wide range of contexts. Moreover deviations between observed vs. extrapolated scaling relationships can reveal information about unobserved heterogeneity across time, space, or species. We anticipate that these methods will be useful for cross-study synthesis of stability data, extrapolating measurements to unobserved scales, and identifying underlying causes and consequences of heterogeneity.

We need more realistic climate change experiments for understanding ecosystems of the future.

Experiments that alter local climate and measure community- and ecosystem-level responses are an important tool for understanding how future ecosystems will respond to climate change. Here, we synthesized data from 76 studies that manipulated climate and measured plant community responses, and found that most climate change experiments do not correspond to model-projected climate scenarios for their respective regions. This mismatch constrains our ability to predict responses of plant biodiversity and ecosystem functions to climate change, and we conclude with suggestions for a way forward. See also the Commentary on this article by Muller et al., 26, e4-e5 and De Boeck et al.,26, e6-e7.

Integrating community assembly and biodiversity to better understand ecosystem function: the Community Assembly and the Functioning of Ecosystems (CAFE) approach.

The research of a generation of ecologists was catalysed by the recognition that the number and identity of species in communities influences the functioning of ecosystems. The relationship between biodiversity and ecosystem functioning (BEF) is most often examined by controlling species richness and randomising community composition. In natural systems, biodiversity changes are often part of a bigger community assembly dynamic. Therefore, focusing on community assembly and the functioning of ecosystems (CAFE), by integrating both species richness and composition through species gains, losses and changes in abundance, will better reveal how community changes affect ecosystem function. We synthesise the BEF and CAFE perspectives using an ecological application of the Price equation, which partitions the contributions of richness and composition to function. Using empirical examples, we show how the CAFE approach reveals important contributions of composition to function. These examples show how changes in species richness and composition driven by environmental perturbations can work in concert or antagonistically to influence ecosystem function. Considering how communities change in an integrative fashion, rather than focusing on one axis of community structure at a time, will improve our ability to anticipate and predict changes in ecosystem function.

Phosphorus resource partitioning shapes phosphorus acquisition and plant species abundance in grasslands.

Species diversity is commonly hypothesized to result from trade-offs for different limiting resources, providing separate niches for coexisting species1-4. As soil nutrients occur in multiple chemical forms, plant differences in acquisition of the same element derived from different compounds may represent unique niche dimensions5,6. Because plant productivity of ecosystems is often limited by phosphorus7, and because plants have evolved diverse adaptations to acquire soil phosphorus6,8, a promising yet untested hypothesis is phosphorus resource partitioning6,9,10. Here, we provided two different chemical forms of phosphorus to sown grassland mesocosms to investigate phosphorus acquisition of eight plant species that are common in European grasslands, and to identify subsequent patterns of plant abundance. For the first time, we show that the relative abundance of grassland plant species can be influenced by soil phosphorus forms, as higher abundance was linked to higher acquisition of a specific form of phosphorus. These results were supported by a subsequent isotope dilution experiment using intact grassland sods that were treated with different inorganic or organic phosphorus forms. Here, 5 out of 14 species showed greater phosphorus acquisition in the inorganic phosphorus treatment, and 4 in the organic phosphorus treatments. Furthermore, for the species used in both experiments we found similar acquisition patterns. Our results support the hypothesis of phosphorus resource partitioning and may provide a new mechanistic framework to explain high plant diversity in phosphorus-poor ecosystems6,11-13. As world biodiversity hotspots are almost invariably related to phosphorus limitation8,11,12, our results may thus also be key to understanding biodiversity loss in an era of ever-increasing nutrient enrichment14.