Synthesis science can take many forms, and collaborative networks of researchers performing identically replicated experiments across vast spatial scales is becoming an increasingly established form of synthesis in ecology. Distributed experiments can test theory and deepen our understanding of the biotic and abiotic contingencies in environmental responses to experimentally altered environments. This approach has not always been common: a few networks, including the Nutrient Network, have worked to develop the scientific and social elements of large group experimental collaboration. Nutrient Network, in particular, is using synthesis science to experimentally test ecological theory to better predict the resilience of the world’s grasslands to global change.
This global collaborative research group used identical methods to experimentally manipulate multiple nutrients (N, P, K and micronutrients) and exclude vertebrate herbivores from >100 sites around the world. By measuring plot-scale plant species richness and abundance as well as annual net plant production across continents and over the course of a decade, we tested spatial and temporal drivers of variability and factors maintaining resilience in diversity and productivity.
Results/Conclusions
Across these sites, nutrient addition increased the synchrony of species in diverse grasslands, reducing the stabilizing effect of diversity on grassland primary production. Compositional turnover of grassland communities through time in response to nutrients and consumers increased strongly with site-level spatial variability of species composition in the pre-treatment environment. Elevated nutrients also increased the importance of inter-annual climate fluctuations for species turnover and invasion and increased the responsiveness of biomass production to drought conditions.
These results, arising from multi-continent, long-term replicated sampling provide powerful and unique tests of the generality of ecological theory. This synthetic experimental work is demonstrating that grasslands experiencing rapid, concurrent increases in nutrient supply and droughts will likely experience the greatest loss of resilience in the coming decades. Further, temporal species turnover in response to perturbations depends on site-level spatial variability, demonstrating the deep interlinkages between spatial and temporal variability. A decade of Nutrient Network synthetic, experimental science has demonstrated that this approach is not only a viable tool for ecology, but also can accelerate the generation of new scientific knowledge via novel experimental tests of the generality and contingencies of ecological theory.