Ecosystem multifunctionality in metacommunities.

Ecosystem multifunctionality, the simultaneous production of multiple ecosystem functions, depends on community diversity, composition, productivity, and spatial scale. In metacommunities, each of these community properties is affected by how species disperse between local patches to track environmental change. Here we use a consumer-resource metacommunity model of resource competition to show how dispersal affects the link between diversity, composition, and ecosystem multifunctionality. When species differ in their functional traits and environmental niche, metacommunity multifunctionality becomes highly dependent upon dispersal, which allows community diversity to be maintained when environmental conditions change. Dispersal promotes multifunctionality in two ways: (1) species sorting, whereby species track local environmental changes by shifting in space, thus preserving diversity and ensuring high biomass productivity, and (2) mass effects, whereby source-sink dynamics allow species to persist in suboptimal environments, thus increasing local diversity. Changing the rate at which species disperse affects the strength of these metacommunity processes, and so metacommunity multifunctionality exhibits a unimodal relationship with dispersal, peaking when dispersal is intermediate. Species-sorting dynamics also provide spatial insurance whereby compensatory dynamics stabilize the fluctuations of each function through time at the regional scale. However, this does not extend to the local scale, where species sorting results in high temporal variability for each function, even though the overall rates of multifunctionality are high. Our results suggest that metacommunity processes are important determinants of ecosystem multifunctionality, and thus effective management of multiple ecosystem functions requires consideration of landscape connectivity.