Ecosystem functioning in the landscape: a meta-ecosystem perspective

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The past half-century has seen significant advances in our understanding of the spatial distribution of biodiversity. The meta-population and meta-community concepts cemented our appreciation of the importance of regional dynamics and our understanding of population persistence and species co-existence in the landscape. The next conceptual boundary, the meta-ecosystem concept, promises to unveil the mechanistic links between community and ecosystem ecology. At the intersection between those two fields lays the key to a landscape perspective on biodiversity and ecosystem functioning. However, we are still lacking a comprehensive understanding of the community level constraints on ecosystem response to cross-ecosystem subsidy and spatial cascades. My long-term objectives are to develop a better understanding of the connections within and among ecosystems, to predict how and when perturbations are most likely to propagate via those spatial couplings, and eventually to predict biodiversity distribution and ecosystem functioning at landscape scales. My specific objectives in this proposal are to: 1) develop a better understanding of the contingencies driving the response of recipient ecosystems to cross-ecosystem subsidy; 2) develop a formal test of the spatial cascade concept; 3) extend the spatial cascade concept to develop and test a landscape perspective on cross-ecosystem subsidy. My working hypotheses are that a) biotic interactions will impose predictable constraints on the response of recipient ecosystem to cross-ecosystem subsidy and b) that both biotic interactions and landscape configuration, in turn, will modulate how effects propagate in the landscape (spatial cascade). To reach my objectives I will use a variety of experimental approaches coupled with field observations. In Project 1 I will use zooplankton mesocosms to disentangle the effect of varying cross-ecosystem subsidy (quantity, quality) on the recipient ecosystem along a gradient of community alteration. I will also quantify those natural variations in subsidy and their effects in temperate lakes across a whole landscape. In project 2 I will set a formal test of the spatial cascade concept by testing the effect of harvesting and increased temperature in the donor ecosystem on the dynamics and processes in the recipient ecosystem, using zooplankton mesocosms. I will also quantify spatial cascades at the terrestrial-aquatic boundary using temporal observational data. In project 3, I will use experimental landscapes with microbial microcosms to test the extent to which landscape structure can constraint spatial cascades by limiting the zone of influence of subsidized consumers. The proposed research program will participate in developing a landscape scale understanding of how perturbations can spatially cascade, how recipient ecosystem might respond to those changes and eventually help to predict spatial variations in biodiversity and ecosystem function.