THE PARADOX OF ENRICHMENT IN METAECOSYSTEMS.
Gounand, I., Mouquet N., Canard, E., Guichard, F., Hauzy, C. and Gravel, D. (2014).
The American Naturalist, 184, 752-763, doi:10.1086/678406
Key message : Here we study the effect of nutrient, detritus, producer, and consumer spatial flows,combined with changes in regional enrichment, on the stability of a metaecosystem model. We considered both spatially homogeneous and heterogeneous enrichment. We found that nutrient and detritus spatial flows are destabilizing, whereas producer or consumer spatial flows are either neutral or stabilizing. We noticed that detritus spatial flows have only a weak impact on stability. Our study reveals that heterogeneity no longer stabilizes well-connected systems when accounting for explicit representation of nutrient dynamics. We also found that intermediate consumer diffusion could lead to multiple equilibria in strongly enriched metaecosystems. Stability can emerge from a top-down control allowing the storage of materials into inorganic form, a mechanism never documented before. In conclusion, local enrichment can be stabilized if spatial flows are strong enough to efficiently redistribute the local excess of enrichment to unfertile ecosystems. However, high regional enrichment can be dampened only by intermediate consumer diffusion rates.
Multiple equilibria with intermediate consumer diffusion rates and high enrichment levels in homogeneous metaecosystems. (A), Areas of stability for the homogeneous case. Gray area, stable equilibria. Red area, unstable equilibria. Orange and purple areas have multiple equilibria. (B), Bifurcation diagram of consumer extreme densities (spatial average) according to regional fertility for the consumer diffusion rate dc=0.5 (dashed line in A). The orange equilibria are stable, the black unstable. (C-F) illustrate the two equilibria types for the pair of parameters. C and D show the dynamics of all the compartments. E and F show the relative densities of the different compartments.
OTHER TOPICS: Aesthetics of Biodiversity, Biodiversity & Ecosystem Functioning, Biogeography, Macroecology & Ecophylogenetics, Experimental Evolution,
Functional Biogeography, Functional Rarity, Metacommunities, Metaecosystems, Reviews and Synthesis, Trophic Biogeography & Metaweb