Figure 6
From: Edge effects reverse facilitation by a widespread foundation species
Incorporating edge effects into conceptual models of facilitation.
Conceptual model depicting how edge effects could drive spatial heterogeneity in habitat modification within the domain of a habitat-former. The heavy black lines indicate, for each of two habitat types, a previously described pattern in which increased habitat density or size of an aggregation cause greater amelioration of environmental stress59. Dotted lines indicate ambient stress levels outside the biogenic habitat. As explored here, habitat modification could exacerbate environmental stresses as well as mitigate them (thin solid lines). (A) Case of a vertical core through a mussel bed in which interior locations experience reduced temperatures via shading and poor heat conduction, while the bed surface encounters elevated temperatures compared to nearby bedrock, as small, dark shells heat rapidly under solar radiation. In this first scenario, only interior reductions in temperature will likely depend on the density or size of the mussel bed. (B) An alternative example in which a biogenic habitat again ameliorates and exacerbates environmental stress simultaneously, but both processes depend on habitat density or size. Here, the tendency for a stand of forest trees to slow wind speeds in its interior increases with the density or spatial extent of the stand. Likewise, the tendency for the forest stand to divert winds around it and therefore induce flow acceleration along its edges rises as the density and/or dimensions of the stand increases.
