Food web effects of topographic heterogeneity.
Larkin, Daniel*,1, Zedler, Joy1, 1 University of Wisconsin, Madison, WI
ABSTRACT- Ecological theory predicts that greater incorporation of habitat heterogeneity in restoration should enhance diversity and key functions. Topographic heterogeneity mediates hydrology and broadly impacts structure and function, from genetic to ecosystem scales. In arid-lands restoration, 10-20 cm deep pits collect water and function as nodes of biotic recovery. In intertidal wetlands, subtler variations (1-3 cm) are important due to frequent water level oscillations. While research on topographic heterogeneity in restoration is limited, higher trophic levels are in general underrepresented in the restoration literature. In a large-scale (8-ha) southern California experimental restoration site, we tested the role of topographic heterogeneity on restoration of salt marsh trophic function. Shallow pools were important for fishes because standing water suppressed vascular plant establishment and provided habitat and algal foods for aquatic invertebrate prey. Pools were a preferred microhabitat for fishes even when the entire marsh was inundated: California killifish (Fundulus parvipinnis) occurred in pools three times as often as in non-pool areas (p < 0.0001) during high tide marsh access opportunities. At a larger scale, areas with topographic heterogeneity in the form of replicate tidal creek networks supported 37% more frequent occurrence of longjaw mudsucker (Gillichthys mirabilis) than areas without creeks (p<<0.0001). We propose a conceptual model for tidal wetlands wherein creeks function as conduits that enhance connectivity between subtidal and intertidal habitat and pools serve as "oases" of elevated prey resources. Multiple forms of heterogeneity help to restore food webs by enhancing feeding opportunities for consumers.
Key words: topographic heterogeneity, restoration ecology, salt marsh
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