Drivers of invertebrate community assembly during ecosystem restoration

Abstract

Introduction Ecosystems are complex multi-trophic systems, and successful restoration needs to consider the mechanisms that underpin the reestablishment of biotic interactions. Critical to supporting this is improved understanding of the ecological processes that govern community assembly. Here, we investigate invertebrate community assembly within restoring calcareous grasslands and broadleaved woodlands, two habitats that represent major targets for restoration efforts. Objectives This study investigates how top-down and bottom-up trophic interactions structure arthropod communities in restoring grasslands and woodlands. Methods We surveyed arthropod predators and herbivores across 53 grasslands and 59 woodlands undergoing restoration. Using Structural Equation Modeling, we assessed how community structure responds to local (site age, size, habitat structure, plant species richness, starting conditions, and ongoing management) and landscape drivers (amount of habitat in the surrounding landscape). Results Top-down processes were stronger drivers of community assembly, with large predatory arthropods shaping species richness in both habitats and abundance in grasslands. Interactions among arthropod guilds were always positive, suggesting facilitation rather than competition. Large predators were less diverse in larger grasslands but more abundant in larger woodlands. Vegetation structure was a critical factor in structuring arthropod communities in both habitats; only in woodlands did landscape composition have an effect. Conclusions Predator-mediated coexistence plays an underappreciated role in restoration, with vegetation complexity acting as a critical mechanism through which habitats mediate trophic interactions. Recognizing complex community processes like species interactions will improve the effectiveness of management strategies for creating functionally diverse habitats.