MESOCLOSURES – increasing realism in mesocosm studies of ecosystem functioning

Abstract

Summary1. Experimental studies linking community composition to functioning are typically confined to small and closed micro-or mesocosms. Such restricted conditions may affect both species' biology and their environment. Yet, targeting simple features in the behaviour of species may circumvent these constraints. Focusing on ecological functions provided by dung beetles, we test whether large, open-top cages -MESOCLOSURES -will intercept the flight trajectories of beetles, thereby allowing manipulation of local community composition. 2. MESOCLOSURES were built in both tropical forest (Brazil) and temperate grasslands (Finland), thus testing their general efficiency. Within the respective environments, we varied different aspects of MESOCLOSURE design: in the tropical forest, we examined the impact of MESOCLOSURE dimensions on exclusion efficiency, whereas in the temperate grassland, we assessed the potential for selectively excluding and including community members by different mesh sizes. In the temperate environment, we also went from method to application, using MESOCLOSURES to relate community composition to functioning under two simulated grazing regimes. 3. MESOCLOSURES allowed efficient manipulation of dung beetle communities, maintaining dung beetle densities at intended levels in both temperate and tropical systems. In the tropics, the smallest cages (1 9 1 m) offered the highest contrast in beetle densities inside vs. outside of the fence, whereas the largest cages (9 9 9 m) offered the lowest. Nonetheless, densities inside cages never exceed one-fifth of those outside. At the temperate site, manipulations of community structure through mesh size yielded significant differences in functioning and suggested an interaction between small dung-dwelling species and large tunnelling species. Within cages, higher grazing was reflected in augmented dung removal. 4. We conclude that MESOCLOSURES can be effectively used to study dung beetle functions across habitats and latitudes. As applied insights, the present study adds resolution to the significance of different functional groups of dung beetles and shows that grazing pressure may have an important impact on the ecosystem functions that they provide. Overall, this study suggests that targeted manipulation of dispersal may offer new solutions for linking fauna to ecosystem functions with minimal impact on the processes measured.

The importance of species identity and interactions for multifunctionality depends on how ecosystem functions are valued

“…However, we found no evidence of functional dominance by the large, tunneling species G. stercorarius , although interactions between G. stercorarius and A. fossor were important for reducing greenhouse gas fluxes and increasing dung decomposition, as has been found in previous studies (Lähteenmäki et al. , Slade and Roslin ).…”

“…We also expected different species to modify the functional effect of each other (Lähteenmäki et al. ), and the functional efficiency of species to change with a change in the environment (Slade and Roslin ). Tunneling species ( G. stercorarius and A. erraticus ) are expected to contribute strongly to bioturbation of dung and soil, facilitating decomposition of dung, recycling of nutrients between dung and plants, and microbial activity (Slade et al.…”

Dung beetle species interactions and multifunctionality are affected by an experimentally warmed climate

“…General relationships between species diversity and ecological functioning have been attributed to sampling effects, with larger species pools being more likely to include functionally dominant species (Cardinale et al , Lefcheck et al ). Whether dung beetle communities also include functionally dominant species has been addressed by several recent experiments (Beynon et al , Nervo et al , Lähteenmäki et al , Slade et al ). Multiple lines of research have pointed to large, dung‐burying beetles being functionally dominant both in tropical (Larsen et al , Slade et al ) and temperate (Rosenlew and Roslin , Kaartinen et al , Nervo et al ) systems.…”

“…Importantly, these studies have generally considered only the single function of dung decomposition. However, several recent studies on other functions mediated by dung beetles have suggested that multiple functions might benefit from having several functional groups present (Penttilä et al , Lähteenmäki et al , Slade et al , Manning et al ).…”

“…Thus, while small beetles may be less important for dung decomposition, recent studies have suggested a role for them in sustaining other functions (Penttilä et al , Slade et al ). Moreover, tunnelling and dung‐dwelling species may also interact with each other to determining net ecosystem functioning (Lähteenmäki et al ).…”