Increasing evidence suggests that community-level responses to human-induced biodiversity loss start with a decrease of interactions among communities and between them and their abiotic environment. The structural and functional consequences of such interaction losses are poorly understood and have rarely been tested in real-world systems. Here, we analysed how 5 years of progressive, size-selective exclusion of large, medium, and small vertebrates and invertebrates—a realistic scenario of human-induced defaunation—impacts the strength of relationships between above- and belowground communities and their abiotic environment (hereafter ecosystem coupling) and how this relates to ecosystem functionality in grasslands. Exclusion of all vertebrates results in the greatest level of ecosystem coupling, while the additional loss of invertebrates leads to poorly coupled ecosystems. Consumer-driven changes in ecosystem functionality are positively related to changes in ecosystem coupling. Our results highlight the importance of invertebrate communities for maintaining ecological coupling and functioning in an increasingly defaunated world.
Bibliographical noteFunding Information:
We would like to thank various employees and volunteers of the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) and the Swiss National Park for assistance with fence construction and maintenance, vegetation and soil sampling and processing. We thank Alan Haynes, Melanie Hodel, Ursina Raschein and Henk Duyts for their work in plant, microbe, soil arthropod and nematode community assessment, Bigna Stoffel, Vera Baptista, Anna Schweiger, Annatina Zingg and Seraina Cappelli for sorting roots, Roman Alther, Bieke Boden, Monika Carol Resch, Charlotte Schaller, Magdalena Steiner, Silvan Stöckli and Peter Wirz for sampling and sorting aboveground-dwelling invertebrates. We are grateful to Dieter Trummer for developing the prototype of our exclosures. We thank Pablo Hueso for his help with the artwork in Fig. 1. Jennifer Firn, Yann Hautier and Loïc Pellissier provided invaluable comments on earlier versions of this manuscript. This study was funded by the Swiss National Science Foundation, SNF grant no. 31003A_122009/1 and SNF grant no. 31003A_140939/1 to A.C.R. and M.S. R.O.-H. acknowledges funding from a Juan de la Cierva-Incorporación fellowship (IJCI-2014-21252).
© 2018, The Author(s).