Articles | Volume 2, issue 4
SOIL, 2, 565–582, 2016

Special issue: Soil science in a changing world: contributions of soil science...

SOIL, 2, 565–582, 2016

Review article 01 Nov 2016

Review article | 01 Nov 2016

Soil fauna: key to new carbon models

Juliane Filser1, Jack H. Faber2, Alexei V. Tiunov3, Lijbert Brussaard4, Jan Frouz5, Gerlinde De Deyn4, Alexei V. Uvarov3, Matty P. Berg6, Patrick Lavelle7, Michel Loreau8, Diana H. Wall9, Pascal Querner10, Herman Eijsackers11, and Juan José Jiménez12 Juliane Filser et al.
  • 1Center for Environmental Research and Sustainable Technology, University of Bremen, General and Theoretical Ecology, Leobener Str. – UFT, 28359 Bremen, Germany
  • 2Wageningen Environmental Research (Alterra), P.O. Box 47, 6700 AA Wageningen, the Netherlands
  • 3Laboratory of Soil Zoology, Institute of Ecology & Evolution, Russian Academy of Sciences, Leninsky prospekt 33, 119071 Moscow, Russia
  • 4Dept. of Soil Quality, Wageningen University, P.O. Box 47, 6700 AA Wageningen, the Netherlands
  • 5Institute for Environmental Studies, Charles University in Prague, Faculty of Science, Benátská 2, 128 43 Praha 2, Czech Republic
  • 6Vrije Universiteit Amsterdam, Department of Ecological Science, De Boelelaan 1085, 1081 HV Amsterdam, the Netherlands
  • 7Université Pierre et Marie Curie, Centre IRD Ile de France, 32, rue H. Varagnat, 93143 Bondy CEDEX, France
  • 8Centre for Biodiversity Theory and Modelling, Station d'Ecologie Théorique et Expérimentale, UMR5321 – CNRS & Université Paul Sabatier, 2, route du CNRS, 09200 Moulis, France
  • 9School of Global Environmental Sustainability & Dept. Biology, Colorado State University, Fort Collins, CO 80523-1036, USA
  • 10University of Natural Resources and Life Sciences, Department of Integrated Biology and Biodiversity Research, Institute of Zoology, Gregor-Mendel-Straße 33, 1180 Vienna, Austria
  • 11Wageningen University and Research Centre, P.O. Box 9101, 6700 HB Wageningen, the Netherlands
  • 12ARAID, Soil Ecology Unit, Department of Biodiversity Conservation and Ecosystem Restoration, IPE-CSIC, Avda. Llano de la Victoria s/n, 22700 Jaca (Huesca), Spain

Abstract. Soil organic matter (SOM) is key to maintaining soil fertility, mitigating climate change, combatting land degradation, and conserving above- and below-ground biodiversity and associated soil processes and ecosystem services. In order to derive management options for maintaining these essential services provided by soils, policy makers depend on robust, predictive models identifying key drivers of SOM dynamics. Existing SOM models and suggested guidelines for future SOM modelling are defined mostly in terms of plant residue quality and input and microbial decomposition, overlooking the significant regulation provided by soil fauna. The fauna controls almost any aspect of organic matter turnover, foremost by regulating the activity and functional composition of soil microorganisms and their physical–chemical connectivity with soil organic matter. We demonstrate a very strong impact of soil animals on carbon turnover, increasing or decreasing it by several dozen percent, sometimes even turning C sinks into C sources or vice versa. This is demonstrated not only for earthworms and other larger invertebrates but also for smaller fauna such as Collembola. We suggest that inclusion of soil animal activities (plant residue consumption and bioturbation altering the formation, depth, hydraulic properties and physical heterogeneity of soils) can fundamentally affect the predictive outcome of SOM models. Understanding direct and indirect impacts of soil fauna on nutrient availability, carbon sequestration, greenhouse gas emissions and plant growth is key to the understanding of SOM dynamics in the context of global carbon cycling models. We argue that explicit consideration of soil fauna is essential to make realistic modelling predictions on SOM dynamics and to detect expected non-linear responses of SOM dynamics to global change. We present a decision framework, to be further developed through the activities of KEYSOM, a European COST Action, for when mechanistic SOM models include soil fauna. The research activities of KEYSOM, such as field experiments and literature reviews, together with dialogue between empiricists and modellers, will inform how this is to be done.

Short summary
Soils store more than 3 times as much carbon than the atmosphere, but global carbon models still suffer from large uncertainty. We argue that this may be due to the fact that soil animals are not taken into account in such models. They dig, eat and distribute dead organic matter and microorganisms, and the quantity of their activity is often huge. Soil animals affect microbial activity, soil water content, soil structure, erosion and plant growth – and all of this affects carbon cycling.