Soil food webs and climate change

Background/Question/Methods

Soil harbours a large part of the world’s biodiversity and governs processes that are regarded as globally important components in the cycling of materials, energy and nutrients. For example: a survey of arable soils show that the soil living biomass processes more than 50,000 kg of fresh organic material each year on a hectare basis. A rough approximation for the Netherlands indicates that, as a consequence, more than 20 Mt CO₂ is emitted to the atmosphere, which is almost half of the NL contribution to the Kyoto Protocol CO₂ reduction ambitions. This processing includes the decomposition of dead organic matter by the microbes, mostly bacteria and fungi, as well as the consumption and production rates in the soil community food web, including protozoa, nematodes, micro-arthropods such as mites and collembola, enchytraeids and earthworms. With its large diversity and complexity, it is the structure of the soil food web that governs the way in which processes alter under environmental change.

Results/Conclusions

Climate change may affect resource availability and productivity in ecosystems. In soils, productivity and food web structure are inextricably interrelated. We argue that the stability of the soil food webs is connected to the ‘balance’ between productivity and food web structure. We show the role of such balance in simple model food chains and in real complex food webs. For the latter we discuss key-components in food web structure, i.e. the lengths and weights of trophic interaction loops, and how these food web attributes provide an ecological as well as mathematical explanation of the response of food web structure to environmental change. Finally, we illustrate how dynamics in loop structure governs food web structure during ecosystem development in natural primary succession gradients.