Ecosystem Carbon and Soil Biodiversity

Abstract

Soils harbor a great diversity and abundance of soil biota, but because it is mostly invisible to our naked eye we are only just starting to discover it. This is not surprising given the estimated diversity of up to 106 species of bacteria per g of soil. The soil biota play key roles in ecosystem functions and hence in ecosystem services provided to humans, such as sustaining primary productivity through recycling plant nutrients and pest control. Soil biodiversity in turn depends on plants, directly through the influence by living plants and indirectly by after-life effects of dead plants, as primary producers provide energy and nutrients and create soil habitats. The soil food web (comprising bacteria, actinomycetes, fungi, soil fauna) itself represents only about 2 % of the total organic soil carbon yet it is central to soil carbon (C) sequestration through its impact on soil C turnover and stabilization by chemical and physical processes. However, how much or which soil biodiversity is needed to promote soil C sequestration remains an open question, yet key to develop management strategies for promoting soil C sequestration and biodiversity. Soils are of major importance in terms of ecosystem C given that terrestrial ecosystems contain more than 2,100 Pg organic C globally of which 1,500 Pg is located in soil. Moreover soils can serve as C source, i.e. C loss, or C sink, i.e. C sequestration in soil, and this balance is strongly dependent on soil management and soil biodiversity. Here we provide an overview of the current knowledge on the interdependency of soil biodiversity and ecosystem/soil C through interactions with primary producers. Overall most studies found that soil functional composition rather than species richness per se regulates soil C sequestration, through promoting ecosystem nutrient use efficiency, soil (micro)aggregate formation and soil depth development.