Plant-soil interactions in a changing world

Abstract

Evidence is mounting to suggest that the transfer of carbon through roots of plants to the soil plays a primary role in regulating ecosystem responses to climate change and its mitigation. Future research is needed to improve understanding of the mechanisms involved in this phenomenon, its consequences for ecosystem carbon cycling, and the potential to exploit plant root traits and soil microbial processes that favor soil carbon sequestration.

Figure 1.. Direct and indirect effects of climate change on soil microbial communities and feedback to the Earth’s carbon dioxide production

Direct effects include the influence on soil microbes and greenhouse gas production of temperature, changing precipitation, and extreme climatic events. For example, increased temperature can stimulate microbial activity and carbon dioxide production. Indirect effects result from climate-driven changes in plant productivity and vegetation structure, which alter soil physicochemical conditions, the supply of carbon to soil in the form of root exudates and litter, and the structure and activity of microbial communities involved in carbon cycling . Autotrophs, such as plants, can convert carbon dioxide into organic carbon, whereas heterotrophs do the opposite. DOC, dissolved organic carbon. Adapted from Bardgett et al., 2008 [2].

Figure 2.. Plant-trait framework for understanding linkages between plant traits, resource inputs to soil, the functional composition of the soil microbial community, and soil carbon sequestration

The schematic shows the interdependency of labile and recalcitrant litter inputs to soil, which drive abundances of different functional groups of the soil microbial community and their involvement in carbon sequestration. Labile inputs to soil of low carbon:nitrogen ratio from litter and root exudates favor saprophytic (feeding, absorbing or growing upon decaying matter) bacterial-dominated microbial communities that promote carbon mineralization, and hence carbon loss. In contrast, recalcitrant litter inputs with high carbon:nitrogen ratio and low nutrient availability favor saprophytic fungi and carbon allocation to symbiotic fungi and bacteria, which both promote carbon storage in soil. Solid lines indicate carbon and dotted lines indicate mineral nitrogen and phosphorus flow. Overall, the stability and storage of carbon in soil increases along the spectrum from saprophytic- to symbiotic-based cycling, as indicated on the lower arrow. AM, arbuscular mycorrhizal; ECM, ectomycorrhizal; EM, ericoid mycorrhizal; SOC, soil organic carbon. Adapted from De Deyn et al., 2008 [22].