Ecosystem services provided by soil microorganisms

Ecosystem services are the contributions that ecosystems provide to human well-being. They arise from the interaction of biotic and abiotic processes, and refer specifically to the 'final' outputs or products from ecological systems. Soil harbours a large proportion of Earth's biodiversity, and provides the physical substrate for most human activities. Although soils have been widely studied and classified in terms of physical and chemical characteristics, knowledge of soil biodiversity and functioning are still incomplete. Soil organisms are extremely diverse and contribute to a wide range of ecosystem services that are essential to the sustainable functioning of natural and managed ecosystems. Microbial communities (mainly composed by Bacteria, Archaea and microfungi) are vital to soil ecosystem functioning. This is because they exist in enormous numbers and have an immense cumulative mass and activity. Most of the phenomena observed in the visible aboveground world are steered directly or indirectly by species, interactions, or processes in the belowground soil. In particular, being microbial communities involved in nutrient cycling and organic matter degradation, they can affect biodiversity and productivity of aboveground ecosystems. Microorganisms can have stimulating or inhibiting effects on plants by the release of metabolites with a varying range of activities. Microbial communities are the main responsible of soil homeostatic capabilities removing contaminants and providing key ecosystem regulating and supporting services such as soil fertility, resilience and resistance to different stress. This chapter aims at describing the contributions provided by soil microbial communities to different ecosystem services and their potential use as indicators of ecosystem functioning. Understanding ecosystem functioning and predicting responses to global changes calls for much better knowledge than we have today about microbial processes and interactions, including those with plants in the rhizosphere.