Soil microbes and community coalescence

• Community coalescence may be a pervasive phenomenon in soils.
• Soil-intrinsic and external factors drive community coalescence events.
• Dedicated experiments will be important to study community coalescence.
• Global change may increase community coalescence in soils.
• Soil ecology stands to profit from considering community coalescence.

Community coalescence is a recently introduced term describing the interaction of entire communities and their environments. We here explicitly place the concept of community coalescence in a soil microbial context, exploring intrinsic and extrinsic drivers of such coalescence events. Examples of intrinsic events include the action of earthworms and the dynamics of soil aggregates, while extrinsic events are exemplified by tillage, flooding, litter-fall, outplanting, and the addition of materials containing microbial communities. Aspects of global change may alter the frequency or severity of coalescence events. We highlight functional consequences of community coalescence in soil, and suggest ways to experimentally tackle this phenomenon. Soil ecology as a whole stands to benefit from conceptualizing soil biodiversity in terms of dynamic coalescent microbial assemblages.