Can trait-based approaches model the resilience of soil microbial communities?

Soil microbial communities (microbiomes) are dynamic, responding continually to their surrounding environment.  These dynamics may relate to changes in the taxonomic/phylogenetic community structure as well as the functional capacity of the entire microbiome. This dynamism makes it challenging to define resilience for such ecosystems. Here, resilient communities are those able to adjust their taxonomic composition under environmental pulse or press stresses to maintain or restore a particular function.  Trait-based models typically assume trade-offs between life cycle strategies because of the resources required to enable different behaviours. An individual trait may be advantageous depending on the environmental conditions at a particular time and location. However, recent experiments addressing resilience in which soils were repeatedly exposed to stress cycles show soils developed the ability to maintain function despite a repeatedly imposed pulse stress. This suggests that a stress tolerance strategy operates in conjunction with other life cycle strategies. Here, we consider conceptual approaches to reconcile these findings – such as the inclusion of additional life strategies to represent further dimensions of soil community function and a community level trait-based approach that represents the dynamics of functional change in trait space. We also consider the challenge, pertinent to resilience modelling, of distinguishing between stress tolerance and the exposure to stress in heterogeneous soil; both aspects will affect the soil microbial community response, yet the latter could erroneously affect stress tolerance parameters in a trait-based model.