COS 253-5 - Long-term climate exerts legacies in microbial functional composition

Abstract: Historical climate conditions can influence current ecosystem processes and sensitivity to perturbation, resulting in legacy effects that can complicate global change predictions. Legacy effects in key fluxes such as soil respiration can be driven by the traits of the soil microbial community, especially those related to drought tolerance and resource use. Because long-term climate patterns affect soil microbial community structure and function, climate legacy effects on ecosystem functioning may partly result from the genomic traits underpinning microbial function. Assessing the functional composition of microbial communities, and how they are influenced by both past and current climate conditions, can help clarify mechanisms driving legacy effects in ecosystem processes.


Using shotgun metagenomics, we characterized the potential functional composition of the soil microbial community across a well-characterized rainfall gradient in Texas, USA, where persistent legacy effects on soil respiration were previously reported. The region experienced a multi-year severe drought, followed by drought release during an ENSO event, allowing us to assess how functional genes change upon recovery from drought across different climate histories. We hypothesized that the functional composition of soil microbial communities would vary across the gradient, with higher investment in drought resistance at the dry end of the gradient, and more investment in genes associated with resource acquisition at the wet end of the gradient. We found that the functional composition of genes differ across the rainfall gradient, and that the abundance of genes associated with functions such as substrate uptake and degradation increased with mean annual precipitation. This increase in genes associated with resource acquisition is consistent with faster carbon cycling in soils in wetter climates and may to contribute to functional legacies in these soils. Genes associated with stress tolerance traits such as osmolyte and biofilm production varied less consistently with climate. Ongoing work will assess whether differences in the genetic composition soil microbes relate to observed patterns in functioning, and how differences in microbial functional composition across ecosystems can help predict biogeochemical responses to climate change.