COS 77-2 - Climate legacy effects on dryland microbiomes: could microbial legacies slow plant recovery from drought?

Abstract: Climate projections for many regions include increased frequencies of decadal-long drought. Climate disruptions, such as droughts, commonly alter the composition of microbial assemblages, leaving a legacy of persistent changes that may drive the pace of ecosystem recovery. Dryland ecosystems may respond more strongly to chronic drought than mesic systems, but microbial responses to drought are understudied in drylands. Previous evidence shows that drought can negatively affect the abundance and diversity of dryland soil surface microbial communities (biocrusts). In other ecosystems, microbial ‘restorations’ can promote community recovery after disturbance. Therefore, we asked, can microbial restoration promote the recovery of plant communities and ecosystem functions following drought? We quantified the contributions of microbial communities with or without a history of drought after ending a seven-year chronic drought experiment in a Plains grassland in central New Mexico, USA. We reciprocally transplanted light cyanobacterial biocrusts between drought and control plots and added seeds of the dominant grass (blue grama,
Bouteloua gracilis

) to initiate plant recovery. We tracked biocrust community composition with 16S rRNA sequencing and biomass with chlorophyll
a

concentration to monitor success of the microbial transplants. To measure ecosystem recovery, we assessed seedling recruitment and harvested total plant biomass. Microbial transplants of biocrusts were successful, as shown by sequencing results. Restoration of control microbes increased seed recruitment post-drought by 34% relative to microbes with a drought history, indicating that microbial drought legacies slowed plant recovery. Additionally, when biocrusts were sterilized, blue grama had the lowest recruitment. Similarly, following harvest, blue grama biomass in plots recovering from drought was 63% greater when inoculated with control microbes in comparison to microbes with a drought legacy. Our findings demonstrate that successful transplantation of biocrusts after drought can aid in ecosystem recovery and could provide a management strategy for arid grasslands under climate disruption.