Precipitation patterns and N availability legacy govern microbial response to rewetting in a plant-soil system

Climate change models predict shifts in the frequency and magnitude of rain events (precipitation patterns). We studied how precipitation history shapes microbial community responses to rewetting and how these effects depend on N status. Twelve weeks of contrasting precipitation and N input left a legacy effect by shaping present (DNA-based) and potentially active (rRNA-based) bacterial and fungal communities. This legacy effect determined the microbial response to rewetting, as demonstrated by differences in the post-wet potentially active bacterial and fungal communities as well as the flux of soil-emitted CO2 over a 29-h period. Despite contrasting effects of precipitation and N input history on fungal:bacterial ratio and microbial community composition, the timing of the potentially active bacterial and fungal response to rewetting was not altered. Thus, regardless of precipitation or N input history, potentially active bacteria responded with a small shift in community composition within 1 h of rewetting but did not change further for the remaining 28 h analyzed. The potentially active fungi did not respond to rewetting within 29 h. Even though more extreme fluctuations in soil moisture changed soil microbial community composition, the short-term response of microbial communities to rewetting was conserved. Soil CO2 efflux upon rewetting was higher from systems with a history of frequent precipitation and underline the role of plants in drying-rewetting processes. We suggest that shifts in the fungal:bacterial ratio, as well as N-cycling potentials, may have consequences on food web stability and soil biogeochemical cycling.

Automated summary

This study found that precipitation history has an impact on the microbial community's response to rewetting, which is related to the nitrogen status. Regardless of precipitation or nitrogen input history, active bacteria showed a small shift in community composition within 1 hour of rewetting, but did not change further for the remaining 28 hours analyzed. Active fungi did not respond to rewetting within 29 hours. These findings are important for understanding the short-term response of soil microbial communities and their effects on food web stability and soil biogeochemical cycling.