Legacy effects of contrasting water and N-availability patterns on plant-microbial response to rewetting
2019
Barnard, Romain | Engelhardt, Ilonka
Shifts in frequency and magnitude of rain events may affect plant physiology and soil microbial activity. We aimed to determine how precipitation history shapes the response dynamics of soil microbial communities to rewetting, as well as plant-microbial competition for N, and how the N status of the system may modulate the effects of precipitation regime. The legacy effects of 12 weeks of contrasting precipitation and N inputs was assessed in wheat mesocosms. The legacy effects on the response to rewetting of potentially active (rRNA-based) bacterial and fungal communities was then documented over 29h, by sequencing phylogenetic marker genes, and following the dynamics of plant-microbial coupling and competition for N using 13C-CO2 and 15N-NH4 labeling. Despite contrasting effects of precipitation and N input history on plant physiology, fungal:bacterial ratio, microbial communities and C availability, the dynamics of the potentially active microbial response to rewetting was not altered. A history of favorable conditions for the plant increased its overall competitiveness for N over microorganisms and stimulated soil CO2 efflux upon rewetting (although not modulated by N availability). By altering plant-microbial C and N dynamics and reducing soil C sequestration potential, more extreme fluctuations in soil moisture may affect future ecosystem functioning.
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