Post-drought effects on the plant-microbe carbon transfer in a mountain meadow

Wien

2014

S. 27

Artikel aus einer ZeitschriftUnselbständiges Werk

200190150

Drought has been projected to become more frequent in many European regions. While there is growing evidence that drought can severely affect plant and microbial carbon dynamics it is still not clear if and how plant and microbial carbon dynamics recover from drought, and to which extent effects of drought persist and alter the response to subsequent dry conditions. To address these questions we took advantage of a multi-year rain-exclusion experiment on a mountain meadow in the Austrian Central Alps. During a dry period following rewetting after a severe experimental drought a 13C-pulse labelling experiment was conducted to trace post-drought effects on the transfer dynamics of recently plant assimilated carbon from plants to microbial phospholipid fatty acids (PLFAs). In post-drought plots the soil water content was still at a lower level, but the plant biomass was similar as in controls, exhibiting similar carbon but lower nitrogen concentrations. The 13C uptake in shoots of plants in the post-drought plots was reduced compared to controls reflecting decreased photosynthesis. Moreover, the allocation of recent C to fine roots and into fine root respiration was reduced. However, the earlier drought treatment induced no lasting effects on the microbial biomass and community structure. Nonetheless, 13C uptake of plant derived C into microbial groups was slower in post-drought plots, but surprisingly summed up to the same total amounts as in control plots. This indicates a disproportionately higher transfer of recent C to soil microbes. We conclude that in the studied mountain meadow severe drought could have lasting effects on plant C uptake and belowground allocation dynamics, while the soil microbial community is highly resilient and can thereby alter C dynamics in the plant-soil system.