Drought history affects grassland plant and microbial carbon turnover during and after a subsequent drought event

Drought periods are projected to become more severe and more frequent in many European regions. While effects of single strong droughts on plant and microbial carbon (C) dynamics have been studied in some detail, impacts of recurrent drought events are still little understood. We tested whether the legacy of extreme experimental drought affects responses of plant and microbial C and nitrogen (N) turnover to further drought and rewetting. In a mountain grassland we conducted a 13C pulse-chase experiment during a naturally occurring drought and rewetting event in plots previously exposed to experimental droughts, and in ambient controls. After labelling we traced 13C below-ground allocation and incorporation into soil microbes using phospholipid fatty acid (PLFAs) biomarkers. Drought history had no effects on the standing shoot and fine root plant biomass. However, plants with experimental drought history displayed decreased shoot N concentrations, and increased fine root N concentrations...