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 a13C pulse-chase experiment during a naturally occurring drought and rewetting event in plots previously exposed to experimental droughts and in ambient controls (AC). After labelling, we traced13C below-ground allocation and incorporation into soil microbes using phospholipid fatty acid biomarkers.Drought history (DH) had no effects on the standing shoot and fine root plant biomass. However, plants with experimental DH displayed decreased shoot N concentrations and increased fine root N concentrations relative to those in AC. During the natural drought, plants with DH assimilated and allocated less13C below-ground; moreover, fine root respiration was reduced and not fuelled by fresh C compared to plants in AC.Regardless of DH, microbial biomass remained stable during natural drought and rewetting. Although microbial communities initially differed in their composition between soils with and without DH, they responded to the natural drought and rewetting in a similar way: gram-positive bacteria increased, while fungal and gram-negative bacteria remained stable. In soils with DH, a strongly reduced uptake of recent plant-derived13C in microbial biomarkers was observed during the natural drought, pointing to a smaller fraction of active microbes or to a microbial community that is less dependent on plant C.Synthesis. Drought history can induce changes in above- vs. below-ground plant N concentrations and affect the response of plant C turnover to further droughts and rewetting by decreasing plant C uptake and below-ground allocation. DH does not affect the responses of the microbial community to further droughts and rewetting, but alters microbial functioning, particularly the turnover of recent plant-derived carbon, during and after further drought periods.
Department of Microbiology and Ecosystem Science University of Vienna Althanstrasse 14A-1090 Vienna Austria; Present address: National Institute for Amazonian Research (INPA) Av. André Araujo 2936 Aleixo Manaus Amazonas CEP: 69067-375 Brazil.
Lucia
L
Fuchslueger
Institute of Ecology University of Innsbruck Sternwartestrasse 15 A-6020 Innsbruck Austria.
Michael
M
Bahn
Institute of Ecology University of Innsbruck Sternwartestrasse 15 A-6020 Innsbruck Austria.
Roland
R
Hasibeder
Department of Microbiology and Ecosystem Science University of Vienna Althanstrasse 14 A-1090 Vienna Austria.
Sandra
S
Kienzl
Institute of Ecology University of Innsbruck Sternwartestrasse 15 A-6020 Innsbruck Austria.
Karina
K
Fritz
Institute of Ecology University of Innsbruck Sternwartestrasse 15 A-6020 Innsbruck Austria.
Michael
M
Schmitt
Department of Microbiology and Ecosystem Science University of Vienna Althanstrasse 14 A-1090 Vienna Austria.
Margarete
M
Watzka
Department of Microbiology and Ecosystem Science University of Vienna Althanstrasse 14 A-1090 Vienna Austria.
Andreas
A
Richter
13C pulse labelling; below‐ground carbon allocation; drought; microbial community composition; nitrogen; phospholipid fatty acid; plant–soil (below‐ground) interactions; recovery; resilience