title: Forest understory plant and soil microbial response to an experimentally induced drought and heat-pulse event: the importance of maintaining the continuum.
abstract: Drought duration and intensity are expected to increase with global climate change. How changes in water availability and temperature affect the combined plant-soil-microorganism response remains uncertain. We excavated soil monoliths from a beech (Fagus sylvatica L.) forest, thus keeping the understory plant-microbe communities intact, imposed an extreme climate event, consisting of drought and/or a single heat-pulse event, and followed microbial community dynamics over a time period of 28 days. During the treatment, we labeled the canopy with (13) CO2 with the goal of (i) determining the strength of plant-microbe carbon linkages under control, drought, heat and heat-drought treatments and (ii) characterizing microbial groups that are tightly linked to the plant-soil carbon continuum based on (13) C-labeled PLFAs. Additionally, we used 16S rRNA sequencing of bacteria from the Ah horizon to determine the short-term changes in the active microbial community. The treatments did not sever within-plant transport over the experiment, and carbon sinks belowground were still active. Based on the relative distribution of labeled carbon to roots and microbial PLFAs, we determined that soil microbes appear to have a stronger carbon sink strength during environmental stress. High-throughput sequencing of the 16S rRNA revealed multiple trajectories in microbial community shifts within the different treatments. Heat in combination with drought had a clear negative effect on microbial diversity and resulted in a distinct shift in the microbial community structure that also corresponded to the lowest level of label found in the PLFAs. Hence, the strongest changes in microbial abundances occurred in the heat-drought treatment where plants were most severely affected. Our study suggests that many of the shifts in the microbial communities that we might expect from extreme environmental stress will result from the plant-soil-microbial dynamics rather than from direct effects of drought and heat on soil microbes alone.
authors.affiliation: Institute for Landscape Biogeochemistry, Leibniz Centre for Agricultural Landscape Research (ZALF), 15374 Müncheberg, Germany.
authors.forename: Isabell
authors.initials: I
authors.lastname: von Rein
authors.affiliation: Institute for Landscape Biogeochemistry, Leibniz Centre for Agricultural Landscape Research (ZALF), 15374 Müncheberg, Germany.|Berlin-Brandenburg Institute of Advanced Biodiversity Research (BBIB), Altensteinstr 6, D-14195 Berlin, Germany.|Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstr 111, CH-8903, Birmensdorf, Switzerland.
authors.forename: Arthur
authors.initials: A
authors.lastname: Gessler
authors.affiliation: Institute for Landscape Biogeochemistry, Leibniz Centre for Agricultural Landscape Research (ZALF), 15374 Müncheberg, Germany.|Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Chemical Analytics and Biogeochemistry, Müggelseedamm 310, 12587 Berlin, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Premke
authors.affiliation: Centre for Carbon, Water and Food, Faculty of Agriculture & Environment, university of sydney, 380 Werombi Rd, Brownlow Hill, NSW 2570, Australia.
authors.forename: Claudia
authors.initials: C
authors.lastname: Keitel
authors.affiliation: Institute for Landscape Biogeochemistry, Leibniz Centre for Agricultural Landscape Research (ZALF), 15374 Müncheberg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Ulrich
authors.affiliation: Institute for Landscape Biogeochemistry, Leibniz Centre for Agricultural Landscape Research (ZALF), 15374 Müncheberg, Germany.
authors.forename: Zachary E
authors.identifier: 0000-0003-0090-7537
authors.initials: ZE
authors.lastname: Kayler
mesh_terms: D057231:Climate Change; D055864:Droughts; D065928:Forests; D006358:Hot Temperature; D012336:RNA, Ribosomal, 16S; D012987:Soil; D012988:Soil Microbiology
chemical_list: D012336:RNA, Ribosomal, 16S; D012987:Soil
keywords: 13CO2 pulse labeling; 16S rRNA next-generation sequencing; PLFAs; climate extremes; drought; forest understory; heat-pulse; microbial community structure; plant-soil-microbe carbon continuum