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Climate change has led to more frequent and intense droughts. A better understanding of forest production under drought stress is critical for assessing the resilience of forests and their capacity to deliver ecosystem services under climate change. However, the direction and magnitude of drought effects on aboveground and belowground forest ecosystem components remain poorly understood. Here, we conducted a drought experiment including 30 % and 50 % throughfall reduction in a poplar plantation in the eastern coast of China to test how different drought intensities affected aboveground and fine root production. We further investigated the responses of soil physicochemical properties (e.g., soil moisture, soil pH, soil carbon, and soil nitrogen), and microbial properties (e.g., total microbial biomass, fungi:bacteria ratios, and Gram+:Gram- bacteria ratios) to drought. We found that the aboveground production decreased by 12.2 % and 19.3 % following 30 % and 50 % drought intensities, respectively. However, fine root production increased by 21.6 % and 35.1 % under 30 % and 50 % drought intensities, respectively. Moreover, all above- and belowground components exhibited stronger responses to 50 % compared with 30 % drought intensity. Our results provide some of the first direct evidence for simultaneous responses of forest above- and belowground production to moderate and intense droughts, by demonstrating that fine root production is more sensitive than aboveground production to both levels of drought stress., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The frequency and intensity of droughts worldwide are challenging the conservation of soil organic carbon (SOC) pool. Microbial necromass is a key component of SOC, but how it responds to drought at specific soil depths remains largely unknown. Here, we conducted a 3-year field experiment in a forest plantation to investigate the impacts of drought intensities under three treatments (ambient control [CK], moderate drought [30% throughfall removal], and intensive drought [50% throughfall removal]) on soil microbial necromass pools (i.e., bacterial necromass carbon, fungal necromass carbon, and total microbial necromass carbon). We showed that the effects of drought on microbial necromass depended on microbial groups, soil depth, and drought intensity. While moderate drought increased total (+9.1% ± 3.3%) and fungal (+13.5% ± 4.9%) necromass carbon in the topsoil layer (0-15 cm), intensive drought reduced total (-31.6% ± 3.7%) and fungal (-43.6% ± 4.0%) necromass in the subsoil layer (15-30 cm). In contrast, both drought treatments significantly increased the BNC in the topsoil and subsoil. Our results suggested that the effects of drought on the microbial necromass of the subsoil were more pronounced than those of the topsoil. This study highlights the complex responses of microbial necromass to drought events depending on microbial community structure, drought intensity and soil depth with global implications when forecasting carbon cycling under climate change., (© 2023 John Wiley & Sons Ltd.)

Terrestrial productivity underpins ecosystem carbon (C) cycling and multi-trophic diversity. Despite the negative impacts of drought on terrestrial C cycling, our understanding of the responses of above- and belowground productivity to drought remains incomplete. Here, we synthesized the responses of terrestrial productivity and soil factors (e.g., soil moisture, soil pH, soil C, soil nitrogen (N), soil C:N, fungi:bacteria ratio, and microbial biomass C) to drought via a global meta-analysis of 734 observations from 107 studies. Our results revealed that the productivity variables above- and belowground (i.e., net primary productivity, aboveground net primary productivity, belowground net primary productivity, total biomass, aboveground biomass, root biomass, gross ecosystem productivity, and net ecosystem productivity) were decreased across all ecosystems. However, drought did not significantly affect litter mass across all ecosystems, and the responses of above- and belowground productivity to drought were non-uniform. Furthermore, the responses of these productivity variables to drought were more pronounced with drought intensity and duration, and consistent across ecosystem types and background climates. Drought significantly decreased soil moisture, soil C concentrations, soil C:N ratios, and microbial biomass C, whereas it enhanced soil pH values and fungi:bacteria ratios. Moreover, the negative effects of drought on above- and belowground productivity variables were correlated mostly with the response of soil pH to drought among all soil factors. Our study indicated that litter biomass, which mostly represents productivity levels via traditional ecosystem models, was not able to predict the responses of terrestrial ecosystem productivity to drought. The strong relationship between the responses of soil pH and terrestrial productivity to drought suggests that the incorporation of soil pH into Earth system models might facilitate the prediction of terrestrial C cycling and its feedbacks to drought., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:, (Copyright © 2021 Elsevier B.V. All rights reserved.)

Tumor necrosis factor receptor-associated factor (TRAF) proteins play crucial roles in plant development and response to abiotic stress. Here, we present genetic evidence that SEVEN IN ABSENTIA 2 (SINA2), a TRAF-like family protein, is involved in abscisic acid (ABA)-related drought stress signaling in Arabidopsis. Gene expression, protein subcellular localization, protein-protein interaction, and a transient transcription dual-luciferase assay were performed. The drought tolerance of SINA2 loss-of-function mutants and SINA2-overexpressing plants was investigated. In Arabidopsis, SINA2 was significantly induced by ABA and drought treatment. The SINA2-YFP fusion protein was predominately localized in the nuclei and cytoplasm. Loss of function of SINA2 (sina2) reduced drought tolerance, whereas overexpression of SINA2 increased stomatal closure, decreased water loss, and therefore improved drought resistance in transgenic plants. Upon ABA treatment, expression of some key ABA- and stress-responsive genes decreased in the sina2 mutant, but increased in SINA2-overexpressing plants. Furthermore, SINA2 was induced in the ABA-deficient mutant by ABA, but not by drought stress. Thus, the drought response of SINA2 was ABA-dependent. ProSINA2::LUC expression in Arabidopsis protoplasts further revealed that ABA-responsive element (ABRE) binding (AREB) protein 1 (AREB1) AREB2 and ABRE-binding factor 3 (ABF3) might regulate SINA2 expression at the transcriptional level. Our results indicate that SINA2 functions as a positive molecular link between drought tolerance and ABA signaling in Arabidopsis., (© 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.)

• Drought increased enzyme activity C:N and fungi:bacteria ratios. • Microbial C and N use efficiencies increased under drought. • The threshold elemental ratio values were larger than the soil C:N ratio. Drought has been observed to decrease the accumulation of carbon (C) and nitrogen (N) in forest ecosystems. The microbial C use efficiency (CUE) and N use efficiency (NUE) are critical to elemental cycling in terrestrial ecosystems, which can be calculated by the C:N stoichiometry of soils, microbial biomass, and extracellular enzyme activities. However, little is known about how drought affects microbial CUE and NUE. We extracted soil samples at different depths (0–15 cm, 15–30 cm, and 30–45 cm) in forest stands that were subjected to 30% and 50% throughfall reduction manipulation experiments, in contrast to those obtained from stands that were left undisturbed from July 2019 to April 2020 in a poplar plantation of Eastern China. Under drought conditions, we found that the soil moisture, soil C:N ratio, and C- and N-acquiring enzyme activities decreased; however, the soil pH, microbial biomass C:N ratio, ecoenzymatic activity C:N ratio, and fungi:bacteria ratio increased. Microbial CUE and NUE, which were calculated based on these C:N stoichiometric ratios, also increased. These responses were similar at different soil depths across sampling dates. Our structural equation models indicated that drought-induced increases in CUE and NUE were driven by changes in the soil moisture, fungi:bacteria ratio, and ecoenzymatic activity C:N ratio. Our results suggested that decreases in soil moisture and increases in the ecoenzymatic activity C:N and fungi:bacteria ratios could stimulate microbial CUE and NUE. [ABSTRACT FROM AUTHOR]

• Fungi:bacteria ratio increased with drought stress. • Labile organic C and N contents influenced microbial communities greatly. • These responses kept consistent across different soil depths. Soil microbial communities are key to ecosystem processes in terrestrial ecosystems. Although droughts are projected to be more frequent with the intensifying effects of climate change, our understanding of the responses of soil microbial communities to drought remains incomplete. For this study, we employed 30% and 50% throughfall reduction manipulation experiments to simulate different drought intensities, and collected soil samples at three depths (0–15, 15–30 and 30–45 cm) for each season in a poplar plantation. We analyzed the physical and chemical properties of the soil samples (e.g., soil moisture, pH, total C, total N, and labile organic C and N contents represented by extractable organic C and N contents, microbial biomass C and N contents) and microbial communities, via phospholipid fatty acid (PLFA) and high-throughput sequencing methods, from November 2018 to August 2019. We found that drought significantly decreased soil moisture, the content of soil labile organic C and N, and total microbial biomass; however, it increased soil pH and microbial biomass C:N across all soil depths. Furthermore, fungi:bacteria and Gram+:Gram- bacterial ratios increased with drought treatments across all three soil depths. Drought reduced the relative abundance of Proteobacteria, but increased the relative abundance of Acidobacteria across the three soil depths. In contrast, drought had no significant influence on the relative abundance of fungal phyla. The changes in soil properties and microbial communities increased with drought intensity. Regression analysis demonstrated that changes in the total PLFA, fungi:bacteria and Gram+:Gram- bacterial ratios were significantly correlated with soil moisture, pH, and the soil labile organic C and N content. Redundancy analysis revealed that soil pH, extractable organic C and extractable organic N accounted for the majority of the variabilities in the bacterial communities. The patterns of fungal community structures in the drought treatment plots were not distinct from the control groups across three soil depths. Our results suggested that droughts induce significant increases in fungi:bacteria and Gram+:Gram- bacterial ratios in forest soils, primarily through changes in soil pH, moisture, and soil labile organic C and N content. [ABSTRACT FROM AUTHOR]