Precipitation changes altered soil heterotrophic respiration, but the underlying microbial mechanisms remain rarely studied. This study conducted three-year switchgrass ( L.) mesocosm experiment to investigate soil heterotrophic respiratory responses to altered precipitation. Five treatments were considered, including ambient precipitation (P0), two wet treatments (P+33 and P+50: 33% and 50% enhancement relative to P0), and two drought treatments (P-33 and P-50: 33% and 50% reduction relative to P0). The plant's aboveground biomass (AGB), soil organic carbon (SOC), total nitrogen (TN), microbial biomass carbon (MBC), heterotrophic respiration (R), biomass-specific respiration (R: respiration per unit of microbial biomass as a reciprocal index of microbial growth efficiency), and extracellular enzymes activities (EEAs) were quantified in soil samples (0–15 cm). Despite significantly different soil moisture contents among treatments, results showed no impact of precipitation treatments on SOC and TN. Increasing precipitation had no effect, but decreasing precipitation significantly reduced plant AGB. Relative to P0, P+33 significantly increased R by more than 3-fold and caused no changes in MBC, leading to significantly higher R ( < 0.05). P+33 also significantly increased hydrolytic enzyme activities associated with labile carbon acquisition () by 115%. The only significant effect of drought treatments was the decreased --cellobiosidase () and peroxidase () under P-33. Nonparametric analyses corroborated the strong influences of moisture and on the enhanced precipitation, which stimulated soil respiratory carbon loss, likely driven by both elevated hydrolase activities and reduced microbial growth efficiency. However, the less sensitive drought effects suggested potential microbial tolerance to water deficiency despite depressed plant growth. This study informs the likely decoupled impacts of microbes and plants on soil heterotrophic respiration under changing precipitation in the switchgrass mesocosm experiment.

中文翻译：

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柳枝稷中生态实验中降水变化对土壤异养呼吸和微生物活性的影响

降水变化改变了土壤异养呼吸，但潜在的微生物机制仍然很少研究。本研究进行了为期三年的柳枝稷（L.）中生态实验，以研究土壤异养呼吸对降水变化的反应。考虑了五种处理，包括环境降水量 (P0)、两种湿处理（P+33 和 P+50：相对于 P0 增强 33% 和 50%）以及两种干旱处理（P-33 和 P-50：33%）相对于 P0 减少 50%）。植物地上生物量（AGB）、土壤有机碳（SOC）、总氮（TN）、微生物生物量碳（MBC）、异养呼吸（R）、生物量特异性呼吸（R：每单位微生物生物量的呼吸作为倒数）微生物生长效率指数）和细胞外酶活性（EEA）在土壤样品（0-15 cm）中进行量化。尽管不同处理之间的土壤水分含量存在显着差异，但结果表明降水处理对 SOC 和 TN 没有影响。增加降水量没有影响，但减少降水量会显着降低植物 AGB。相对于 P0，P+33 使 R 显着增加 3 倍以上，但 MBC 没有变化，导致 R 显着升高 ( < 0.05)。P+33 还显着地将与不稳定碳获取相关的水解酶活性 () 提高了 115%。干旱处理唯一显着的影响是 P-33 下纤维二糖苷酶 () 和过氧化物酶 () 的降低。非参数分析证实了水分和降水增加的强烈影响，这刺激了土壤呼吸碳损失，这可能是由于水解酶活性升高和微生物生长效率降低所致。然而，对干旱影响不太敏感表明，尽管植物生长受到抑制，但微生物对缺水具有潜在的耐受性。这项研究揭示了柳枝稷中生态实验中降水变化下微生物和植物对土壤异养呼吸可能的解耦影响。