There are many studies on disentangling the responses of autotrophic (AR) and heterotrophic (HR) respiration components of soil respiration (SR) to long-term drought, but few studies have focused on the mechanisms underlying its responses. To explore the impact of prolonged drought on AR and HR, we conducted the 2-year measurements on soil CO2 effluxes in the 7th and 8th year of manipulated throughfall reduction (TFR) in a warm-temperate oak forest. Our results showed long-term TFR decreased HR, which was positively related to bacterial richness. More importantly, some bacterial taxa such as Novosphingobium and norank Acidimicrobiia, and fungal Leptobacillium were identified as major drivers of HR. In contrast, long-term TFR increased AR due to the increased fine root biomass and production. The increased AR accompanied by decreased HR appeared to counteract each other, and subsequently resulted in the unchanged SR under the TFR. Our study shows that HR and AR respond in the opposite directions to long-term TFR. Soil microorganisms and fine roots account for the respective mechanisms underlying the divergent responses of HR and AR to long-term TFR. This highlights the contrasting responses of AR and HR to prolonged drought should be taken into account when predicting soil CO2 effluxes under future droughts.

中文翻译：

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暖温带橡树林自养和异养呼吸对长期下降的不同反应的不同机制

关于土壤呼吸（SR）的自养（AR）和异养（HR）呼吸成分对长期干旱的反应有很多研究，但很少有研究关注其反应的机制。为了探索长期干旱对 AR 和 HR 的影响，我们在暖温带橡树林中对人工降雨量减少 (TFR) 的第 7 年和第 8 年对土壤 CO2 流出进行了 2 年的测量。我们的结果显示长期 TFR 降低 HR，这与细菌丰富度呈正相关。更重要的是，一些细菌分类群，如新鞘氨醇和诺兰克酸性微生物，以及真菌细杆菌被确定为 HR 的主要驱动因素。相反，由于细根生物量和产量的增加，长期 TFR 增加了 AR。伴随着 HR 降低的 AR 增加似乎相互抵消，随后导致 TFR 下 SR 不变。我们的研究表明 HR 和 AR 对长期 TFR 的反应方向相反。土壤微生物和细根解释了 HR 和 AR 对长期 TFR 不同反应的各自机制。这突出了在预测未来干旱下土壤 CO2 流出时应考虑 AR 和 HR 对长期干旱的不同反应。