The uncertainty of soil respiration under the influence of rainfall significantly affects the carbon flux in forest ecosystems. Thus, this study assessed the impact mechanism of aggregate changes on short-term forest soil microbial respiration under rainfall simulation. The response of short-term soil microbial respiration to the variation in aggregate distribution, carbon concentration in the aggregate particles, dissolved organic carbon (DOC), dry bulk density, volumetric water content, capillary porosity, and soil aeration in the forest soil was investigated by a self-developed rainfall simulation system under 50 and 80 mm/h rainfall treatments. The system ensured the controllability, continuity, and integrity of the analysis from soil erosion to soil respiration. A proportional decrease in large macroaggregates (>2 mm) and an increase in small macroaggregates (0.25–2 mm) were detected due to rainfall, leading to the release of coarse particulate organic matter in large macroaggregates and an enrichment in microaggregates within small macroaggregates. The splitting of macroaggregates increased the DOC content and decreased the porosity and aeration of the soil. The CO₂ flux decreased immediately after rainfall treatment, and it increased at 12 h after the end of 80 mm/h rainfall. Moreover, the soil immediately emitted CH₄ at the end of 80 mm/h rainfall. Large macroaggregates and DOC had positive conditional effects on respective CO₂ and CH₄ fluxes at the end of rainfall. The results indicate that short-term soil microbial aerobic respiration is mainly regulated by the remaining macroaggregate distribution immediately after rainfall. Moreover, short-term soil microbial anaerobic respiration is mainly mediated by the DOC and microaggregates released from large macroaggregates under soil water saturation. The study concludes that the uncertainty of short-term soil microbial respiration is mainly derived from the random fragmentation and redistribution of macroaggregates in the soil immediately after rainfall treatments.

中文翻译：

---

大团聚体破碎对雨后短期土壤微生物呼吸的物理影响机制

降雨影响下土壤呼吸的不确定性显着影响森林生态系统中的碳通量。因此，本研究评估了降雨模拟下团聚体变化对短期森林土壤微生物呼吸的影响机制。研究了短期土壤微生物呼吸对团聚体分布、团聚体颗粒中碳浓度、溶解有机碳 (DOC)、干容重、体积含水量、毛细管孔隙率和森林土壤通气性变化的响应通过自主研发的降雨模拟系统在 50 和 80 mm/h 降雨处理下。该系统确保了从土壤侵蚀到土壤呼吸的分析的可控性、连续性和完整性。大聚集体成比例减少（> 2 毫米）和由于降雨而检测到小的大团聚体（0.25-2 毫米）增加，导致大团聚体中粗颗粒有机物的释放和小团聚体中微团聚体的富集。大团聚体的分裂增加了 DOC 含量，降低了土壤的孔隙率和通气性。CO₂通量在降雨处理后立即下降，80 mm/h降雨结束后12 h开始上升。此外，在 80 毫米/小时的降雨结束时，土壤立即释放出 CH _{4 。}大型聚集体和 DOC 对各自的 CO ₂和 CH _{4有积极的条件影响}降雨结束时的通量。结果表明，短期土壤微生物有氧呼吸主要受降雨后剩余大团聚体分布的调节。此外，短期土壤微生物厌氧呼吸主要由土壤含水饱和度下大团聚体释放的 DOC 和微团聚体介导。该研究得出结论，短期土壤微生物呼吸的不确定性主要来源于降雨处理后土壤中大团聚体的随机破碎和重新分布。