【目的】揭示干旱对杨树人工林土壤微生物生物碳量(C)、氮(N)、磷(P)及其生态化学计量特征的影响。为深入了解未来全球干旱背景下杨树人工林土壤C、N、P生物地球化学循环,以及人工林的合理经营提供理论依据。【方法】以江苏省东台林场美洲黑杨(Populus deltoides)人工林为对象,设置自然降水(CK)、穿透雨减少30%(D1)和穿透雨减少50%(D2)3种处理,探讨土壤微生物生物量碳(MBC)、氮(MBN)、磷(MBP)及其生态化学计量特征(记为MBC/MBN、MBC/MBP、MBN/MBP)对干旱处理的响应,分析其与土壤理化性质之间的关系。【结果】①干旱处理显著降低了土壤MBC、MBN、MBP含量,D2处理较对照MBC、MBN、MBP分别降低了16.09%、22.60%、32.49%;干旱处理显著增加了MBC/MBN和MBC/MBP,与CK相比,D2处理两个比值分别提高了10.33%、25.15%,但干旱处理对MBN/MBP的影响不显著。②土壤MBC、MBN、MBP含量均有季节性差异,变化范围分别为344.67~500.12、45.21~63.22和15.33~23.48 mg/kg,在夏、秋两季,其含量均较低,而冬、春两季,其含量上升到较高水平,而土壤MBC/MBN和MBC/MBP的季节变化与之完全相反,MBN/MBP没有明显的季节变化。③与对照相比,干旱处理显著降低了土壤铵态氮($\mathrm{NH}_{4}^{+}-\mathrm{N}$)、可溶性有机碳(DOC)、有效磷(AP)含量和含水率(SWC),分别降低了68.81%、32.77%、29.87%和11.05%;而干旱处理后,土壤pH升高、硝态氮($\mathrm{NO}_{3}^{-}-\mathrm{N}$)含量增加,分别增加了1.51%和194.34%。相关性分析表明,土壤MBC、MBN、MBP与SWC和全氮(TN)含量呈极显著正相关,与土壤有机碳(SOC)、$\mathrm{NO}_{3}^{-}-\mathrm{N}$含量和碳氮比(C/N)呈显著或极显著负相关。土壤MBC/MBN、MBC/MBP、MBN/MBP与$\mathrm{NO}_{3}^{-}-\mathrm{N}$含量和C/N呈显著或极显著正相关,与SWC和TN含量呈显著或极显著负相关。【结论】干旱显著影响了杨树人工林土壤微生物生物量C、N、P含量及其生态化学计量特征,进而对土壤养分平衡和循环过程产生影响。

【Objective】This study aimed to reveal the effects of drought on soil microbial biomass carbon (C), nitrogen (N), and phosphorus (P), as well as their ecological stoichiometric characteristics in poplar plantations. We also aimed to understand the soil C, N, and P biogeochemical cycles in poplar plantations under a future global drought scenario and provide a theoretical basis for the rational management of these plantations.【Method】Soil microbial biomass C (MBC), N (MBN) and P (MBP), along with their ecological stoichiometric characteristics (i.e., MBC/MBN, MBC/MBP, and MBN/MBP), and soil physicochemical properties, were examined in a poplar plantation (Populus deltoides) at Dongtai Forest Farm, Jiangsu Province, China. Three treatments were established in this study, control (CK), 30% throughfall reduction (D1), and 50% throughfall reduction (D2).【Result】(1) Soil MBC, MBN, and MBP were significantly reduced under drought conditions compared to the control, with reductions of 16.09%, 22.60%, and 32.49%, respectively, for the D2 treatment. Both MBC/MBN and MBC/MBP were significantly increased under drought conditions, with increases of 10.33% and 25.15%, respectively, in the D2 treatment, while soil MBN/MBP ratios did not change significantly. (2) Soil MBC, MBN and MBP showed significant seasonal variations, ranging from 344.67 to 500.12 mg/kg, 45.21 to 63.22 mg/kg, and 15.33 to 23.48 mg/kg, respectively. MBC, MBN, and MBP contents were lower in summer and fall than in winter and spring. In contrast, seasonal variations in MBC/MBN and MBC/MBP showed opposite trends to those of MBC, MBN, and MBP, while seasonal variations in MBN/MBP were not significant. (3) Compared with the control, drought treatments significantly reduced $\mathrm{NH}_{4}^{+}-\mathrm{N}$, dissolved organic carbon (DOC), available phosphorus (AP), and soil water content (SWC) by 68.81%, 32.77%, 29.87%, and 11.05%, respectively. Drought treatments increased soil pH and $\mathrm{NO}_{3}^{-}-\mathrm{N}$ content by 1.51% and 194.34%, respectively. Correlation analyses showed that soil MBC, MBN, and MBP had highly significant positive correlations with SWC and total nitrogen (TN) and significant or highly significant negative correlations with SOC, $\mathrm{NO}_{3}^{-}-\mathrm{N}$ content, and the total carbon to nitrogen ratio (C/N). Soil MBC/MBN, MBC/MBP, and MBN/MBP showed significantly or highly significant positive correlations with $\mathrm{NO}_{3}^{-}-\mathrm{N}$ and C/N and significant or highly significant negative correlations with SWC and TN content.【Conclusion】Drought significantly affected soil microbial C, N, and P and their ecological stoichiometric characteristics in poplar plantations, potentially altering the soil nutrient balance and cycling in these plantations.