【目的】探究四川栗子坪国家级自然保护区森林土壤酶活性沿海拔梯度垂直变化特征,及其对土壤理化性质和生态化学计量比的响应机制。【方法】以自然保护区海拔1 800、2 100、2 400、2 700 m森林土壤为研究对象,研究土壤酶活性、土壤理化性质及生态化学计量比垂直分布特征,采用冗余分析、蒙特卡洛检验和逐步回归法分析土壤理化性质及生态化学计量比对土壤酶活性的影响。【结果】随海拔升高,土壤脲酶活性先减后增;蔗糖酶活性增加;酸性磷酸酶活性先增后减;过氧化氢酶活性减弱。海拔2 700 m土壤脲酶和蔗糖酶活性最大值分别为1.09和2.13 mg/(g·h);海拔2 400 m土壤酸性磷酸酶活性最大值0.97 mg/(g·h);海拔1 800 m土壤过氧化氢酶活性最大值3.41 mg/(g·h)。不同海拔森林土壤理化性质及生态化学计量比存在显著差异,且生态化学计量比对土壤酶活性有重要影响,其中非毛管孔隙度、毛管孔隙度、土壤容重、全氮、有机碳含量是土壤酶活性的重要影响因子(P<0.01)。此外,土壤碳磷比、毛管孔隙与非毛管孔隙比同土壤碳氮等环境因子组合也能较好解释土壤酶活性变化。【结论】海拔变化通过改变土壤理化性质和生态化学计量特征,驱动4种关键土壤酶活性的变化。该研究为自然保护区海拔梯度土壤酶活性变化规律及驱动因素分析提供理论支撑。

【Objective】This study aims to investigate, vertical variation characteristics of soil enzyme activities along an elevational gradient and their response mechanisms to soil physicochemical properties and ecological stoichiometric ratios in the forest ecosystems of Liziping National Nature Reserve, Sichuan.【Method】Forest soils at four distinct elevations (1 800, 2 100, 2 400 and 2700 m) within the reserve were investigated. We analyzed the vertical distribution patterns of soil enzyme activities, soil physicochemical properties, and ecological stoichiometric ratios. The effects of soil physicochemical properties and ecological stoichiometric ratios on soil enzyme activities were assessed using redundancy analysis (RDA), the Monte Carlo permutation test, and stepwise regression analysis.【Result】The soil urease activity initially decreased and then increased with rising elevation, sucrase activity increased, acid phosphatase activity increased initially and then decreased, and catalase activity decreased. The maximum urease (1.09 mg/(g·h)) and sucrase (2.13 mg/(g·h)) activities occurred at 2 700 m. The peak acid phosphatase activity (0.97 mg/(g·h)) was observed at 2 400 m, while the highest catalase activity (3.41 mg/(g·h)) was recorded at 1 800 m. Forest soil physicochemical properties and ecological stoichiometric ratios exhibited significant differences across the studied elevations. Ecological stoichiometric ratios exerted a significant influence on soil enzyme activities. Among the key factors identified, non-capillary porosity, capillary porosity, total nitrogen, organic carbon, and soil bulk density were significant influencing factors for soil enzyme activities (P<0.01). Furthermore, combinations of environmental factors, including the soil carbon-to-phosphorus ratio (C/P), the capillary porosity to non-capillary porosity ratio, along with soil carbon and nitrogen, provided good explanatory power for the observed variations in soil enzyme activities.【Conclusion】Altitude drives differential responses in the four key soil enzyme activities by altering soil physicochemical properties and ecological stoichiometric ratios. This study provides theoretical support for understanding the patterns and driving factors of soil enzyme activity variations along elevational gradients in nature reserves.