5种相思树和尾巨桉人工林土壤养分和酶活性特征

Characteristics of Soil Nutrient and Enzyme Activities in Plantations of Eucalyptus urophylla×E. grandis and Five Acacia Species

摘要:

为揭示固氮树种土壤养分转化的酶学机制，对固氮树种[厚荚相思（Acacia crassicarpa）、黑木相思（A. melanoxylon）、卷荚相思（A. cincinnata）、大叶相思（A. auriculiformis）和马占相思（A. mangium）]及非固氮树种尾巨桉（Eucalyptus urophylla×E. grandis）人工林的土壤养分含量、酶活性及其相关性进行研究。结果表明，相思林40~60 cm土层的pH均高于尾巨桉林；5种相思林土壤各土层的TP、TK含量均低于尾巨桉林，而20~40 cm土层的TC、TN含量均高于尾巨桉林，黑木相思林和马占相思林各土层的有效养分均显著高于尾巨桉林（P<0.05）。0~10 cm土层中，相思林的土壤酸性磷酸酶和纤维素酶活性均高于尾巨桉林，大叶相思林的土壤脲酶、蔗糖酶、纤维素酶和芳基硫酸酯酶活性显著高于尾巨桉林（P<0.05），卷荚相思林的土壤脲酶、纤维素酶、几丁质酶和淀粉酶活性显著高于尾巨桉林（P<0.05）。相关分析结果表明，土壤脲酶、蔗糖酶和几丁质酶活性与AP显著负相关（P<0.05），蔗糖酶和纤维素酶活性与NH₄⁺-N显著负相关（P<0.05），脲酶、纤维素酶、芳基硫酸酯酶与土壤TK显著负相关（P<0.05），几丁质酶活性与TN含量呈显著正相关（P<0.05），土壤淀粉酶活性与NH₄⁺-N呈显著正相关（P<0.05），过氧化氢酶活性与土壤TK含量呈显著正相关。可见，与尾巨桉人工林相比，在我国南方退化山地引种相思树可提高土壤关键酶的活性，对土壤有效养分具有明显改良作用，有利于退化地土壤的生态修复及人工林长期生产力的维持。

Abstract:

In order to reveal the enzymatic mechanism of soil nutrient transformation, the soil nutrient contents and enzyme activities in plantations, such as nitrogen-fixing tree species (Acacia crassicarpa, A. melanoxylon, A. cincinnata, A. auriculiformis, A. mangium) and non-nitrogen-fixing species (Eucalyptus urophylla×E. grandis) were studied, and their relationships were analyzed. The results showed that the pH in 40-60 cm soil of Acacia plantations were higher than that in E. urophylla×E. grandis plantation, which total P and K contents at all soil layers were lower than those in E. urophylla×E. grandis plantation, while total C and total N contents at 20-40 cm soil were high in Acacia plantations. Soil available nutrients contents were significantly higher in A. melanoxylon and A. mangium than those in E. urophylla×E. grandis plantation (P<0.05). Compared to E. urophylla×E. grandis plantation, the acid phosphatase and cellulase activities at 0-10 cm soil layer were high in Acacia plantations, which the activities of soil urease, sucrase, cellulase and aryl sulfatase were the highest in A. auriculiformis plantation (P<0.05); the activities of soil urease, cellulose, chitinase and amylase were the highest in A. cincinnata plantation (P<0.05). Correlation analysis revealed that the activities of soil urease, sucrase and chitinase were significantly negative to soil AP (P<0.05); the activities of soil sucrase and cellulase were signifi-cantly negative to soil NH₄⁺-N; the activities of soil urease, cellulase and aryl sulfatase were significantly negative to soil TK; the activities of soil chitinase were significantly positively to soil TN; the activities of soil amylase were significantly positively to soil NH₄⁺-N; the activities of soil catalase were significantly positively to soil TK. Therefore, compared to E. urophylla×E. grandis plantation, the introduced Acacia species to soil degraded mountains in southern China could improve key soil enzyme activities and soil available nutrients, which was beneficial to the eco-restoration of degraded soil and the maintenance of long-term productivity of plantations.