5种相思树和尾巨桉人工林土壤养分和酶活性特征

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(Eucalyptusurophylla×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40～60cm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(P0.05)。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(P0.05),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(P0.05)。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(P0.05),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(P0.05),几丁质酶活性与TN含量呈显著正相关(P0.05),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。

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

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.