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

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.