[Amelioration effect of sand-fixing Hedysarum fruticosum plantations on soil nutrient contents and biological activities].

With adjacent semi-moving dune as the control, this paper studied the effects of 5-, 10- and 22-year old Hedysarum fruticosum plantations on the nutrient status, microbial biomass, and enzyme activities at the soil depths 0-10, 10-20 and 20-30 cm. The results showed that with the establishment of H. fruticosum plantation on moving dune, soil C, N, P and K contents and biological activities increased obviously with the increasing age of the plantation, and the increment was much higher at 0-10 cm than at 10-20 and 20-30 cm. At 0-30 cm, soil C/N increased from 7.3 to 8.5, and microbial biomass C, N and P as well as the activities of urease, protease, saccharase, phosphomonoesterase, dehydrogenase, polyphenol oxidase and nitrate reductase all increased. Among the test enzyme activities, saccharase activity had the most significant increase, with its value at 0-10 cm being 49.7-284.5 times of the control. There were significant positive correlations between soil microbial biomass C, N and P and organic C, total N and total P, respectively, and between soil microbial biomass and enzyme activities.