Abstract:

The aim of this study was to investigate the effects of different types of sand-fixing vegetation restoration on soil physico-chemical properties， soil enzyme activities， and herbaceous plant diversity. The control was bare mobile sand dunes （CK） and the four types of sand-fixing vegetation were Psammochloa villosa （SB）， Caragana korshinskii （N）， Corethrodendron scoparium （H）， and a mixture of C. korshinskii and C. scoparium （NH）. The results show that： 1） Compared with mobile sand dunes， the shrub sand-fixing modes （N， H， NH） increased the contents of soil organic carbon （SOC）， total nitrogen （TN）， and available phosphorus （AP）. The treatments were ranked， from highest AP content in soil to lowest， as follows： N>H>SB>NH>CK， with the AP content in C. korshinskii （N） plots （8.73 mg·kg?1） being 45.5% higher than that in CK. The five treatments were ranked， from highest TN content in soil to lowest， as follows： H>N>NH>SB>CK， with the TN content in C. scoparium （H） plots （0.20 g·kg?1） being 263% higher than that in CK. Meanwhile， the highest values of SOC content （1.51 g·kg?1） and carbon-to-nitrogen ratio （C/N，25.13） were in the mixed （NH） plots， and were 55.5% and 42.8% higher than their corresponding values in CK. 2） The highest activities of soil β-glucosidase and alkaline phosphatase were in the C. korshinskii （N） plots， and they were significantly higher （by 73.7% and 1315.1%， respectively） than their corresponding values in CK. The treatments were ranked， from highest activity of β-1，4-N-acetylglucosaminidase in soil to lowest， as follows： SB>NH>CK>H>N， with the highest activity in the P. villosa （SB） plots. The soil β-glucosidase activity was significantly correlated with pH， TN， and nitrogen-to-phosphorus ratio （N/P）， while β-1，4-N-acetylglucosaminidase activity was significantly positively correlated with soil pH. 3） The Pielou evenness index of vegetation was significantly lower in the P. villosa （SB） plots than in the shrub sand-fixing plots. The Simpson’s dominance index and Pielou evenness index of vegetation were significantly negatively correlated with soil β-1，4-N-acetylglucosaminidase activity. Moreover， this enzyme （R2=0.66， P=0.003） and the carbon-to-phosphorus ratio （R2=0.41， P=0.01） were identified as key factors affecting herbaceous plant diversity. In summary， different types of sand-fixing vegetation affected the diversity of herbaceous plants by regulating the carbon-to-phosphorus ratio and β-1，4-N-acetylglucosaminidase activity in soil. Among the different vegetation modes， the mixed mode and C. korshinskii played important roles in maintaining the carbon-nitrogen balance and improving the content of available phosphorus， respectively. The findings of this study provide a scientific basis for optimizing sand-fixing vegetation and for promoting the sustainability of desertification control projects.

Key words: species diversity, soil properties, soil enzymes, ecological restoration of sandy lands