| Longnan mountainous area in southern Gansu province is located in the area where geological hazards occur frequently in China.Due to the influence of geological hazards and man-made destruction factors,the deterioration of local ecological environment has become more and more prominent.As an important means and content of protecting and restoring fragile ecological environment,vegetation restoration plays an important role in controlling soil erosion and restoring ecological environment,it has become one of the most important measures to improve and restore the local ecological environment.Based on field investigation and laboratory experiment analysis,the soil physicochemical properties and soil enzyme activity of four restored types?natural forest land,natural grassland,artificial forest land and artificial grassland?and control plot?bare land?in Wudu district of Longnan mountainous area in southern Gansu province were systematically studied,and the relationships between soil enzyme activity and soil physicochemical factors under natural restoration?natural forest land and grassland?and artificial restoration?artificial forest land and grassland?were also discussed,which was expected to provide a theoretical basis for further implementation of vegetation restoration.After research,this paper drew the following conclusions:?1?Different vegetation restoration types had different effects on soil physicochemical properties.Compared with other vegetation restoration types,the natural forest land had the smallest soil bulk density(1.14 g·cm-3)and the largest porosity?57.37%?,indicating that the soil of natural forestland had a higher capacity to retain water and fertilizer,which was beneficial to the improvement of soil condition.In addition,the contents of soil water content,organic carbon,total nitrogen,alkali-hydrolyzed nitrogen and available phosphorus in the natural vegetation restoration scheme were significantly higher than those in the artificial vegetation restoration scheme,indicating that natural vegetation restoration was more conducive to soil moisture retention and soil carbon,nitrogen and phosphorus accumulation.?2?The distribution characteristics of soil enzyme activities were different under different vegetation restoration types.The activities of soil?-glucosidase,urease and alkaline phosphatase in the soil were the strongest in natural forest land and the lowest in bare land in the study area.The average activities of soil?-glucosidase,urease and alkaline phosphatase in the natural vegetation restoration scheme were 8.98?g·g-1·h-1?16.73?g·g-1·h-11 and 63.37?g·g-1·h-1,respectively,which were significantly higher than those in the artificial vegetation restoration scheme(4.27?g·g-1·h-1?9.13?g·g-1·h-11 and 41.61?g·g-1·h-1,respectively).There was a certain correlation between different soil enzymes in the natural and artificial vegetation restoration schemes.There was a significant correlation between soil?-glucosidase activity and alkaline phosphatase activity in natural restoration scheme,while a high correlation between soil?-glucosidase activity and urease activity in artificial restoration scheme,indicating that soil enzymes had both specificity and synergy in the process of enzymatic catalysis.?3?The activity of soil enzymes was closely related to the role of soil physicochemical factors.In this study,soil enzyme activity and soil physicochemical properties showed a high correlation under natural and artificial vegetation restoration schemes.Soil organic carbon and total nitrogen were the most important factors influencing soil?-glucosidase activity.Alkali-hydrolyzed nitrogen and total nitrogen were the main factors influencing soil urease activity.Alkali-hydrolyzed nitrogen was the main factor influencing soil alkaline phosphatase activity.According to the results of redundancy analysis?RDA?,soil physicochemical factors explained 85.22%and80.21%of soil enzyme activity variation respectively under natural and artificial vegetation restoration schemes.The pH value,soil organic carbon,total nitrogen,alkali-hydrolyzed nitrogen and bulk density were the main factors influencing soil enzyme activity in natural restoration plots,while the main factors influencing soil enzyme activity in artificial vegetation restoration scheme were total nitrogen,pH value,alkali-hydrolyzed nitrogen,bulk density and soil moisture content. |
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