Study On Soil Organic C,N And Enzyme Activity Characteristics With Different Ecological Restoration Patterns In Desert Land Of Northwestern Sichuan,China

Alpine grassland,located on the eastern Qinghai-Tibetan Plateau,is the largest area alpine wetland and headwaters of Yangtse Rive and Yellow River,and plays an important role in eco-environment security in China.Since 1990s,because of global warming,overgrazing,wind erosion,Alpine grassland appears desertification in some areas and seriously influences the sustainable development of the economy and the eco-safety.It has become an urgent environmental problem of desertification control.Ecological restoration is a key method to the prevent and control of land desertification,and the suitable vegetation restoration patterns is very importance for maintain and restore desert grassland ecosystem.Soil organic carbon,nitrogen and enzyme activity is the key indicators of soil quality and soil ecological environment.It helpful assessment of ecological restoration of different restoration patterns and fertility restoration mechanism and provides the theoretical basis for the further research of soil fertility restorative effects technology and practical operation.In this paper,three ecological restoration measures including natural restoration(WLCD),sowing forage grasses(RGCD),and mixed sowing oat and forage grasses(YMCD)had been carried out for ecological restoration of fencing and setting sand-barriers desertified land,and the original desertification grassland with no restoration had been selected as control site(CK).and we studied in the process of desertification of grassland ecological restoration soil organic caobon,nitrogen and enzyme activity on 0-60 cm soil layer.The results showed that:(1)Afert 3 years' ecological reatoration,different ecological patterns all significant improved in vegetation characters,rule of YMCD>RGCD>WLCD>CK.Compared with CK,vegetation coverage of YMCD,RGCD,WLCD incresed 74.07%,48.47%and 21.22%,respectively.Plant height of YMCD,RGCD,WLCD were higher 19.35,12.09,2.31 cm.Biomass of YMCD,RGCD,WLCD were increased by 9.87,6.32,1.94 times in aboveground and 13.86,9.58,2.04 times in underground.(2)Three types of ecological restoration measures can discrease the summer surface temperature,increase the water-holding capacity.Three years later,summer surface temperature of YMCD,RGCD,WLCD is 23.0,28.4,39.5 0C,was significantly lower than CK(41.2 ?).Water content change trend is YMCD>RGCD>WLCD>CK.Compared with CK,water content of YMCD,RGCD,WLCD increased 2.10%?1.81%and 0.79%.But the difference of soil bulk density and pH value were not significant.(3)The contents of soil organic carbon(SOC)and active organic carbon fractions had significant difference under different ecological restoration patterns,and the rule is YMCD>RGCD>WLCD>CK.The incresaced rate of SOC and active organic carbon were most significant in 0-20 cm soil layer.Compared with the CK,the contents of SOC,easily organic carbon,dissolved organic carbon,particulate organic carbon,potential mineralized carbon,microbial biomass carbon of YMCD were increased by 146.10%,146.10%,146.10%,83.47%,60.22%,111.09%in 0-20 cm soil layer,respectively.There had significant difference in 20?40 cm layer,but no significant difference in 40?60 cm layer.(4)Three ecological restoration patterns were significantly improved soil nitrogen accumulation and the change rule is YMCD>RGCD>WLCD>CK.Compared with CK,the contents of soil total nitrogen(TN),available nitrogen,ammonium nitrogen,nitrate nitrogen,potential mineralized nitrogen,microbial biomass nitrogen in 0-20 cm layer were increased by 203.22%,112.97%,114.83%,151.12%,72.97%,119.37%.There had significant difference in 20?40 cm layer,but no significant difference in 40?60 cm layer.(5)The enmyze activity of cellulase,sucrase,amylase,polyphenol oxidase,urease,protease,nitrate reductase showed the rule of YMCD>RGCD>WLCD>CK under different ecological restoration model.Compared with CK,the enzyme activity of cellulase,sucrase,amylase,polyphenol oxidase,urease,protease,nitrate reductase of YMCD were increased by89.93%,269.75%,58.60%,61.39%,53.01%,52.95%,179.25%in 0?20 cm layer.There had significant difference in 20?40 cm layer,but no significant difference in 40?60 cm layer.The result suggeted that three ecological restoration patterns significant improved soil organic carbon and active fraction,nitrogen,enzyme activity,especially the pattern of mixed sowing oat and forage grasses with the help of fencing and setting sand-barriers.