| Desert grassland is an important terrestrial ecosystem for animal husbandry production and ecological environment protection in northern China.It is also a fragile ecosystem,which is easily degraded by human activities and climate change.Reseeding is one of the effective measures for restoring degraded grassland,so it is of great scientific significance to study soil moisture,soil nutrients and grassland multiple ecosystem functions under reseeding treatment for the restoration of degraded grassland in arid and semi-arid areas.In this study,desert steppe in the southern margin of Mu Us Sandy Land was selected as the research area,and three reseeded treatments including monoculture Agropyron mongolicum(M),monoculture Lespedeza Potaninii(N),and their mixture Agropyron mongolicum×Lespedeza(MN)were set up;meanwhile an adjacent continuously grazed steppe selected as a Control(FM).Root morphological characteristics,soil structure,soil nutrients,microbial activity and above-ground vegetation characteristics were measured.The effects of reseeding restoration on soil soil properties and grassland multiple ecosystem functions were studied.The main research results are as follows:(1)All reseeded treatments significantly increased root volume and root biomass(P<0.05),and improved soil physico-chemical properties.In 0-40 cm soil depth,the soil water storage(except 30-40cm soil water storage),non-capillary porosity,capillary porosity and total porosity values of all supplementary seeding treatments were higher than those of FM.In addition,reseeding treatments(except N)also increased the contents of total nitrogen,total phosphorus,available phosphorus and nitrate nitrogen in 0-30 cm soil depth to varying degrees,and the value of M treatment showed a trend of higher than that of other supplementary sowing treatments.At the same time,the organic carbon and active organic carbon of light groups treated with M and MN in 0-20 cm soil layer were significantly higher than those treated with FM and N(P<0.05),but there was no significant difference between M and MN treatments(P>0.05).The active organic carbon in 20-40 cm of MN treatment was significantly higher than that in other treatments(P<0.05),but there was no significant difference in organic carbon in light group(P>0.05).Correlation analysis showed that soil properties(porosity,organic matter)and root morphological characteristics(root volume and root biomass)were significantly correlated with fine root volume(diameter≤2mm)(P<0.05 or 0.01).(2)Studies on the microbial community structure showed that the microbial species composition and a diversity of 0-20 cm and 20-40 cm soil were not very sensitive to the response of reseeding treatment,and only a few microorganisms such as proteobacteria and ascomycota had changes in abundance.Only treatment N significantly increased the fungal Chaol and Observed_species indices of 20-40 cm soil depth(P<0.05).However,the results of β diversity analysis showed that all the fungal communities of 0-40 cm were significantly separated from FM(P<0.05),but only M and MN were significantly separated from FM(P<0.05)in prokaryotic microbial communities.At the same time,compared with FM treatment,the three reseeding treatments significantly increased the activity of polyphenol oxidase in 20-40 cm soil(P<0.05),and also increased the activity of β-1,4-glucosidase,but there was no significant effect between the reseeding treatments(P>0.05).RDA model showed that fine roots significantly improved the community structure of fungi,promoted the nutrient cycling of fungi,and finally improved the soil nutrient content.(3)Reseeding significantly improved soil moisture and soil nutrient status,and then promoted the growth of above-ground vegetation,so the three reseeding measures significantly increased the versatility of above-ground ecosystems(P<0.05).However,compared with FM,M and MN treatments significantly improved the subsurface and total ecosystem versatility of desert grassland(P<0.05).Correlation results showed that above-ground biomass,coverage,organic carbon,light organic carbon,active organic carbon,total nitrogen,alkali-hydrolyzed nitrogen and total phosphorus were the main factors affecting ecosystem versatility,but fine root volume was the main driver of these factors.In conclusion,the reseeding of native species can improve soil water and nutrient content by increasing root input,and further improve the activity of microbial community,which in turn further promotes the cycling of soil carbon,nitrogen and other nutrients,and ultimately shows the increase of above-ground biomass of vegetation and the improvement of ecosystem versatility.Therefore,the restoration of native forage should be an important measure to maintain the multiple ecosystem functions of desert grassland ecosystem.In addition,in this study,fine root volume was a key factor that significantly affected soil water infiltration,microbial activity,soil nutrients and the versatility of grassland multiple ecosystem functions.Because of its well-developed fine roots,Agropyron mongolicum had the best effect in soil water improvement and soil nutrient input,and ultimately played the most significant role in enhancing the versatility of desert grassland multiple ecosystem functions.Therefore,the selection of herbage with high fine root volume for mixed sowing in arid and semi-arid areas may be more conducive to the restoration of degraded grassland and the improvement of multiple ecosystem functions. |
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