| The fragile ecosystem environment has been subjected to severe erosion and land degradation on the Loess Plateau.Small watershed is the basic unit of ecological ecological restoration and vegetation rehabilitation.Artificial vegetation restoration is the fundamental management to construct ecological environment on the Loess Plateau.However,the spatial variability of soil aggregate stability in small watershed and its driving factors have been studied fully.This thesis focusede on typical samples in the Huochawan watershed,Ningxia autonomous region,which is mainly planted shrubs such as Caragana korshinskii.Based on field investigation and laboratory analysis,using geo-statistics and GIS technolges,the spatial variabilitis and relationships among soil organic carbon,soil aggregate stability and glomalin-related soil protein(GRSP)were analysized.Additionally,combined with the soil physical and chemical factors and geographical environment factor analysis,the main driving factors were identifed.The results were expected to provide a scientific basis for the evaluation of regional eco-environmental and management on the Loess Plateau.The main results were shown as following:(1)In all cases,the highest proportions were found in smaller macro-aggregates(2-0.053 mm),and the lowest were in small aggregates(< 0.053 mm).The values of mean weight diameter(MWD)arranged from 0.50 to 3.12 mm,and its variation degree were12.91% to 57.80%,which was a medium degree of variation.The spatial heterogeneity ratio of MWD was 0.04%-15.65%,indicating that there was a strong spatial autocorrelation and dominant structural variation.The results of Kriging interpolation showed that the highest values of MWD were found in C.korshinskii,while that of cultivated land and natural grassland were lower.(2)The distribution of soil organic carbon(SOC)content,SOC storage(SOCS)and aggregate-associated SOC content differed across different land use types(p < 0.05),which were as follows: forest land > shrub land > farmland > grassland.The former were intermediate variability with the coefficient of variation(CV)of 11.95%-22.18%,while the latter was weak variation with 3.63%-7.54%.The spatial heterogeneity ratio of the three indexes was 0.10%-20.19%,which showed that there were the strong spatial autocorrelation and structural variation.Slope position and land preparation had been generated significant effects on SOC,SOCS and aggregate-associated SOC in the whole small watershed(p < 0.05).The amount of SOC sequestration was increased significantly by planting C.korshinskii in the small watershed(p < 0.05).(3)The GRSP within bulk soil and aggregate were significant differences among different land use types,especially for shrubland planting C.korshinskii was higher than agricultural land,and the lowest was in grassland.In addition,the CV of GRSP was intermediate variability with the spatial heterogeneity ratio of < 25%,indicating that there was strong spatial autocorrelation and structural spatial variation.The autocorrelation of spatial distribution of easily-extracted GRSP(EE-GRSP)was stronger than that of the total-extracted GRSP(T-GRSP),especially for diameter with 0.25-0.053 mm.(4)Land uses and land preparation types had important influences on the stability of aggregates,SOC and GRSP in the small watershed.The land use types and land preparation types mainly affected soil structure at the surface depth(0-10 cm)and deeper depth(10-20cm),respectively.SOC were significantly correlated with MWD and GRSP(p < 0.05).In overall,the positive carbon sequestration and accumulation of GRSP by plantation of C.korshinskii can further improve the aggregate stability.Meanwhile,the spatial distribution of soil aggregate stability and SOC and GRSP,and their variability were also significantly affected by land use and land preparation type in the small watershed.Therefore,it will be necessary to combine land preparation and vegetation type in the regional vegetation restoration. |
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