Long-Term Effects Of Different Vegetation Restoration Models On Distribution Of Soil Moisture-Carbon And Carbon Sequestration In The MU US Sandy Land

Land degradation is one of the main reasons caused the degradation of ecological environment.Vegetation construction measures can effectively improve the soil quality of degraded sandy land.The changes of soil water and carbon under the vegetation restoration measures in arid and semi-arid degraded desert regions and the influencing factors are helpful to further reveal the characteristics of desert soil evolution process,which is of great significance to regional ecological environment construction and sustainable management.In this paper,the arbor forest,shrub forest,grassland and shifting sand land in the artificial vegetation restoration area on the southeastern margin of the Mu Us Sandy Land were selected as the study plots.Based on the field investigation and indoor analysis,the distribution characteristics and influencing factors of soil moisture and soil carbon in the 0-500 cm profiles were studied.The main findings are as follows:(1)Vegetation type and recovery period have significant effects on soil moisture,and root distribution has a significant impact on it,and soil texture has a certain impact on it.The total water storage capacity of arbors and shrubs were 16.62 mm and 26.36 mm higher than that of shifting sandy land,but the total water storage of grassland was 52.65 mm less than that of shifting sandy land.The total water storage of arbor forest planted for 56 years,arbor forest and shrub land restored for 21 years was 99.84 mm,47.44 mm and 103.42 mm higher than that of shifting sandy land.In the 21-year arbor forest and 36-year shrub land,the root length density was significantly negatively correlated with soil water content(P<0.05).There was a significant negative correlation between root length density and soil water content in grassland and shrub land restored for 56 years and shrub land restored for 21 years(P<0.01).There was a significant negative correlation between soil water content and silt and sand particle content(P<0.05)in grassland.There was no significant correlation between soil moisture and soil texture in other plots.(2)Soil inorganic carbon(SIC)is the main form of soil carbon pool in Mu Us Sandy land.The soil inorganic carbon density(SICD)in the study area is 7.51 times that of soil organic carbon density(SOCD).Soil organic carbon(SOC)and SIC contents increase with the restoration periods,and the accumulation effect of SOC in arbor forest and SIC in shrub land was the best.Soil water content,pH and sand content were negatively correlated with SOC.EC,particle silt and clay were positively correlated with SOC,and the above factors were not significantly correlated with SIC.(3)Vegetation recovery years have an important impact on soil particle composition and carbon content in different grain sizes.With the increase of planting years,soil particles showed a trend of refinement,and the content of fine particles in the surface layer(0-5 cm)was higher than that in the beneath layers(5-30 cm).The contents of SOC and SIC increased significantly after afforestation,and the highest value was 4.90 times and 4.32 times of the shifting sandy land.The effect of planting years on SOC content and soil organic carbon density(SOCD)was greater than that of SIC and SICD.SOC and SIC content of each particle size increased the most in the 56-year plot,and the increase was the largest among the fine sand components.There was a significant linear correlation between the content of organic carbon in agglomerates and silt-clay particles and soil total organic carbon(P<0.01).The contribution rate of SOC in coarse sand particles and silt-clay particles to total organic carbon,and the contribution rate of SIC in silt-clay particles to total inorganic carbon were significant(P<0.05).(4)Vegetation restoration types have an important impact on soil particle composition and carbon content in different grain sizes.Different types of vegetation restoration would reduce the content of coarse grains(fine sand and coarse sand).Among them,the fine sand content of grassland decreased the most,and the coarse sand content of shrub-like land decreased the most.The content of aggregates and silt and clay was increased.Among them,grassland aggregates increased the most,and arbor-like ground powders increased the most.The content of SOC and SIC significantly increased after vegetation restoration,and the highest value in arbor forest was 3.96 times and 2.08 times higher than that of shifting sandy land.The effect of vegetation restoration on soil organic carbon density(SOCD)was more obvious than soil inorganic carbon density(SICD).The arbor is beneficial for SOC fixation in coarse sand and fine sand,and shrub was more beneficial for SOC fixation of in the silt and clay and aggregates.SOC content of each grain particle increased most obviously in fine sand particles,and SIC increased most obviously in silt–clay particles.The contribution rate of SOC in silt-clay particles to total organic carbon was significant.In summary,from the perspective of improving soil moisture status and increasing soil carbon sequestration,vegetation restoration in Mu Us Sandy land should be dominated by arbors and shrubs.The above conclusions can provide a theoretical basis for vegetation restoration and construction in degraded sandy land in semi-arid areas.