Carbon Sequestration Effect Of Different Shrublands Under Brackish Water Irrigation In Hyper-Arid Desert Areas

The natural environment in the Taklamakan Desert is extremely harsh with extreme drought climate and severe evaporation,which lead to extremely scarce natural vegetation there.The plant species of Taklamakan Desert Highway Shelterbelt(TDHS)are the mainly excellent wind and sand setting shrubs with strong resistance to adversity,and the forest belt is configured by inter-row mixing and drip irrigation by extracting regional underground brackish water.In this study,three shrub stands Tamarix chinensis(CL),Calligonum mongolicum(SG)and Haloxylon ammodendron(SS)of different ages(18,20,22 and 24years)in desert road protection forest were selected as sampling points,and the drifting sands were used as control(CK),and after sampling,testing and data analysis,it has been investigated that the spatial distribution characteristics of soil carbon in different shrublands of the desert road protection forest and the influence of physicochemical factors on it,and further estimated its carbon sequestration potential,to make reasonable suggestions for the construction and management of the protection forest.The main conclusions include:(1)The soil organic carbon(SOC)content of the three shrublands was significantly increased.SOC content of the protection forest showed a trend of increasing and then decreasing,and then stabilized at about 100 cm depth.The SOC content in SG stands was found to be highest and the lowest under CL stands,however,the SOC content in all three shrublands was higher than that in CK,[SG(1.74 g/kg)>SS(1.52 g/kg)>CL(1.27 g/kg)>CK(0.94 g/kg)].The SOC content in SS and SG stands increased with the increase in age of the stand,while the opposite was true for CL.Soil carbon density(SOCD)at 1 m depth showed that SG has maximum value as compared to control[SG(2.975 kg C/m~2)>SS(2.50 kg C/m~2)>CL(2.05 kg C/m~2)>CK(1.41 kg C/m~2)],and SOCD was found to be more under SG[SG(4.39 kg C/m~2)>SS(3.91 kg C/m~2)>CL(3.40 kg C/m~2)>CK(2.91 kg C/m~2)]at 2 m depth.(2)Soil inorganic carbon(SIC)content was significantly increased in the three shrublands.18 and 22 years stands showed an increasing trend in SIC at the surface layer with increasing soil depth and then decreasing with increasing depth,while 20and 24years stands showed a decreasing trend in SIC.However,the 18,22,and 24years stands showed an increasing trend in SIC content with SS(12.26 g/kg)>SG(11.97g/kg)>CL(11.88 g/kg)>CK(10.53 g/kg),while the SIC content of 20years stands showed that SS(10.58 g/kg)>CK(10.53 g/kg)>SG(10.42 g/kg)>CL(7.07 g/kg).Soil inorganic carbon density(SICD)of the three shrub stands exhibited SS(36.63 kg C/m~2)>CL(35.99 kg C/m~2)>SG(34.65 kg C/m~2)>CK(29.37 kg C/m~2)at 2 m depth.(3)The average biomass size of the three shrubs showed that SG(27.62 kg/plant)>SS(15.31 kg/plant)>CL(7.00 kg/plant),and the biomass of all three shrubs species increased with the age,and the increase became slower with time and become neutral.(4)The average organic carbon density(SOCD)of the Taklamakan Desert Highway Protection Forest was 3.932 kg C/m~2 and the average inorganic carbon density(SICD)was 33.45 kg C/m~2.At 200 cm depth range,the SOC and SIC storage was 0.134and 1.137 Tg,respectively.The potential of SIC sequestration was 2.003 Tg(87.58%),and the total carbon sequestration potential was 2.287 Tg at 2 m depth.In conclusion,the carbon sequestration benefits and sequestration potential of the Taklamakan Desert protective forest construction are huge,and the ecological carbon sequestration potential of SG is the largest among the three shrubs,so it is recommended that SG should be selected as the main afforestation species during the protective forest construction in the Taklamakan Desert region.