Spatial Heterogeneity Of Soil Moisture, Organic Carbon And Available Nitrogen In The South Gurbantunggut Desert

Soil moisture and soil nutrients were desert vegetation development of key factors, which were present spatial variability in difference scales. In July 2014, spatial heterogeneity of soil moisure, soil organic carbon (SOC) and available nitrogen (AN) at the individual scale, community scale and interdune lands scale was measured in the South Gurbantunggut Desert in 0-100 cm depth. Individual scale with 20 cm intervals was divided into five layers; At community scale and interdune lands scale, We sampled soil at 0-30 cm,30-60 cm and 60-100 cm depth. Through field sampling combined with laboratory analysis at different scales, analysis the spatial heterogeneity of soil moisture, organic carbon and available nitrogen in the south Gurbantunggut Desert. The results are as follows:From the surface to the deep, the mean soil moisture were 0.51%,1.17%,1.30%,1.38%, 1.51%, it shows the mean soil moisture increased significantly with soil depth increasing from 0 to 100 cm under the same scale. However, the coefficient variation (CV) of top soil (20.71%) was greater than other soil depths(2.51～5.86%), which indicating that under different terrain and vegetation, top soil moisture compared to other soil layers has a greater heterogeneity by evaporation effects. From the surface to the deep, the mean SOC were 2.95 g/kg,2.65 g/kg,2.44 g /kg,2.27 g/kg,2.11 g/kg; and the mean AN were 29.58 mg/kg、22.85 mg/kg、19.21 mg/kg、15.43 mg/kg、14.15 mg/kg, it shows that SOC and AN decreased significantly with soil depth increasing. The CV values of SOC and AN less than 10% at all scales, which indicated a weak spatial variability in the study areas.Individual scale, at the horizontal directions, with the outward from tree base increased, the soil moisture at crest increased 0.707% to 0.977%, showed an increasing trend; while the soil moisture decreased 1.225%,1.320% down to 1.055%,1.824% at midslope and interdune slope, showed a decreasing trend. with the outward from tree base increased, the SOC followed by 2.53g/kg、3.18 g/kg、3.49 g/kg down to 1.71 g/kg、1.73 g/kg、2.09 g/kg, the AN followed by 21.59 mg/kg、27.42 mg/kg、35.94 mg/kg decreased to 13.52 mg/kg.15.63 mg/kg.17.21 mg/kg, showed a decreasing trend. It indicates that the patterns of spatial distribution of soil moisture, organic carbon and available nitrogen around H.ammodendron base were different in the horizontal directions. At the vertical directions, At the vertical directions, from top to deep soil 5 layers, the soil moisture of crest followed by 0.367%、0.798%、0.932%、1.085%、1.192%; the soil moisure of midslope followed by 0.512%、1.075%、1.208%、1.295%、1.400%; the soil moisure of interdune followed by 0.658%.1.632%、1.763%、1.768%、1.938%, All three had an increasing trend. from top to deep soil 5 layers, the SOC of crest followed by 2.56 g/kg、2.18 g/kg、2.00 g/kg、1.98 g/kg、1.88 g/kg; the SOC of midslope followed by 2.80g/kg、2.69 g/kg、2.44 g/kg、2.38 g/kg、2.18 g/kg; the SOC of interdune followed by 3.52 g/kg、3.10 g/kg、2.91 g/kg、2.47 g/kg.2.27 g/kg, All three had a decreasing trend. from top to deep soil 5 layers, the AN of crest followed by 23.78mg/kg、17.10 mg/kg、16.69 mg/kg、12.01 mg/kg、11.17 mg/kg; the AN of midslope followed by 28.72mg/kg、 22.78 mg/kg、18.27 mg/kg、15.89 mg/kg、14.17 mg/kg; the AN of interdune followed by 36.25mg/kg、28.69 mg/kg、22.67 mg/kg、18.40 mg/kg、17.11 mg/kg, All three had a decreasing trend.On community scale. At the vertical directions, with soil depth increasing, the mean soil moisture from 0.62% increased to 1.54%, showed an increasing trend; The mean SOC from 3.15 g/kg down to 2.24 g/kg, and the mean AN from 37.49 mg/kg decreased to 15.98 mg/kg, showed a decreasing trend. At the horizontal directions, from shrub canopies to interspace, Soil moisture from the 0.67%,1.32%,1.61% down to 0.60%,1.21%,1.51%; the SOC from the 3.57 g/kg,2.90 g/kg、2.36 g/kg down to 2.99 g/kg、2.59 g/kg、2.18 g/kg; the AN from 43.19 mg/kg、28.25 mg/kg、 17.89 mg/kg decreased to 35.23 mg/kg、22.79 mg/kg、15.22 mg/kg, showed a decreasing trend. The result indicated that soil moisture, SOC and AN was had stronger effect by H.ammodendron shrubs, which higher in canopied than interspace.At the interdune land scale, correlation analysis showed a significant negative correlation between soil moisture and elevation (P<0.01), eventually forming the results that soil moisure highest(2.15%) for interdune, lowest (0.16%)for crest, medium for mid-slope. Soil moisture, SOC and AN reached significant positive correlation between the three (P<0.01), show the distribution pattern of soil moisture, SOC and AN was consistent. Which indicated terrain factor is the main factors which affect the spatial heterogeneity of soil moisture, SOC and AN.