Scales Affect the Soil Spatial Heterogeneity of Haloxylon Ammodendron (C. A. Mey.) in a Sandy Desert

Haloxylon Ammodendron Bge (C.A. Mey.) is a dominant shrub species in the Gurbantonggut Desert, which is the largest fixed and semi-fixed desert in China, and plays an important role in preventing wind erosion and combating desertification, typically by developing fertile islands in desert ecosystems; however, such islands often depend on the scales.  

To understand the mechanisms underlying the development of these fertile islands and the spatial distribution of soil resources, LI Congjuan et al. measured the soil chemical properties of sampling from both the individual and population scales, and then used geostatistical techniques to analyze the spatial variability of the soil properties at the two scales and used Semivariogram model to describe the spatial variation of the soil properties for H. ammodendron. 

The results showed that the soil electrical conductivity (EC), soil organic carbon (SOC), and total nitrogen (TN) were significantly higher at the individual scale than the population scale. Moreover, the coefficients of variation (CV%) of the soil parameters at the individual scale were greater than they were at the population scale, with all except for pH (CV = 4.35% for individual scale and CV = 2.87% for population scale) presenting a moderate degree of variability (10%＜CV＜100%). The geostatistical analysis revealed a strong spatial dependence [C₀/(C₀+C)＜25%] within the distance of ranges for the tested parameters at both scales. The kriging interpolation results presented significant accumulation of soil SOC and TN around the shrub center and formed a significant ‘‘fertile island’’ at the individual scale, whereas the soil EC was much lower at the shrub center. At the population scale, patch fragments of the soil chemical properties were observed; however, not all individuals presented significant fertile islands or salt islands, and the soil EC presented a similar distribution as SOC and TN. 

The above differences suggested that different mechanisms controlled the spatial distribution of soil minerals at the two scales and that the spatial heterogeneities are scale-dependent in a desert ecosystem. The study was published in Environmental Earth Sciences in May 2014.