[Spatial distribution patterns of dry sand layer on windward slope of dunes in Horqin Sand Land]

An observation was conducted on the thickness of dry sand layer on the windward slope of mobile and fixed dunes in west Horqin Sand Land, with the spatial distribution of the dry sand layer analyzed. Most of the dry sand layer had a thickness of 5-15 cm, and 92.0% and 98.6% of the mobile and fixed dunes had the dry sand layer with this thickness, respectively. Sand-fixing plants affected the thickness and the spatial distribution of the dry sand layer. There was an obvious spatial difference in the thickness of the dry sand layer on mobile dunes, being much thicker in the upper west areas while much thinner in the lower east areas. The thickness of the dry sand layer varied from 0 to 40 cm, with an average of 9.58 +/- 3.95 cm, and the CV was 41%. The variogram of the spatial distribution of dry sand layer on mobile dunes was expressed as spherical model, with a moderate spatial correlation. In contrast, the thickness of dry sand layer on fixed dunes showed obvious homogeneity, and had less spatial difference. The thickness of the dry sand layer ranged from 0 to 20 cm, with an average of 10.91 +/- 1.70 cm, and the CV was only 16%.