Spatially heterogeneous characteristics of surface soil particles around nebkhas in the Gobi Desert

Abstract

Aims We studied single desert shrubs and their role in sand accumulation to provide references for monitoring and evaluating soil wind erosion and for scientifically establishing controlling measures. This research is important for strengthening sand fixation effects of vegetation. Methods We obtained percentage composition of soil particles in wind erosion surfaces around single shrubs of Nitraria tangutorum and Ammopiptanthus mongolicus in the Gobi Desert north of Jilantai salt lake with digital image processing technology. We analyzed their horizontal spatial heterogeneities by classic descriptive statistics and geostatistical methods. Important findings Enrichment of soil fine particles appeared on the base of nebkhas and in the downwind direction. The percentage of soil particles (0.42 mm) decreased from the center of shrubs to the sample plot. The maximum value of soil particles enrichment was on the windward side around N. tangutorum and on the leeward side of A. mongolicus. In the Gobi Desert where sand material is limited, the effect of wind prevention and sand fixation was concentrated around N. tangutorum, although the spatial scale affected was smaller than with A. mongolicus. This explained that the degree of coarse grains in the N. tangutorum sample plot was higher than that of A. mongolicus. The spatial heterogeneity scales of soil particles (0.84 mm, 0.42–0.84 mm and 0.42 mm) in wind erosion surface around N. tangutorum and A. mongolicus were 17.80, 66.63 and 8.41 m and 9.82, 15.33 and 14.91 m, respectively, all of which were beyond the shrub canopy cover. The proportion (C/(C 0 + C)) of structured elements was 63.40% to 99.96%, which indicated that wind-drift sand characteristic around nebkhas was the mostimportant factor in the spatial heterogeneity of soil particles of corresponding scale. The spatial heterogeneity scale of highly erodible soil particles was greater than the average space of nebkhas (8.77 m, which included the semidiameter of nebkhas). The prevention of soil wind erosion by the relation between nebkhas and species is beneficial for stabilization and development of vegetation in this area.