The surface sediment grain size, available nutrient distribution and sand environment in the Eastern Sand Area of China

State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing, China

The main objective of the research was to determine the relationship between physicochemical properties of surface sediments and regional and local aeolian environment in the eastern desert area of China. We collected sediment samples of sand dunes with differentmobility at the five desertsin theses area, namely Hobq desert,Mu Us sandy land, Otindag sandy land, Horqin sandyland and the Hulunbuir sandy land. Samplegrain size composition and thecontent of organic matter and available nutrientswere tested. Analysis of spatial characteristics of mean grain size, sorting coefficient, content of organic matter and available nutrients, and thecorrelation between these parameters and vegetation coverage, regional wind force and dune activityindex show that surface sediments for all five desertsare mainly composed of fine sand and medium sand and medium sorted. The mean grain sizes vary from 2.14 to 2.58Φ. Contents of organic matter and available nutrients are generally very low.From west to east, in the order of Hobq desert, Mu Us sandy land, Otindag sandy land, Horqin sandy land and Hulunbuir sandy land, sediments tend to be coarser, sorting become worse,contents of organic matter and available nutrients increase gradually. The good sorting (average standard deviation is equal to 0.57Φ) and low contents oforganic matter andnutrientsin Hobq desert closely associated withaeolian activities that was characterized by frequently alternated occurrence of wind erosion, particle transportation anddeposition. Such an aeolian environment is favorable for particle sorting but unfavorable for accumulation of soil nutrients. InHulunbuir sandy land, precipitation is relatively sufficient andthe vegetation coverage and the background conditionsof soil nutrients are better than those of the other deserts. However,the strongest regional wind forceresulted ina wind erosion process dominatedaeolian environment.Therefore,physicochemical propertiesof the surface sedimentswere mainly determined by the regional background with high contentof soil nutrients and poor sorting (averagestandard deviation of grain size is equal to 1.03Φ). In Mu Us, Otindag and Horqin sandy lands, the interlace distribution of wind erosion dominated areaswith sparse vegetation and the aeolian deposition dominated areaswith good vegetation cover produceda more complex regional aeolian environment than the Hobq and Hulunbuir, which weakened wind sortingprocess (standard deviation of grain size ranges from 0.64Φ to 0.89Φ) and reduced the loss of soil nutrients.

Ineach desert,mean grain size, sorting coefficient, organic matter content and available potassium content are statisticallycorrelated tolocal vegetation coverage to different degrees, whereasorganic matter content and available potassium content are well correlated to particle sorting coefficient.Available nitrogen and phosphoruscontent do not exhibit correlations to local vegetation coverage and particle sorting coefficient. This suggests that the grain size, organic matter and available potassiumcontent of surface sedimentsare sensitive to the change of aeolian environment, while available nitrogen and phosphorus cannot index the aeolian environment.

Key words: Eastern desert area of China; surface sediments; grain size; soil nutrient; aeolian environment