Abstract:

In this paper, the effects of different land-use types on soil particle size distribution in the process of oasisization were detected based on a survey conducted in orchard, cotton farmland and Caligonum mongolicum plantation and naturally regenerated Alhagi sparsifolia vegetation in the rim of Cele oasis located in south rim of Tarim Basin. Soil samples were collected in the depth of 0-20, 20-40, 40-60 cm respectively, and the characteristics of soil particle size distribution in the different vegetation soil were analyzed using the fractal theory and canonical correspondence analysis. The correlation between particle size distribution and other eight soil properties, such as soil organic matter etc., was also analyzed. Then the rational land-use types in oasis rim were further discussed and identified. Results showed that the volume content of soil fine fractions (lower than 50.59 μm) had significantly positive correlation with the fractal dimension value of particle size distribution, also had significantly positive correlation with the content of soil organic matter and total nitrogen, and had significantly negative correlation with bulk density. C. mongolicum forest had the lowest variation in fractal dimension values at each soil depth, and other land-use types had no significant difference in the values but the orchard was relatively higher. The natural state land-use type covered by A. sparsifolia had a trend that fractal dimension value gradually increased with increasing soil depth, and its ability to hold soil nutrients was gradually stronger than other land-use types. These results indicated that development of orchard or cotton farmland was beneficial to maintaining or improving soil particle size distribution and other soil properties with a precondition that the water supply would be ensured. To the contrast, the natural vegetation should be maintained, and replacement of the natural vegetation by C. mongolicum forests could exacerbated the soil degeneration.

Key words: soil particle size distribution, fractal dimention, canonical correspondence analysis, oasis, Tarim Basin