[Soil particle composition, fractal dimension and their effects on soil properties following sand-binding revegetation within straw checkerboard in Tengger Desert, China].

This study aims to elucidate the effects of soil particle composition and fractal dimension on soil physical and chemical properties following sand-binding revegetation within straw checkerboard in south-eastern Tengger Desert. Three afforested plantations in the year of 2016 (i.e., 1 year), 2013 (i.e., 4 years) and 1987 (i.e., 30 years) were selected as study sites, with the adjacent mobile sand land as control (CK). We measured soil particle composition, soil fractal dimension, and the changes of soil physical and chemical properties. The relationship between soil particle composition, soil fractal dimension, and soil properties was analyzed. The results showed that contents of soil particle with the size of both 100-250 μm and 250-500 μm were greater than that of 50-100 μm, ranging from 42.5% to 80.1% and from 12.5% to 42.2% relative to that ranging from 0.2% to 20.8%. Contents of soil particle with the size of <2 μm and 2-50 μm were remarka-bly lower than that of 100-250 μm, 250-500 μm and 50-100 μm, ranging from 0 to 1.3% and from 0 to 22.7%, respectively. However, contents of soil particle at the size of 500-1000 μm was the lowest occupying <0.3% of soil particle composition. Soil particle with the size of <2 μm and 2-50 μm were found in the 30-year sites only. Soil particle distribution at the size of 50-100 μm, 100-250 μm, and 250-500 μm followed the order of 30 a>1 a>4 a＞CK, 4 a>1 a>CK>30 a, and CK>1 a>4 a> 30a, respectively. Soil particle with the size of 500-1000 μm occupied little of soil particle composition, with no significant difference between each site. The fractal dimension of soil particles ranged from 0.54 to 2.59. There was significantly greater soil fractal dimension in 30 a in comparison to 4 a, 1 a and CK, with the intermediate values in 4 a and 1 a, and the lowest values in CK. There was a significantly positive correlation of fractal dimension of soil particles with soil particle content of clay, silt, very fine sand, and a significantly negative correlation of fractal dimension of soil particles with soil particle content of medium sand. Fractal dimension of soil particles was positively correlated with soil electrical conductivity, organic carbon, total nitrogen, and carbon-nitrogen ratio, but with no correlation with soil pH and soil water content. Soil particle content at the size of <2 μm, 2-50 μm, and 50-100 μm had a significant positive correlation with soil electrical conductivity, organic carbon, total nitrogen, and carbon-nitrogen ratio, whereas soil particle content at the size of 250-500 μm had a negative correlation with the former four soil indices and soil water content. In addition, there was a significant negative correlation of soil particle content at the size of 500-1000 μm with soil water content. It was concluded that the sand-binding reve-getation within straw checkerboard in Tengger Desert could facilitate the fine soil particles by ameli-orating stressful soil conditions. Long-term succession of revegetation on mobile sand land could enhance soil clay and silt content as well as soil fractal dimension, thus be beneficial for the improvement of soil physical and chemical properties and desertification control.