Changes in soil properties during reversal of desertification in agro-pastoral transition zone of Northern China

Based on the field surveys and laboratory analysis, soil physical, chemical and biological properties were studied at different degrees of the reversal of desertification in the agro-pastoral transition zone of northern China. The resultsobtained show that with the consequence of mobile sand land →semimobile sand land →semi-fixed sand land →fixed sand land, the dominant soil particle size changed from coarse sand to a combination of fine sand and silt + clay, and corresponding levels of each soil nutrient increased. The content of coarse sand (>0.25 mm) was significantly and negatively correlated with soil nutrient contents, whereas nutrient contents were significantly and positively correlated with the contents of fine sand (0.25 to 0.02 mm) and silt + clay (<0.02 mm). The increasingly fine soil texture and the nutrient enrichment both facilitated rehabilitation of desertified land. The path analysis showed that soil organic matter was the main factor that affected soil enzymes activities directly while total potassium (P) was less important. Principal-components analysis (PCA) revealed that the soil quality tend to increase during the reversal process and that biological factor were more significant than nutrient factors and particle size. Fine sand was the most important particle factors.