Abstract: Based on field investigation and laboratory analysis, the values of particulate soil nutrient content and nutrient content in bulk soil were examined using the method of timespace mutual substitution. The statistic analytical methods were used to analyze the relationship between the particulate soil nutrient content and nutrient content in bulk soil during the reversal of desertification in the multipleyear enclosed area to facilitate vegetation regeneration in Yanchi County, Ningxia Hui Autonomous Region. The results showed that, with the reduction of desertification degree, there was a gradual increase trend of the contents of SOC, N, P and K in each particle fraction and of SOC, N, P and K in bulk soil. Correlation analysis revealed that there was a significant positive correlation between the particulate soil nutrient contents in all the particle fractions and the soil nutrient contents in bulk soil. The enrichment of SOC, N, P and K contents in topsoil was a result jointly affected by both the fixation and storage of nutrients in bulk soil and the integration of nutrients in soil with different grains sizes during the reversal of desertification. Path analysis showed that the effects and importance of nutrients in soil with different grains sizes to nutrients in bulk soil were different, and the effects of unprotected particulate nutrients in very fine sand and moderatecoarse sand to nutrients in bulk soil was significant.

Key words: reversal of desertification, particulate soil nutrient, soil nutrient in bulk soil, correlation analysis, path analysis, Yanchi County, Ningxia