[Impact of short-term grazing disturbance on nitrogen accumulation of biological soil crusts in the hilly Loess Plateau region, China]. / çŸ­æœŸæ”¾ç‰§å¹²æ‰°å¯¹é»„åœŸä¸˜é™µåŒºç”Ÿç‰©ç»“çš®åœŸå£¤æ°®ç´ ç´¯ç§¯çš„å½±å“.

The variations of total nitrogen, available nitrogen and microbial biomass nitrogen caused by simulated grazing disturbance were investigated in the sixth and twelfth months by using field survey combined with laboratory analysis in order to reveal the sensitivity of nitrogen content in biocrustal soils to disturbance in the hilly Loess Plateau region. The results showed that nitrogen contents in biocrustal soil were sensitive to disturbance. Total nitrogen and available nitrogen in the biocrustal layers were decreased by 0.17-0.39 g·kg-1 and 1.78-5.65 mg·kg-1 during the first half-year compared to the undisturbed treatment, and they were found respectively decreased by 0.13-0.40 g·kg-1 and 11.45-32.68 mg·kg-1 one year later since disturbance. The content of microbial biomass nitrogen in the biocrustal layer was reduced by 69.99-330.97 mg·kg-1, whereas the content was increased by 25.51-352.17 mg·kg-1 in soil of 0-2 cm layer. The induction of nitrogen accumulation depended on the intensity of disturbance. Slight variation was observed in the nitrogen accumulation in biocrustal layer under 20% and 30% disturbance, while significant reduction was found in the 40% and 50% disturbance. Significant reduction was detected only in nitrogen accumulation in the biocrustal layers, whereas no significant influence was found in the top 5 cm soil layer.