沙坡头地区藓类结皮土壤净氮矿化作用对水热因子的响应

采用室内控制温度(-10、5、15、25、35和40 ℃)和湿度(29%、58%、85%和170%田间持水量，FWC)培养原状土柱的方法，研究腾格里沙漠东南缘天然植被区藓类结皮土壤氮矿化特征及其对水热因子的响应.结果表明： 低温(<15 ℃)培养时，土壤氮素转化以微生物固持作用为主，>25 ℃后土壤氮素转化速率显著增加.藓类结皮土壤氮素转化速率及其对温度的敏感性均高于无结皮土壤，且在85%FWC时敏感性最高，表明藓类结皮的存在有利于土壤氮素的转化.随着土壤湿度的增加，土壤氮素转化速率呈先增加后减小的趋势，85%FWC时最大.藓类结皮土壤净氮矿化速率在高温(25～40 ℃)和中等水分条件下(58%FWC和85%FWC)最大，呈现明显的温湿度交互作用.藓类结皮的繁衍和拓殖能够提高土壤的供氮能力，促进氮素循环，有助于土壤生态系统的修复.

Responses of net soil nitrogen mineralization rate in moss-covered soil to hydrothermic factors in Shapotou regions,northern China.

Undisturbed soil cores were incubated in laboratory at different temperatures (-10, 5, 15, 25, 35 and 40 ℃) and moistures (29%, 58%, 85% and 170% of field water content, FWC) to analyze the effect of moss crusts, which were sampled from the natural vegetation area of Shapotou, on soil nitrogen transformation and their responses to hydrothermic factors. Results showed that immobilization was the dominant form of nitrogen transformation at the lower temperatures (<15 ℃), and when the temperature surpassed 25 ℃, the nitrogen transformation rate signi ficantly increased. The nitrogen transformation rate in the moss-covered soil was more sensitive to temperature variation than in the bare soil, and the highest temperature sensitivity was at 85%FWC. It indicated that the existence and succession of moss crusts facilitated nitrogen transformation. In addition, the nitrogen transformation rates of two microhabitats increased initially and then declined with the increasing moisture, and the maximum nitrogen transformation rate was observed at 85% FWC. Significant interactive effects were found between temperature and moisture in the moss-covered soil. While, the greater enhancement in nitrogen transformation rate appeared at higher temperatures (25-40 ℃) and moderate moisture levels (58%FWC and 85%FWC). It was concluded that the existence and succession of moss crusts would increase the ability of soil nitrogen supply, promote nitrogen cycling and even contribute to the restoration of soil ecosystem.