贺兰山西坡不同海拔梯度上土壤氮素矿化作用的研究

采用封顶埋管法对贺兰山西坡不同海拔梯度上土壤铵态氮(NH+4-N)和硝态氮(NO-3-N)以及Ｎ净矿化速率进行了研究。结果表明：①在海拔1 370～2 940 m的范围内,土壤铵态氮和硝态氮含量随海拔高度的降低而降低。②土壤N净矿化速率随海拔高度的降低呈现出明显的“V”字型变化规律,在海拔2 940 m 处最高（平均为0.272 mg·kg-1·d-1）,在海拔2 100 m处最低（平均为0.001 mg·kg-1·d-1）,之后又随海拔高度的降低而上升,在海拔1 370 m处达到0.136 mg·kg-１·d-１的水平。③回归分析显示,土壤矿化氮含量（NH+4-N +NO-3-N）与土壤含水量、全氮、有机质、群落中植物密度、地上生物量呈极显著正相关,与土壤容重、pH值呈极显著负相关。但土壤N净矿化速率与土壤含水量、全氮、有机质、容重、pH值之间却没有相关性。

Study of Soil Nitrogen Mineralization at Different Altitudes on Western Slopes of Helan Mountains,China

The Close-Top Incubation method was applied to study the variation of NH+4-N, NO-3-N and net N mineralization at different altitudes on the western slopes of the Helan mountains. The results are summarized as follows: ①The mean values of soil NH+4-N and NO-3-N decreased with elevation decreasing at the altitudes of between 1 370 m and 2 940 m. ②Net N mineralization rate decreased rapidly first and then increased with elevation decreasing, it took on “V” shapes from elevation 1 370 m to 2 940 m. Net N mineralization rate was the highest (0.272 mg·kg^-1·d^-1) at 2 940 m and the lowest(0.001 mg·kg^-1·d^-1) at 2 100 m, it increased with decreasing elevation below 2 100 m and reached 0.136 mg·kg^-1·d^-1 at 1 370 m. ③Regression analysis indicated that soil mineral nitrogen content had a closely positive relationship with soil water content, soil organic matter, soil total nitrogen, soil density, plant population density, plant aboveground biomass, and a closely negative relationship with soil density and soil pH; however, the net N mineralization rate had no correlation with soil water content, soil organic matter, soil total nitrogen, soil density, and soil pH.