祁连山东段南麓不同海拔土壤有机质及全氮的分布状况

Soil Organic Matter and Total Nitrogen Changing with Altitudes on the Southern Foot of Eastern Qilian Mountains

在祁连山东段南麓设置实验样带,研究了植被生产力、土壤有机质和全氮等在不同海拔的分布状况及其影响因素.结果表明：海拔3 200 m开始到海拔4 300 m山顶,沿海拔升高年平均气温按0.51℃.100 m-1递减率下降.海拔3 200-3 800 m间植被生产力随海拔升高而降低.土壤有机质和全氮含量沿海拔从3 200 m开始下降至3 400 m后开始急剧上升,在海拔3 600 m处最高,而后又迅速下降;土壤有机质和全氮在土壤剖面中的垂直分布趋势一致,表层土壤有机质和全氮含量高,随深度加深而降低.土壤碳氮比介于6-14之间,相对较低,利于土壤腐殖质化和有机氮矿.土壤碳氮比沿海拔的升高先增加后减小,在土壤剖面中的分布随海拔的不同而有所差异.土壤有机质含量和全氮含量和气候因子、植被类型及放牧利用有关.

On the vertical zones on the southern foot of eastern Qilian Mountains,the distribution of vegetation primary production,soi1 organic matter and total nitrogen,as well their influencing factors are studied.It is found that the decreasing rate of the annual air temperature is 0.51℃·（100m）-1 and the productivity of vegetation decreases with increasing altitude.The contents of soi1 organic matter and total nitrogen decrease from 3 200 m to 3 400 m and then increase sharply,having a maximum at 3 600 m,followed by a rapid decrease upwards.The vertical changes of soi1 organic matter and total nitrogen have the similar trends.The contents of soi1 organic matter and total nitrogen are higher at the surface,and decrease with depth.The soil C/N ratio ranges from 6 to 14,which is lower than the appropriate C/N ratio of 25～30.The soil C/N ratio increases firstly and then decreases with altitude.And its distribution in the soi1 profile varies with elevation.Climate factors,vegetation types and grazing types control the contents of soi1 organic matter and total nitrogen.