祁连山青海云杉叶片氮、磷含量随海拔变化特征

于2005年9月在祁连山北坡沿海拔梯度测定了青海云杉(Picea crassifolia)叶片氮、磷含量.结果表明,青海云杉叶氮、磷平均含量分别为9.75和0.97 mg·g-1.在种间水平上,青海云杉叶片氮、磷含量明显低于全球松科其它针叶树种;在种内水平上,随着海拔的增加,青海云杉叶片氮含量表现出降低的趋势,叶片磷含量变化趋势不明显.叶片氮含量与年均气温呈显著正相关关系(r=0.616**),与土壤水分呈显著负相关关系(r=-0.640**),与土壤有机质、全氮均呈显著负相关关系(r=-0.591**,r=-0.564**);叶片磷含量与年均温、土壤水分之间的关系不显著;叶片氮、磷之间的比率为10.2.表明温度和水分对青海云杉叶片氮、磷含量的影响主要是通过影响土壤生物化学过程(如养分有效性、根系对养分的吸收等)来实现的,青海云杉生长更多的受到氮素限制.

Variations in Leaf N, P of Picea crassifolia along the Altitude Gradient in Qilian Mountains

Leaf nitrogen (N) and phosphorus (P) of Picea crassifolia were investigated along altitude gradient in northern slope of Qilian Mountains in September,2005. The results indicated that the mean N,P in and P of P. crassifolia were lower than those of most other coniferous tree species in pine family globally.At intraspecific level,leaf N decreased with increase of altitude,while leaf P showed no clear pattern along altitude. Leaf N was significantly positively related to mean annual air temperature(r=0. 616**), but negatively related to soil water content(r= -0.640**). Moreover,leaf N was negatively related to soil organic matter (SOM) and total nitrogen (TN)(r=-0.591** ,r=-0.564**). The relations of leaf P to temperature,soil water content, SOM and TN were not significant. Additionally, ratio of leaf N : p was 10. 2.Hence,the influences of temperature and water availability on leaf N,P of P. crassifolia would mainly lie in soil biogeochemical process (e. g. soil nutrient availability,root nutrients uptake) ,and P. crassifolia was more limited by nitrogen,rather than phosphorus.