广西猫儿山不同海拔常绿树种和落叶树种光合速率与氮的关系

Photosynthesis-nitrogen relationship in evergreen and deciduous tree species at different altitudes on Mao′er Mountain,Guangxi

分析广西猫儿山不同海拔常绿和落叶树种的光合作用-氮关系,探讨光合氮利用效率(PNUE)是否受到叶片习性和海拔的影响。落叶树种的PNUE都显著高于常绿树种,这与前者有较低的比叶重(LMA)和较高的单位叶重光合速率(Amass)、氮含量和气孔导度(gs)有密切关系。高海拔树种的PNUE显著低于中低海拔树种的PNUE,这与前者较高的LMA和较低的Amass和gs相关。PNUE和相关的叶片特征的主成分分析表明常绿-落叶树种和低海拔-中海拔-高海拔树种的分布是一个自然过渡的过程。此外,PNUE与土壤碳:氮比没有显著相关性,但与年均温正相关,这表明温度气候是调节PNUE沿海拔变化的主要环境因素。因此,这种叶片习性和温度气候调节的PNUE变化可能是调节猫儿山常绿树种沿海拔形成双峰分布的一种机制。

The present study analyzed the photosynthesis-nitrogen relationship in evergreen and deciduous tree species at different altitudes on Mao′er Mountain,Guangxi,and explored whether photosynthetic nitrogen use efficiency（PNUE） was affected by leaf habit and altitude.Deciduous tree species had significanlty higher PNUE than evegreen tree species because of lower leaf mass per area（LMA） and higher photosynthetic rate per mass（Amass）,nitrogen content and stomatal conductance（gs） in the former.Tree species at high altitude had significantly lower PNUE than those at middle and low altitudes due to higher LMA and lower Amass and gs in the former.Principal component analysis for PNUE and its related leaf traits suggested that the tree species distribution of evergreen-deciduous and low-middle-high altitude were in the process of natural transition.In addition,PNUE was not related to soil carbon： nitrogen ratio,but significantly positive related to mean annual temperature,suggesting that temperature climate was the main environmental factor that regulated the altitudianl changes in PNUE.Therefore,this differential PNUE that was affected by leaf habit and temperature climate was a mechanism for the bimodal distribution of evergreen tree species along the altitudes on Mao′er Montain.