不同功能型植物光合特性及其与叶氮含量、比叶重的关系

Photosynthetic characteristics and their relationships with leaf nitrogen content and leaf mass per area in different plant functional types

以秦岭南部的宁陕县和黄土高原地区的富县和神木为研究地点,研究不同气候带区乔木、灌木和草本植物的光合特性及其与叶片氮含量(Nmass)、比叶重(LMA)的作用关系。结果表明,宁陕、富县和神木3个地区之间的乔木、灌木和草本植物的光饱和速率(Pmax)、光合氮利用效率(PNUE)、PSⅡ电子传递量子效率(ФPSⅡ)、Nmass和LMA差异均达显著水平(p<0·05),神木地区乔木、灌木和草本植物的Pmax均显著高于宁陕和富县。3个地区的乔木、灌木和草本植物之间的Pmax、PNUE、ФPSⅡ、PSⅡ最大光能转换效率(Fv/Fm)、Nmass和LMA差异均达显著水平(p<0·05),草本植物的Pmax和PNUE明显高于灌木和乔木。由南向北分布的宁陕、富县和神木3个地区,随着气候干旱的加剧,乔木、灌木和草本植物的LMA均呈增加的趋势,且不同功能型植物的LMA的大小比较为乔木>灌木>草本植物。宁陕、富县和神木地区近60种植物(包括乔木、灌木和草本植物)的LMA与Nmass、PNUE与LMA均呈极显著的负相关(p<0·01),而Pmax与Nmass呈显著的正相关(p<0·05)。对光合参数之间的相关分析表明,Pmax与PNUE呈极显著的正相关(p<0·01),而Pmax与ФPSⅡ呈极显著的负相关(p<0·01)。

Quantifying correlations among leaf traits and trait differences between plant functional types （PFYs） not only gives insight into selective pressures that have shaped vegetation evolution, but also plays a crucial role in predicting vegetation productivity shift with climate and land use change. The photosynthetic characteristics, leaf nitrogen content （Nmass）, leaf mass per area （LMA）, as well as their relationships in trees, shrubs and grasses growing in three sites, Ningshan County located in Qinling Mountain, Fuxian County and Shenmu County both located in the Loess Plateau were studied. The results showed that there were significant differences （p 〈 0. 05 ） in the saturated photosynthetic rate （Pmax）, photosynthetic nitrogen use efficiency （PNUE）, quantum yield of PS Ⅱ electron transport （ФPSⅡ）, leaf nitrogen content （ Nmass ） and leaf mass per area （LMA） of three PFTs among Ningshan County, Fuxian County and Shenmu County. Trees, shrubs and grasses in Shenmu County had significantly higher mean values of Pmax than those in Ningshan County and Fuxian County. The Pmax, PNUE, ФPSⅡ, potential efficiency of primary conversion of light energy of PSⅡ （ Fv/Fm ）, Nmass and LMA differed significantly （p 〈 0.05 ） among trees, shrubs and grasses in three sites, and grasses had higher mean values of Pmax and PNUE than shrubs and trees did. The LMAs of trees, shrubs and grasses increased as climatic drought increased gradually from Ningshan County through Fuxian County to Shenmu County. The mean values of LMA for the three PFTs ranked in the order of trees 〉 shrubs 〉 grasses, and the LMA in trees was about twice times that in grasses. In＇60 plant species including trees, shrubs and grasses growing in Ningshan County, Fuxian County and Shenmu County, the LMA was significantly negatively correlated with the Nmass and PNUE （p 〈0.01 ）, while the Pmax was positively correlated with the Nmass （p 〈 0.05 ）. The correlation analysis among photosynthetic parameters showed that the Pmax was significantly positively correlated with the PNUE （p 〈0. 01 ）, but negatively correlated with the ФPSⅡ（P 〈0. 01 ）.