杨树光合特性及叶片营养分布的空间异质性

Spatial Heterogeneity of Photosynthesis Characteristics and Leaf Nutrition Distribution in Poplar

以I-107欧美杨为研究对象,观测了不同冠层净光合速率的日变化、月变化及叶片叶绿素和营养元素质量分数的变化规律。结果表明:冠层I、冠层II和冠层III的净光合速率日变化均呈单峰型,且具有明显的分层性,其日均值的大小次序为:冠层III>冠层Ⅱ>冠层I,差异均达显著水平;同一冠层叶片的净光合速率在不同月份之间呈先增大后减小的趋势,7月和8月的净光合速率明显高于5月、6月和9月,同时随冠层的升高净光合速率呈递增的趋势,冠层Ⅱ和冠层III叶片净光合速率均显著高于冠层I;同一冠层4个方位叶片叶绿素质量分数的平均值表现为:冠层III≈冠层Ⅱ>冠层I,即冠层III和冠层Ⅱ未达到显著性差异,但均显著高于冠层I。此外,不同营养元素在杨树叶片中质量分数差异较大,其中氮质量分数较高,而磷元素、钾元素、钙元素和镁元素质量分数较低,并且随冠层的升高,各营养元素质量分数均呈递增的趋势。

An experiment was conducted to determine the diurnal variation and monthly variation of net photosynthetic rate, and contents of chlorophyll and nutrient elements in different canopy. The diurnal variation of net photosynthetic rate in Canopy Ⅰ,Ⅱ,Ⅲ is unimodal type and has obvious stratification. The diurnal average of net photosynthetic rate of the canopy is in an ascending order of Conopy Ⅰ,Ⅱ and Ⅲ, and the differences among different canopy are significant. The leaf net photo- synthetic rate in the same canopy displays the variation tendency of first increases and then decreases in different months, and the net photosynthetic rates in July and August are significantly higher than those in May, June and September. The net photosynthetic rate shows a trend of increasing with the increase of canopy, which the net photosynthetic rates of Cano- py Ⅱ and Ⅲ significantly increase compared with the Canopy Ⅰ. The average value of leaf chlorophyll content for four dif- ferent orientations in the same canopy shows the variation tendency ： Canopy Ⅲ ≈ Canopy Ⅱ〉Canopy Ⅰ. The contents of different nutrient elements in poplar leaves have larger differences, so the nitrogen content is higher, and the elements of phosphorus, potassium, calcium and magnesium content are lower, and the contents of nutrient elements are increasing trend with the increase of canopy.