I-69杨不同冠层叶片光合能力与营养元素的时空特征

Spatial and temporal characteristics of photosynthetic capacity and nutrient concentrations in different canopy layers of poplar I-69

以I-69杨(Populus deltoides Bartr.cv.‘Lux’)为研究对象,观测了不同冠层的小气候特征、叶片光合特性、光合叶面积和营养元素,并对不同冠层叶片生长状况作综合评价。结果表明,I-69杨光合特性在7、8月要好于5、9月,叶片净光合速率、平均单叶面积和单层叶面积都是冠层Ⅲ>冠层Ⅱ>冠层Ⅰ;不同冠层叶片营养元素含量随月份不同而发生变化,氮含量和磷含量从6月至10月整体上呈下降趋势,钾含量在8月前呈上升趋势,到8月后逐渐下降,钙含量则从6月至10月呈上升趋势;距离综合评价法算得冠层Ⅰ、Ⅱ、Ⅲ的相对接近度依次为0.163、0.625和0.785,表明不同冠层叶片生长状况差异显著,即冠层Ⅱ、Ⅲ叶片生长状况明显优于冠层Ⅰ。

Microclimate, photosynthetic characteristics, photosynthetic area and nutrient concentrations in different canopy layers were measured to make a comprehensive evaluation of leaves growth for poplar I-69（Populus deltoides Bartr. cv. ‘Lux’）. The results showed that the photosynthetic characteristics were better in July and August than in May and September. The net photosynthetic rate, average area of single leaf and leaf area of single layer were in the order of canopy layer III〉 canopy layer II 〉canopy layer I. Foliar nutrient concentrations in the different canopy layers varied with the month. Nitrogen and phosphorus concentrations appeared an overall downward trend from June to October. Potassium concentration increased before August and after then decreased gradually. Calcium concentration showed the upward trend from June to October. The relative approach degree calculated by TOPSIS for canopy layer I, II, III were 0.163, 0.625 and 0.785, respectively, indicating that the leaves growth condition of the different canopy layers were significantly different. The growth condition of leaves in canopy layer II and III were obviously better than that in canopy layer I.