3种乔木叶片反射光谱与光合特性随树高的变化

Changes in Leaf Spectral Reflectance and Photosynthetic Characteristics with Tree Height in Three Tree Species

树木生长到一定高度阶段,顶部叶片会受到水分运输阻力的影响,表现为叶片水分亏缺,进而引发其他生理特性的变化.本研究比较了阔叶红松林3种高大乔木(蒙古栎Quercus mongolica、紫椴Tilia amurensis、红松Pinuskoraiensis)不同高度植株叶片的反射光谱特征(光谱反射率R、光化学反射指数PRI)和光合特性(光合速率Pn、蒸腾速率Tr、气孔导度Cond)的变化.结果表明:随树木高度增加,蒙古栎和紫椴叶片的PRI和各项光合参数先升高后下降,各高度间差异显著(P<0.05);红松的各项参数则随树高增加而增加,无下降趋势.分析表明,蒙古栎和紫椴高树Pn的下降很可能受到缺水胁迫的影响,但由于物种间可能存在不同的气孔调节机制,红松未表现出水分亏缺.另外,蒙古栎和紫椴的PRI指数与其Pn成显著正相关关系(分别为r2=0.986、0.890),但在红松叶片中PRI指数并不能反映Pn的变化,表明在使用PRI指数监测植物光合能力时要考虑物种间的差异.

As tree grows high, leaves in the top are always affected by water transport resistance, which leads to water deficiency. Accordingly, the biological characteristics of leaves also change. In this paper, 3 tree species （Quercus mongolica, Tilia amurensis, and Pinus koraiensis） were observed to study the relationship between leaf spectral reflectance （spectral reflectance R, photochemical reflectance index PRI） and photosynthetic characteristics （photosynthetic rate Pn, transpiration ratio Tr and stomata conductance Cond） with different tree height. The results showed that PRI and photosynthesis in Q. mongolica and T. amurensis had a trend of increasing at the first and decreasing later with tree height. Their variations were significant at different heights （P〈0.05）. In contrast, these indexes of P. koraiensis showed constant increase with tree height. The results indicated that water deficit affected more intensely the leaf photosynthesis in the top of the first 2 tree species than P. koraiensis, probably because of different stomatal regulation mechanism. Additionally, there was a significantly positive relationship between leaf PRI and Pn in Q. mongolica and T. amurensis （r2=0.986, 0.890）. However, PRI could not reveal the changes of Pn in P. koraiensis, which suggested that PRI should be used in combination with species difference. Fig 3, Tab 1, Ref 26