光照条件对蒙古栎幼苗生长及形态特征的影响

The impacts of light conditions on the growth and morphology of Quercus Mongolica seedlings

对生长于不同光照环境(林内和林外)下的蒙古栎幼苗的形态特征进行了比较。结果表明,光照条件对蒙古栎幼苗的生物量及其分配具有明显影响,林外幼苗单株生物量为林外的4.48倍,其中以根系生物量的差别为最大,林外为林内的6.23倍;林外与林内幼苗根冠比分别为2.70和1.11。在不同的光照条件下,蒙古栎幼苗的叶片形态表现出明显不同,林外叶片比叶面积明显低于林内,分别为139.55cm2/g和284.94cm2/g,林内约为林外的2.04倍;一次生长叶面积林外明显低于林内,总叶面积则高于林内。二次生长使蒙古栎幼苗的叶面积有明显增加,但是经过二次生长后,幼苗的单株生物量没有明显增加,说明二次生长叶片对于蒙古栎幼苗生物量的积累没有明显贡献;光照对于蒙古栎主干及根系的形态具有明显影响,林外幼苗高(包括二次生长)明显低于林内幼苗,而地径则相反,林外幼苗根系的长度和直径则明显高于林内幼苗;林外幼苗顶芽体积明显大于林内幼苗。同时,林外幼苗的二次生长导致顶芽体积明显下降,从而对翌年的高生长量和未来干型产生影响。认为,蒙古栎幼苗通过形态上的一系列可塑性变化来适应不同的光环境以获取最大的碳收益。

In order to understand how morphological characteristics of Quercus light conditions, we measured differences in dry mass per plant, height growth , root-to-shoot ratio, specific leaf area （ SLA）, and the volume of apical bud across both seedlings growing under forest canopy and open field. Our data indicated that light conditions significantly influenced the morphological characteristics of Quercus Mongolica seedlings. The dry mass per plant in open-field seedlings was 4.48 times as that in undergrowth seedlings. There was a larger difference in root mass as compared to shoot mass, in which the root mass of open-field seedlings was 6.23 times as that of undergrowth seedlings The root-shoot ratio was 2.70 and 1.11 for open-field and undergrowth seedlings, respectively. The SLA was lower in the open-field site （139.55cm^2/g） than in the undergrowth site （284.94cm^2/g）. The area of first-flush leaves was lower in the open-field site than in the undergrowth site, but the total leaf area including first- and second-flush leaves of a plant indicated an opposite pattern. Although the second-flush leaf growth led to an increase of leaf area, there was no difference in total dry mass per plant between seedlings with and without second-flush leaf growth, suggesting that second-flush leaves did not contribute to biomass accumulation of a plant. The height growth was significantly lower in open-field seedlings than in undergrowth seedlings, but the basal stem diameter showed an opposite pattern. The length and diameter of roots and the volume of apical buds were typically larger in the open-field site than in the undergrowth site. The second-flush leaf growth led to a decrease in the volume of apical buds of open-field seedlings, which might affect the height growth of next year. We concluded that Quercus Mongolica seedlings plastically adapt to different light conditions through changes in morphological characteristics to maximize carbon gain.