林窗面积对香椿生长及光合生理特性的影响

Effects of forest gap size on growth and photosynthetic characteristics of Toona sinensis

研究了川中丘陵区柏木人工林内人造林窗面积[50 m2(Ⅰ),100 m2(Ⅱ)和200 m2(Ⅲ),旷地(CK)]对香椿生长、光合特性及相关生理特征的影响。结果表明:林窗面积对香椿的树高、地径和冠面积影响显著,以林窗Ⅱ最大,CK最小;随着林窗面积的增加,香椿的日均净光合速率增加,但午时的净光合速率初始量子效率、近光饱和点、最大净光合速率、光氮利用率、光能利用效率都显著降低,光合能力下降;香椿的叶绿素a/b、叶片厚度、比叶鲜重、比叶干重、单位面积叶氮含量、丙二醛、超氧化物歧化酶及可溶性蛋白含量随着林窗面积的增加而增加,而叶绿素a、叶绿素b和类胡萝卜素含量都降低,表明香椿对因林窗面积变化而导致的光强改变有较强的适应性,这在一定程度上促进了生长及光合能力的差异;旷地内香椿的"光合午休"及林窗内日均Pn的降低可归因于非气孔因素限制。说明香椿对生境的变化适应性较强,而且100 m2的林窗在其形成初期能有效促进香椿维持较高的生产力和光合能力。

To study the growth,photosynthetic characteristics and physiological of Toona sinensis under different sizes of forest gaps,to know the response of the light intensity,we were selected three different size of forest gaps including 50 m^2（Ⅰ）,100 m^2（Ⅱ）,200 m^2（Ⅲ）and opening field（CK）,which were in a cypress plantation in hilly region of central Sichuan.The results showed that the plant height,stem diameter,crown area of Toona sinensis were significantly influenced by increased of gap size.The three properties in opening field were significantly lower than which in other size of forest gaps,and those properties in gap Ⅱ were the largest.The net photosynthetic rate at noon,intrinsic quantum efficiency,light saturation point,highest maximum net photosynthetic rate,photosynthetic nitrogen utilization efficiency,light use efficiency,chlorophyll a /b,leaf thickness,leaf fresh mass per unit leaf area,leaf dry mass per unit leaf area,nitrogen in per unit area,malondialdehyde,superoxide dismutase,soluble protein increased with the increase of gap size.On the contrary,the net photosynthetic rate of day,chlorophyll a,chlorophyll b,carotenoids decreased.So the photosynthetic capacity of Toona sinensis decreased with the increase of gap size,and to some extent had a positive effect on differences of photosynthetic capacity and growth.We speculated that non-stomatal limitation was the main factor that ＂ photosynthetic siesta＂ and inhibited net rate.Therefore,Toona sinensis had a good adaptability to environment and Toona sinensis could keep a high photosynthetic capacity and productive forces in gap Ⅱ at the initial stage of gap formation.