火炬树克隆分株与荆条克隆分株的光合日进程差异

Photosynthetic differences between understory clonal ramets of Rhus typhina and Vitex negundo var. heterophylla in Taihang Mountain area of China

研究火炬树Rhus typhina克隆分株与荆条Vitex negundo var. heterophylla克隆分株光合生理生态日变化特征,揭示它们对火炬树单优群落下层与外缘不同光强的生态适应差异。分别火炬树单优群落下层和外缘,比较测定了火炬树与荆条克隆分株的光合日进程。结果表明:①由于光合有效辐射降低,火炬树克隆分株与火炬树单优群落内荆条竞争极为有限的光合有效辐射,群落外缘本土灌木种荆条的净光合峰值为9.183μmol.m-2.s-1,群落内荆条的净光合速率仅为1.396μmol.m-2.s-1,同时荆条净光合速率峰值还低于火炬树克隆分株。②在13:00至17:00,火炬树克隆分株在其单优群落内的Fv/Fm值高于荆条克隆分株,证实火炬树克隆分株适应弱光能力超过荆条。火炬树通过克隆繁殖形成高度的自遮荫现象,是引起火炬树克隆分株与荆条克隆分株之间光合生理生态差异的重要原因。

In the degraded habitat of the hilly Taihang Mountain area, non-native tree species of Staghorn sumac （Rhus typhina） have spread over time forming a number of monodominant communities. In order to understand differences in their ecological adaptation, the physio-ecological diurnal variations from clonal ramets of R. typhina and Vitex negundo var. heterophylla （negundo chastetree）, growing in different light regimes as an understory of a staghorn sumac monodominant overstory and with no overstory, were studied. Based on a field experiment staghorn sumac ramets growing under the staghom sumac overstory more effectively captured low levels of photosynthetically active radiation （PAR） than V. negundo var. heterophylla. So the net photosynthetic rate （Pn） of clonal ramets of V. negundo var. heterophylla was significantly lower than R. typhina （ P ≤0.05 of V. negundo vat. heterophylla growing at the edge of the staghorn sumac monodominant ）. Additionally, Pn community reached a peak of about 9.183μmol· m^- 2 s^-1 at 10 ： 00, while the same species growing beneath the overstory only attained 1. 396 μmol·m^-1·s^-1 When grown under the overstory, the ratio of variable to maximum chlorophyll fluorescence emission （Fv/Fm） from 13： 00- 17：00 was stately higher （P≤0.05） for R, typhina clonal ramets than V. negundo var, heterophflla, meaning that clonal ramets of R, typhina were better adapted to weak light. Thus, shading from an R. typhina ovdrstory caused photosynthetic physio-ecological differences between clonal ramets of R. typhina and V. negundo var. heterophylla.