关键词: 光能利用率, 光补偿点, 光饱和点, 物候期变化

Abstract: We examined the differences of maximum light use efficiency (LUE_max), most effective light intensity (PAR_e), light compensation point (LCP) and light saturation point (LSP) in diffe-rent vertical positions and different phenological periods of tree crown in Larix principis-rupprechtii plantation in Saihanba Mechanical Forest Farm of Hebei Province. We analyzed the main influencing factors for all the variables. The results showed that LUE_max increased with the increasing crown depth, and that PAR_e, LCP and LSP decreased with the increasing crown depth. Such a result indicated that upper crown had higher utilization efficiency to strong light and that the lower crown was more efficient to adapt to weak light environment. During the leaf development in the growth period, the LUE_max approximately increased except in July, while the changes of other photosynthe-tic-light factors showed a tendency of unimodal curve. Environmental factors were significantly correlated with the indices of light response, mainly due to the stress reaction of leaf stomata to surrounding environment. Understanding the spatial and seasonal changes of the photosynthetic-light indicators was important for formulating scientific management measures, optimizing stand structure, improving local microenvironment and maximizing forest productivity.

Key words: light use efficiency, light compensation point, light saturation point, phenological variation