森林光环境对4种乔木幼树光合和光谱反射特性的影响

在林窗、林缘、林下3种自然光环境下，对吉林蛟河阔叶红松林常见树种拧筋槭、白牛槭、色木槭和红松的光合和光谱特性进行对比研究，以期从生理生态角度探讨它们对自然光环境的适应能力和响应机制。结果表明：4种乔木幼树叶片的光饱和点（LSP）和光补偿点（LCP）随着生长环境光强的下降而减小，林下各树种幼树LSP和LCP显著低于林窗内幼树（P<0.05）；除白牛槭外林下其他树种最大净光合效率（P_nmax）均显著小于林窗内幼树（P<0.05）；不同树种幼树表观量子效率（AQY）和暗呼吸速率（R_d）随光环境的变化并没有出现明显的变化规律，各环境间差异较小。除白牛槭外，其他树种幼树叶绿素归一化指数（Chl NDI）随环境光强的减少而增大，林下树种的光化学反射指数（PRI）普遍高于光条件更好环境下树种，说明林下幼树叶片叶绿素含量和光合速率大于其他光环境；各树种植物叶片水分指数（WI）在不同光环境之间存在显著差异，环境光强越大植物叶片WI越小，植物叶片水分浓度越小。林缘下3种槭属幼树结构不敏感植被光谱指数（SIPI）显著小于其他光环境（P<0.05），说明林缘下幼树受到相对较小的环境胁迫。林窗内，红松具有最高的LCP、LSP、P_nmax、R_d和PRI，说明红松具有较高的光合潜力，更加适应高光生长环境，3种槭属中，白牛槭拥有最高的Chl NDI和PRI值，表现出较好的适应性，说明红松和白牛槭能在林窗环境内较好更新并逐步占据林冠层。

Photosynthetic characteristics and spectral reflectance characteristics of four natural tree saplings under forest light environment

To explore the adaptability and response mechanism of plants to natural light environment from the perspective of physiology and ecology, we studied the photosynthetic and spectral characteristics of common tree species (Acer triflorum, Acer mandshuricum, Acer mono, and Pinus koraiensis) in Jilin Jiaohe broad-leaved Korean pine forest under three natural light environments (forest gap, forest edge, and understory). The results showed as follows:the light saturation point(LSP) and light compensation point(LCP) of saplings of the four tree species decreased with the decrease of ambient light intensity, and the LSP and LCP of saplings of all tree species were significantly lower than those of saplings in gap (P<0.05). Except Acer mandshuricum, The maximum net photosynthetic rate(P_nmax) of other tree species was significantly smaller than that of saplings in the gap(P<0.05). The apparent quantum yield(AQY) and dark respiration rate(R_d) of saplings of different tree species did not change significantly with the change of light environment, and there was little difference among different environments. The chlorophyll normalized index (Chl NDI) of sapling trees increased with the decrease of ambient light intensity except Acer mandshuricum. The photochemical reflectance index(PRI) value of understory trees was generally higher than that of trees under better light conditions, indicating that the chlorophyll content and photosynthetic rate of understory trees was higher than that of other light conditions. There were significant differences in the water index(WI)of leaves among different tree species in different light environments(P<0.05), and the WI of leaves decreased with the increase of environmental light intensity, showing that the water concentration of sapling leaves was the lowest under the gap environment.The structure-insensitive pigment index (SIPI) of three acer species at the forest edge was significantly lower than that of other light environments(P<0.05), indicating that the saplings under the forest edge were subjected to relatively little environmental stress.In the forest gap, Pinus koraiensis had the highest LCP, LSP, P_nmax, R_d and PRI, indicating that Pinus koraiensis had higher photosynthetic potential and was more adaptable to high-light growing environment. Among the three acer species, Acer mandshuricum had the highest Chl NDI and PRI values, indicating that it had good adaptability to the light environment in forest gap. These results indicated that Pinus koraiensis and Acer mandshuricum could renew well and occupy the canopy gradually in the gap environment.