阔叶红松林林冠空隙光强异质性对红松幼树生长的影响

利用Li-6400光合测定系统，研究了长白山阔叶红松林4个不同尺度林窗内光照强度的异质性，分析红松幼树在林窗内9个方位的光合作用日变化特征.结果表明：林窗内9个方位出现光合有效辐射(PAR)峰值顺序为:西实际林窗、北扩展林窗、林窗中心＞南实际林窗、南扩展林窗、东扩展林窗、东实际林窗＞西扩展林窗、北实际林窗，光照呈东-西、南-北不对称分布，光照梯度在西、北方向变化较大，但各方向距中心不同距离的日均PAR无显著差异.林窗Ⅰ～Ⅳ日均PAR分别为21.85、45.57、66.02和23.48 μmol·m^-2·s^-1，相互之间均达显著差异水平（P＜0.05）.PAR与净光合速率(P_n)呈显著正相关，且相关系数随PAR增大而增大.随林窗面积的增大，PAR和P_n均先增大后减小; 当林窗面积为267 m²时，二者同时达到最大值.

Effects of light intensity heterogeneity in gaps of broadleaved Korean pine forest in Changbai Mountains on Pinus koraiensis seedlings growth.

By using a Li-6400 portable photosynthesis system, this paper studied the heterogeneity of light intensity in four different size gaps of a broadleaved Korean pine forest in Changbai Mountains, and analyzed the diurnal change of the photosynthesis of Pinus koraiensis saplings in the gaps. In the nine orientations within the gaps, the peak value of the photosynthetically active radiation (PAR) varied in the sequence of west of actual gap, north of extended gap, gap center＞south of actual gap, south of extended gap, east of extended gap, east of actual gap＞west of extended gap, north of actual gap. Light distribution was dissymmetry in the orientations of east-west and south-north, with the variation in west and north being more significant than that in other orientations. There was no significant difference in the average PAR among the positions within specific orientations. The average PAR of the four gaps from I to IV was 2185, 4557, 6602, and 2348 μmol·m-2·s-1, respectively, and the difference was statistically significant (P＜005). PAR had a significant positive correlation with net photosynthetic rate (Pn), and the correlation coefficient increased with increasing PAR. With the increase of gap size, both the PAR and the Pn of P. koraiensis saplings increased first and decreased then, with the maximum values appeared at 267 m2 of gap size .