Li Meng, Duan Wen-biao, Chen Li-xin
College of Forestry, Northeast Forestry University, Harbin 150040, China.
Ying Yong Sheng Tai Xue Bao. 2009 Dec;20(12):2853-60.
A continuous measurement of photosynthetic photon flux density (PPFD), air temperature, and relative air humidity was made in the forest gap in primary Pinus koraiensis-dominated broadleaved mixed forest in Xiao Xing' an Mountains to compare the spatiotemporal distribution patterns of the parameters. The diurnal maximum PPFD in the forest gap appeared between 11:00 and 13:00 on sunny and overcast days. On sunny days, the maximum PPFD during various time periods did not locate in fixed locations, the diurnal maximum PPFD occurred in the canopy edge of northern part of the gap; while on overcast days, it always occurred in the center of the gap. The mean monthly PPFD in the gap was the highest in June and the lowest in September, with the largest range observed in July. The maximum air temperature happened between 9:00 and 15:00 on sunny days, between 15:00 and 19:00 on overcast days, the locations were 8 m in the southern part of gap center both on sunny and overcast days. From 5:00 to 9:00, the air temperature at measured positions in the gap was higher on overcast days than on sunny days; but from 9:00 to 19:00, it was opposite. The mean monthly air temperature was the highest in June, and the lowest in September. The maximum relative humidity appeared between 5:00 and 9:00 on sunny and overcast days, and occurred in the canopy border of western part of the gap, with the relative air humidity on overcast days being always higher than that on sunny days. The mean monthly relative humidity was the highest in July, and the lowest in June. The heterogeneity of PPFD was higher on sunny days than on overcast days, but the heterogeneities of air temperature and relative humidity were not obvious. The maximum PPFD, air temperature, and relative humidity were not located in the same positions among different months during growing season. For mean monthly PPFD and air temperature, their variation gradient was higher in and around the center of gap; while for mean monthly relative humidity, it was higher in the edge of forest gap.
在小兴安岭以红松为主的原始阔叶混交林的林隙中，对光合光子通量密度（PPFD）、气温和相对空气湿度进行了连续测量，以比较这些参数的时空分布模式。在晴天和阴天，林隙中的日最大PPFD出现在11:00至13:00之间。晴天时，不同时间段的最大PPFD并不位于固定位置，日最大PPFD出现在林隙北部的冠层边缘；而阴天时，它总是出现在林隙中心。林隙中月平均PPFD在6月最高，9月最低，7月观测到的范围最大。晴天时最高气温出现在9:00至15:00之间，阴天时出现在15:00至19:00之间，晴天和阴天时位置均在林隙中心南部8米处。从5:00至9:00，林隙中测量位置的气温阴天高于晴天；但从9:00至19:00，情况相反。月平均气温6月最高，9月最低。晴天和阴天时，最大相对湿度均出现在5:00至9:00之间，且出现在林隙西部的冠层边界，阴天时的相对空气湿度总是高于晴天。月平均相对湿度7月最高，6月最低。晴天时PPFD的异质性高于阴天，但气温和相对湿度的异质性不明显。生长季节不同月份，最大PPFD、气温和相对湿度不在同一位置。对于月平均PPFD和气温，其变化梯度在林隙中心及其周围较高；而对于月平均相对湿度，在林隙边缘较高。
