青冈常绿阔叶林内的小气候特征

FEATURES OF THE MICRO CLIMATE IN THE EVERGREEN BROAD LEAVED FOREST DOMINATED BY Quercus glauca

分析我国中亚热带东部青冈（Ｑｕｅｒｃｕｓｇｌａｕｃａ）常绿阔叶林内的小气候特征，１９９３～１９９５年的研究结果表明：①到达青冈林的总太阳辐射为３３４４７８０ｋＪ／（ｍ２·ａ），四季中群落的反射率、透射率和吸收率分别为１６％～２２％、９％～１２％和６７％～７４％。②林冠外上方及群落上层气温在白天高于群落下层，夜间低于群落下层，可相差３～５℃，夏季差异最大。③林内外空气相对湿度的日动态呈“Ｕ”型变化，林内夜间湿度高达９０％左右，午间较低，在５０％左右。在四季的晴天中，林冠上方的空气相对湿度均低于林内，相差５％～２２％，夏季和冬季差异最大。④林中的ＣＯ２浓度在林冠层最低，近地面层最高，各季节始终低于林外，其中夏、秋两季最明显。⑤在春、夏、秋３季中，土壤温度为白天高于夜间，而冬季则为夜间高于白天；土壤湿度以冬、春季较高（３１．９％和２８．５％），夏季最低（１４．２％）。由于青冈次生林的叶面积指数较小，群落结构较简单，因而整个群落的透光系数较大，群落内外空气温湿度的差异也较小。

The main features of the micro climate in the evergreen broad leaved forest dominated by Quercus glauca in the east of mid subtropical zone of China were studied.Results of 1993～1995 showed that:①The amount of the total solar radiation reached the forest was 3344780 kJ/(m 2·a).In a year,the reflection rate,transmission rate and absorbent rate of the community were 16%～22%,9%～12% and 67%～74%.②The air temperature in day was:above tree canopy>in tree canopy>lower layer in the forest,but in night was on the contrary to the day.The air temperature above the canopy had 3～5℃ of difference to that in the forest,and the greatest difference occured in summer.③The diurnal variations of air relative humidity ( RH ) was in the shape of “U”.In night,the RH was as high as 90% while in the day it was only 50%.In the clear days of 4 seasons,the RH above the tree canopy was lower than that in the forest and the difference between in and out the forest was 5%～22%. The greatest difference also occured in summer and winter.④CO 2 concentration in the forest was lower than that out the forest,the lowest was in the tree canopy,the highest was near the ground surface in the forest,especially in the summer and autumn.⑤In spring,summer and autumn,the soil temperature in day was higher than in night,while in winter it was reverse.The soil water status was higher in winter and spring(31 9% and 28 5% of dry soil),and was the lowest in summer(14 2).Since the LAI of the forest dominated by Quercus glauca in Zhejiang was low nowadays,the structure of the community was simple,so the transmission of light was high,and the differences of the temperature and humidity between in and out the forest were not so great.That reflected it was in the transitional peroid from young growth to the middle aged forest.