中文摘要：

对川西亚高山白桦林（海拔2540m）内太阳辐射、空气温湿度以及土壤5cm和15cm层温度等进行了连续的定位观测．结果表明：1）林冠下的太阳辐射日进程与林冠上的不同，但辐射强度随着太阳高度角的变化而变化；林冠下太阳辐射日总量不仅受林冠上辐射日总量的影响，也受森林群落生长季节的影响；春、夏和秋季，林冠下平均辐射日总量分别占林冠上平均辐射日总量的53．1％、39．4％和55．8％，2）夏季，白天空气温度高于土壤温度，而夜间则相反；空气温度和土壤温度的日极端温度出现的时间不同步，空气温度对太阳辐射强度的敏感性比土壤温度的敏感性高．3）春季，土壤表层〉4℃的积温高于空气和土壤底层〉4℃的积温；夏季，〉4℃的积温由高到低的次序为：林冠下空气〉土壤5cm层〉土壤15cm层，而秋季的比较结果与之相反；空气日平均温度与土壤日平均温度有显著的线性关系（P〈0．001）．4）林冠下的空气相对湿度（RH）比林冠上的高，林冠下的空气RH日变幅和季节性变幅比林冠上的小．图7表1参19

英文摘要：

Solar radiation, air temperature, air relative humidity and soil temperature of different soil layers within the subalpine birch forest （ elevation 2 540 m ） located at the Wanglang National Nature Reserve [ （ A （ E ） 103°55＇ ～ 104°10＇, φ（ N ） 32°49＇～ 33°02＇] in western Sichuan, were continuously observed in situ from June 2002 to May 2003. The main results showed ： 1 ） Daily course of solar radiation under canopy and over canopy was markedly different, and the intensity of solar radiation under canopy and over canopy was mainly controlled by the solar altitude. Total radiation of a day under canopy was influenced by solar altitude and air transparence. It was also influenced by forest structure because the forest structure, and leaf area and characteristics were different in different seasons. In spring, summer and fall, the mean total radiation of a day under canopy was reduced by 53.1% , 39.8% and 55.8% , respectively. 2） In summer, the diurnal air temperature was higher than soil temperature, but the nightly air temperature was lower than soil temperature. With the increase of solar radiation, the air and soil temperature also increased. The arisen time of extreme air and soil temperatures were significantly different. The sensitivity of air temperature to solar radiation was stronger than that of soil temperature. 3 ） In spring, degree-day 〉 4 ℃ of soil 5 cm layer was higher than that of air and soll 15 cm layer. In summer, degree-day 〉4 ℃ of air was higher than that of soil 5 cm and 15 cm layers. But in fall, degree-day 〉4 ℃ of soil 15 cm layer was higher than that of air and soll 5 cm layer. The line correlation between daily mean air temperature and soil temperature were markedly significant （P 〈 0. 001 ）. 4 ） The air relative humidity under canopy was higher than that over canopy. Furthermore, the daily and seasonal change range of air rela- tive humidity under canopy was lower than that of air relative humidity over canopy. Fig 7, Tab 1, Ref 19