西双版纳热带季节雨林热力效应时空分布特征初探

Temporal and spatial distribution characteristics of thermal effects in a tropical seasonal rainforest in Xishuangbanna, southwest of China.

该文利用西双版纳雾凉季和干热季的气温和树表温观测资料 ,通过实测、对比方法 ,探讨了热带季雨林平均气温及其树表温的时空分布特征 .通过对分布特征和变化规律的分析、研究 ,发现由于热带季节雨林受地方气候和森林结构影响 ,不同区域、不同时间受到太阳辐射影响的差异 ,导致气温和树表温均存在明显的时空差异 ,在林冠附近 ,树冠表温和气温及温度日较差均呈现最大值 ,显示了林冠面具有较强的热力效应 ,且其效应在干热季显著 .在 12 :0 0— 16 :0 0 ,树冠附近空气与树冠表层间的热力传输 ,雾凉季树冠附近气温低于林冠表温 ,热量从树冠传向空气 ;而干热季则反之 ,树冠附近气温高于林冠表温 ,林冠从空气中获得热量 .林内的第二冠层上午和下午气温多高于树冠表温 ,中午前后气温低于树冠表温 ,并且干热季的温差的绝对值大于雾凉季 ;而在林内近地冠层热量多是由树冠传向近旁空气 ,显示了热力传输的时空多变特征 .热带季节雨林林内树表温和气温多呈现逆温分布 ;上午树表面为热源 ;中午则反之 ,多是空气为热源 ;而下午树表面与空气多处于热平衡状态 .热带季节雨林中热力作用复杂、多样 ,使得热力效应时空分布趋于多样化 。

Based on observation data in the fog-cool and dry-hot seasons, the temporal and spatial distribution characteristics of air temperature and trunk surface temperature of tropical seasonal rainforest in Xishuangbanna were studied. It is found that air temperature and trunk surface temperature present obviously temporal and spatial differences influenced by local climate, forest structure and solar radiation variation in different sites and time. The trunk surface temperature, air temperature and daily air temperature difference all reach maximum near the forest canopy, which shows that the forest canopy possesses stronger thermal effect; moreover, it is significant in dry-hot season. Around the canopy, the directions of thermal transfer between the air and forest canopy surface are opposite in fog-cool and dry-hot season from 12:00 to 16:00. In fog-cool season, the air temperature is lower than canopy surface temperature, which makes heat transfer from canopy surface to air; while it is quite the contrary in the dry-hot season. The air temperature is almost higher in the morning and afternoon, but lower around the noon than canopy surface temperature at the height of the second canopy in the forest; moreover, the absolute values of temperature difference are bigger in the dry-hot season than those in the fog-cool season; near ground, the heat is often transferred from the canopy to the surrounding air, which indicates that temporal and spatial variability characteristics of heat transfer. There often exhibits phenomenon of trunk surface temperature and air temperature inversion in the tropical seasonal rain forest. The trunk surface is a hot source in the morning, while at noon the air turns to a hot source and there keeps heat equilibrium between the trunk surface and the air in the afternoon. Thermal effect of tropical seasonal rain forest is so complicated and multiform that makes thermal effect distribution diversification and induces microclimatic environment heterogeneity.