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植物温度是森林生态系统能量平衡和植被呼吸估算的重要参数.采用T型热电偶监测树皮和木材特性各异的2个阔叶树种(白桦和水曲柳)不同深度、高度和方位的树干温度(T_s),探索T_s日变化的空间变异及其影响因素.结果表明:T_s月平均日变化格局与空气温度呈相似的正弦曲线,但T_s变化滞后于空气温度,时滞从树皮表面处的0 h增加到6 cm深度处的4 h.随测定深度的增加和高度的降低,T_s日变化的峰值和日较差均逐渐减小.T_s周向差异不大,休眠季节白天南向、西向T_s日峰值略高.两树种树皮和木材的热学特性(比热容和导热系数)的差异,会通过影响树干表面与外界的热交换和树干内部热扩散而造成T_s径向变化的种间差异.白桦树皮较高的反射率削弱了太阳辐射对T_s的影响.多元逐步回归分析表明,环境因子可以很好地估测T_s日动态(R~2>0.85),影响程度依次为空气温度>水汽压>净辐射>风速.估算生物量热储和树干表面CO2通量时应考虑T_s径向、纵向和种间差异.
Plant temperature is an important parameter for energy balance and vegetation respiration estimation in forest ecosystems.Two broad-leaved tree species (Betula platyphylla and Fraxinus mandshurica) with different tree bark and wood characteristics were monitored by T-type thermocouple at different depths, altitudes and orientations (T_s) to explore the spatial variability and its influential factors of diurnal variation of T_s.The results show that the average daily diurnal variation of T_s is similar to the air temperature, but the variation of T_s lags behind the air temperature, 0 h increased to 6 cm depth 4 h. With the increase of the depth and the decrease of the height, the peak value and diurnal variation of T_s decreased gradually. There was no significant difference in T_s between the south and west during the dormancy season The difference between the thermal characteristics (specific heat capacity and thermal conductivity) of the bark and the wood of the two species caused the interspecific variation of T_s in the radial direction by affecting the heat exchange between the tree trunk surface and the outside and the heat diffusion inside the tree trunk. The higher reflectivity of birch bark attenuates the effect of solar radiation on T_s.The multivariate stepwise regression analysis shows that the environmental factors can well predict the T_s daily dynamic (R ~ 2> 0.85), with the order of air temperature> water vapor Pressure> Net Radiation> Wind Speed T_s Radial, Longitudinal and Interspecies Differences should be taken into account when estimating biomass heat storage and trunk surface CO2 fluxes.