论文部分内容阅读
冠层气孔导度(g_s)是衡量冠层-大气界面水汽通量的重要生物学常数,研究其特征及对环境因子的响应,能为开展森林冠层水汽交换过程的机理性研究提供理论依据.于2014年利用SF-L热扩散式探针测定了侧柏的树干液流密度(J_s),同步监测光合有效辐射(PAR)、饱和水汽压差(VPD)、气温(T)等环境因子,计算侧柏的冠层气孔导度特征并分析其对各环境因子的响应.结果表明:侧柏液流密度的日变化总体呈双峰曲线,生长季高于非生长季,且胸径越大液流密度越大;冠层气孔导度日变化与单位叶面积冠层蒸腾(E_L)趋势相近,均呈双峰曲线,生长季的冠层气孔导度和蒸腾较非生长季略高.侧柏冠层气孔导度与空气温度呈抛物线关系,在10℃左右冠层气孔导度达到峰谷;光合有效辐射以400μmol·m~(-2)·s~(-1)为界,小于该阈值两者呈正相关关系,大于该阈值则冠层气孔导度受其影响较小;与饱和水汽压差呈负对数函数关系,随饱和水汽压差增大而逐渐降低.较高的空气温度和光合有效辐射、较低的饱和水汽压差有利于侧柏形成较大的冠层气孔导度,进而促进冠层蒸腾.
The canopy stomatal conductance (g_s) is an important biological constant to measure the water vapor flux at the canopy-atmosphere interface. Studying its characteristics and its response to environmental factors can provide a theoretical basis for studying the mechanism of water vapor exchange in the canopy In 2014, SF-L thermal diffusive probe was used to determine the sap flow density (J_s), simultaneous monitoring of environmental factors such as photosynthetically active radiation (PAR), saturated vapor pressure (VPD) and temperature , Calculated the canopy stomatal conductance characteristics of canopy and analyzed their responses to various environmental factors.The results showed that the diurnal changes of the flow density of oriental arborvitae showed a bimodal curve in general with the growing season being higher than the non-growing season and the larger the diameter at breast height The greater the liquid flow rate, the greater the diurnal variation of stomatal conductance and the trend of canopy transpiration (E_L) per unit leaf area, showing a bimodal curve with a slightly higher canopy stomata conductance and transpiration in the growing season than in the non-growing seasons. The stomatal conductance of the canopy had a parabolic relationship with the air temperature. The stomatal conductance reached the peak and valley at about 10 ℃. The photosynthetically available radiation was bounded by 400 μmol · m -2 · s -1, The two thresholds showed a positive correlation, and above the threshold, the canopy stomatal conductance was less affected. Compared with the saturated The vapor pressure difference showed a negative logarithm function, which gradually decreased with the increase of the pressure difference of saturated water vapor.The higher air temperature and photosynthetically active radiation, the lower saturated vapor pressure difference was conducive to the formation of a larger canopy stomatal conductance Degrees, which in turn promote canopy transpiration.