为了阐明不同径级白桦(Betula platyphylla)树干液流变化对不同土壤水分条件的响应差异,以期为揭示白桦树种对土壤水分的利用策略以及该地区生态恢复过程中水分循环机制研究提供参考。在2017年5月初—9月末,运用Granier热扩散边材树干液流探针(TDP)对白桦进行树干液流观测,并同步监测太阳辐射、空气温度、空气相对湿度、降雨量等气象因子及土壤水分动态,分析大兴安岭南段白桦树干液流特征对气象因子及土壤水分动态的响应。结果 表明:非阴雨天气下液流密度日变化在土壤含水量相对充足和相对亏缺时表现为昼高夜低,与太阳辐射、空气水汽压亏缺变化较为一致。同一土壤含水量条件下两个径级液流密度差异显著,表现为大径级高于小径级; 同一径级下表现为土壤含水量相对充足大于相对亏缺时。在不同土壤含水量时期采用饱和指数曲线分别对液流密度与太阳辐射和空气水汽压亏缺进行拟合,拟合效果可以较好地反映出液流密度对气象因子的响应规律。不同土壤含水量下白桦气孔蒸腾作用对土壤含水量变化具有较高的敏感性。
In order to clarify the response of changes in stem sap flow of Betula platyphylla with different diameter classes to different soil water conditions, and provide reference for revealing the utilization strategies of Betula platyphylla for soil water and the study of water cycle mechanism in the process of ecological restoration in this area, from early May to late September 2017, the sap flow of Betula platyphylla in Saihanwula area, southern Greater Xing'an Mountains, Inner Mongolia, was observed by using Granier thermal diffusion sap flow probe, and the meteorological factors such as solar radiation, air temperature, air relative humidity and rainfall were monitored synchronously. The response of stem sap flow characteristics of Betula platyphylla to meteorological factors and soil moisture dynamics was analyzed. The results showed that the diurnal variation of sap flow density in non-rainy weather was higher in the daytime and lower in night when soil moisture content was relatively sufficient and relative deficient, which was consistent with the variation of solar radiation and air vapor pressure deficit; under the same water condition, the sap flow densities of the two diameter classes was significantly different, the sap flow density of large diameter class was higher than that of the small diameter class; under the same diameter class, the sap flow density under relatively sufficient soil water content was greater than that under the relatively deficient soil water content; Saturation exponential curve was used to fit the sap flow density with solar radiation and air vapor pressure deficit, respectively, which can better reflect the response of sap flow density to meteorological factors. The stomatal transpiration of Betula platyphylla was highly sensitive to the change of soil water content under different soil water contents.
