环境因子对大兴安岭南段白桦树干液流变化特征的影响

Effect of Environmental Factors on Characteristics of Sap Flow of Betula platyphylla in Southern Daxing’an Mountains

为揭示半干旱区大兴安岭南段白桦(Betula platyphylla)树干液流变化特征及其对环境因子的响应,以该地区赛罕乌拉国家级自然保护区的主要树种白桦为对象,在2019年6月初至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,并利用WS1000自动气象站同步监测太阳辐射、空气温度、空气相对湿度等环境因子,分析白桦树干液流特征及其对环境因子的响应。结果表明:各月的日累计液流密度值由大到小依次为7月(70.769 5 cm3·cm-2·d-1)、8月(69.045 9 cm3·cm-2·d-1)、9月(67.955 3 cm3·cm-2·d-1)、6月(57.292 4 cm3·cm-2·d-1)。液流密度日变化表现为单峰曲线,总体变化规律为昼高夜低。液流密度与各环境因子相关系数由大到小依次为太阳辐射Rs(0.837)、空气温度Ta(0.608)、空气水汽压亏缺VPD(0.589)、空气相对湿度RH(0.453),并且均达到极显著检验水平(P<0.01),在7月时液流密度对林内小气候有极显著响应。采用多元线性回归分析建立液流密度与各环境因子的回归方程的决定系数R2=0.747,拟合度较高,总体回归效果显著,且模拟值与实测值动态变化规律较为一致,绝对误差为8.76%。白桦树干液流密度对太阳辐射以及空气温度的变化具有较高敏感性,液流密度与各环境因子之间存在显著线性相关性。

The experiment was conducted to reveal the characteristics of sap flow of Betula platyphylla and its response to environmental factors in Southern Daxing’an Mountains, a semi-arid area, with the main tree species of B. platyphylla in Saihanwula National Nature Reserve. During the period from the beginning of June to the end of September 2019, the stem sap flow of B. platyphylla was measured by using Granier TDP was used to observe the sap flow of B. platyphylla, and WS1000 automatic weather station was used to synchronously monitor the environmental factors such as solar radiation, air temperature and air relative humidity. The daily accumulative sap flow of each month was in the descending order of July(70.769 5 cm3·cm-2·d-1), August(69.045 9 cm3·cm-2·d-1), September(67.955 3 cm3·cm-2·d-1) and June(57.292 4 cm3·cm-2·d-1). The daily variation of sap flow shows a single peak curve, and the overall variation law is high in the day and low in the night. The correlation coefficients between the density of sap flow and the environmental factors in the descending order were Rs(0.837), Ta(0.608), VPD(0.589) and RH(0.453), which all reached the extremely significant test level(P<0.01). In July, the sap flow had a significant response to the forest microclimate. By using multiple linear regression analysis to establish the regression equation of sap flow and environmental factors, the decision coefficient R2 of 0.747, the fitting degree was high, the overall regression effect was significant, and the dynamic change rule of the simulation value and the measured value was relatively consistent, the absolute error was 8.76%. The response of sap flow of B. platyphylla to solar radiation and air temperature is obvious, and it has high sensitivity to the changes of both. There was a linear correlation between sap flow and environmental factors.