半干旱区华北落叶松林冠层蒸腾特征及其影响因子

准确量化半干旱区森林植被耗水特征及其影响因子对植被-水-土的综合管理至关重要。选择内蒙古大青山的华北落叶松人工林为研究对象，利用热扩散探针法监测树干液流，同步监测气象因子和土壤体积含水量。结果表明，研究期间华北落叶松冠层蒸腾存在明显月、季节变化，冠层蒸腾季节变化呈单峰曲线，冠层月蒸腾量（mm）为8月（55.08）＞7月（54.76）＞6月（48.76）＞5月（43.13）＞9月（40.20）＞10月（12.36）。华北落叶松林冠层蒸腾与气温、太阳辐射、大气湿度、饱和气压差、风速、土壤水分均存在极显著相关关系（P＜0.01），回归分析表明气温、太阳辐射和大气湿度是影响冠层蒸腾的主要气象因子；基于边界线的分析表明，冠层蒸腾随太阳辐射、气温变化可用对数增长函数拟合，即随太阳辐射、气温增大，冠层蒸腾先快速后缓慢增大，达到阈值后趋于平稳；冠层蒸腾随大气湿度增加的变化遵循抛物线曲线，阈值为59.41%。次降水量对冠层蒸腾的影响存在差异，降水强度>10 mm的次降水量显著影响华北落叶松人工林冠层蒸腾。总体来看，气温、太阳辐射、大气湿度和降水是影响华北落叶松冠层蒸腾的主要环境因子。

Transpiration Characteristics of Larix principis-rupprechtii Plantation and Its Impact Factors in the Semi-Arid Area

Forest transpiration is a major part in water balance of forestlands.Larch (Larix principis-rupprechtii) plantations located in the Daqing Mountains in Inner Mongolia was set to accurately quantify the characteristics of plantation transpiration and its response to environmental factors which is very important for vegetation-water-soil integrated management in semi-arid region.The sap flow,soil water content and meteorological factors were measured simultaneously from May to October 2016.It was found that larch stand transpiration had obvious seasonal and month variations during the study period.The seasonal variations of transpiration showed a single peak curve.The month forest transpiration (mm) was with an order of August（55.08(＞July(54.76)＞June(48.76)＞May(43.13)＞September(40.20)＞October (12.36).The correlations between larch stand transpiration and air temperature,solar radiation density,air relative humidity,saturated vapor pressure deficit,wind speed and soil moisture were extremely significant (P＜0.01).Regression analysis showed that the dominant meteorological factors which affected the stand transpiration were air temperature,solar radiation density,and air relative humidity.Based on the upper boundary line analysis,the transpiration followed the logarithmic equation with the increase of air temperature and solar radiation density.The transpiration variation showed a trend of fast-slow increase.The transpiration relationship to air relative humidity presented a quadratic equation with a threshold value of 59.41%.The effect of precipitation events on canopy transpiration was different,and the effect was significant when precipitation was above 10 mm.Generally,air temperature,solar radiation density,air relative humidity and precipitation were the main environmental factors that affected the transpiration.