模拟干旱下杨树树干液流特征及其对环境因子的响应

Characteristics of Poplar Populus deltoides Stem Sap Flow and Its Response to Environmental Factors Under Simulated Drought

[目的]研究干旱对杨树人工林树干液流的影响,可以深入理解杨树人工林对全球降水格局改变的响应。[方法]于2018年9月—2020年11月以东台林场10年生杨树(Populus deltoides)人工林为对象,采用穿透雨移除法模拟干旱处理:CK(对照)、D_(1)(30%穿透雨移除)、D_(2)(50%穿透雨移除),利用热扩散探针技术连续测定杨树人工林的液流变化,结合同步监测的环境因子,揭示杨树人工林对环境因子的响应规律。[结果](1)3个处理下杨树人工林树干液流年变化曲线呈现单峰型,与饱和蒸汽压差、光合有效辐射的年际变化曲线相似。树干液流速率在夏季达到峰值,接着随着时间推移逐渐下降,到达林木休眠期时液流密度趋近于0;(2)模拟干旱下,随着截流程度增大,树干液流随之降低。D_(1)和D_(2)生长季液流密度平均值比对照组显著下降了24%~39%(p<0.05);(3)混合效应模型表明饱和蒸汽压差和土壤温度与液流变化极显著相关(p<0.01),大气温度,降雨量和土壤温度与液流变化显著相关(p<0.05)。[结论]移除30%的穿透雨提高了各环境因子对液流变化的解释程度,即干旱条件下会提高树干液流对环境变化的敏感性,其中土壤含水量对液流变化的解释率最高。未来仍需继续探讨树木自身性状对环境的响应。

[Objective]The Objectives of this study are to estimate the effects of throughfall exclusion(drought)on the sap flow in a Populus deltoides plantations and to enhance our understanding of the response of poplar plantations to changes in global precipitation patterns.[Methods]The study was conducted from September 2018 to November 2020 in a 10-year old poplar plantation in Dongtai Forest Farm.There were three treatments in this study,including CK(control),D_(1)(30%throughfall exclusion),and D_(2)(50%throughfall exclusion).The sap flow density and environmental factors were continuously measured by thermal diffusion probe technology and the Micro Weather Monitoring System to evaluatethe response of the poplar plantation to environmental factors.[Results](1)In three treatments,the annual variation of sap flow in poplar plantations showed a single peak,similar to the interannual variation of vapor pressure deficit and photosynthetic active radiation.The sap flow rate reached its peak in summer,and then gradually decreased over time.In the dormant period,the sap flow density approached zero.(2)In the drought treatment,the sap flow decreased with the increasing throughfall exclusion.The average sap flow density in the growth seasons of D_(1)and D_(2)were 39.61 and 31.85 g/(m^(2)s),respectively,which were significantly reduced by 24%to 39%compared to the control(p<0.05).(3)The mixed effect model showed that the vapor pressure deficit and soil temperature were extremely significantly correlated with sap flow(p<0.01),while air temperature,rainfall,and soil temperature were significantly correlated with sap flow(p<0.05).[Conclusion]In D_(1)treatment,the power of explanation of environmental factors to sap flow increased,and the sensitivity sap flow to environmental changes could be increased in drought treatments.Among them,soil temperature was significantly correlated with sap flow.Further exploration of the response of tree traits to the environment is needed in the future.