亚热带季风区樟树树干液流对降水的响应
夏银华1, 章新平1,2, 戴军杰1, 王 锐1, 罗紫东1

(1.湖南师范大学 地理科学学院, 长沙 410081; 2.湖南师范大学 地理空间大数据挖掘与应用湖南省重点实验室, 长沙 410081)

树干液流; 热扩散式探针技术; 降水; 土壤含水量; 蒸腾变量

Response of Stem Sap Flow of Cinnamomum Camphora to Precipitation Under Different Environments in the Subtropical Monsoon Region
XIA Yinhua1, ZHANG Xinping1,2, DAI Junjie1, WANG Rui1, LUO Zidong1

(1.College of Geographical Sciences, Hunan Normal University, Changsha 410081, China; 2.Key Laboratory of Geospatial Big Data Mining and Applicaion, Hunan Normal University, Changsha 410081, China)

stem sap flow; thermal dissipation probe; precipitation; soil moisture content; variable transpiration

备注

为探究樟树(Cinnamomum camphora)树干液流对降水的响应,利用热扩散式探针技术(TDP)于2019年6月—2020年5月在长沙地区连续观测了樟树树干液流,且同步测定了土壤含水量和气象因子,分析了樟树树干液流在不同天气条件下的日变化特征、不同量级降水条件下的特征以及不同土壤水分条件下对环境因子的响应。结果表明:(1)樟树树干液流随天气的变化而变化,晴天高于雨天。晴天液流日变化呈倒“U”型单峰曲线,雨天液流随降水的分布呈单峰、多峰曲线或一直处于较低值。晴天气象因子对液流的解释程度比雨天高。(2)液流对不同降水量的响应不同,0～5 mm降水前后液流差异性不显著; 大于5 mm降水后液流较降水前显著提高,但液流增幅与降水量之间没有明显的规律。5～10 mm,10～25 mm,25～50 mm和大于50 mm降水后液流增幅分别为13.2%,47.3%,20.6%和5.5%。(3)液流在少雨的土壤水分相对亏缺时期(RDP)较多雨的土壤水分相对充足时期(RSP)低,两个时期的液流与气象因子呈二次函数关系。不同土壤水分条件下液流与蒸腾变量的关系可以采用指数饱和函数进行拟合。RDP时期樟树的蒸腾作用受到抑制,降水后RSP时期土壤水分条件改善,樟树对太阳辐射、温度、饱和水汽压差和相对湿度的敏感性增加,导水能力增强。研究发现,树干液流对降水的响应因降水量的不同表现出较大的差异性,存在一定的降水阈值使降水后液流上升。降水可以通过引起气象因子的改变以及土壤水分的改善从而使樟树树干液流的水平提高。
In order to explore rainfall effects on sap flow of Cinnamomum camphora, thermal dissipation probe(TDP)was used to measure the stem sap flow of sample trees in Changsha from June 2019 to May 2020. Moreover the soil moisture content and meteorological factors were observed simultaneously. This study analyzed the diurnal variation characteristics of the stem sap flow under different weather conditions and its response to precipitation in different intensities. What's more, the response of sap flow to environmental factors under different soil moisture conditions had also been investigated. The results show that:(1)the sap flow changed with the weather, and it was higher on sunny days than on rainy days; daily variations of sap flow exhibited invented ‘U' mono-peak patterns during sunny days and showed single-peak or multi-peak curves or were always at a low level with the distribution of precipitation during rainy days; weather factors on sunny days could explain sap flow better than on rainy days;(2)precipitation with different intensities exerted different impacts on sap flow; sap flow was little change after 0～5 mm precipitation, whereas the sap flow increased significantly while the precipitation was more than 5 mm; however, there was no obvious regularity between the increase of sap flow and precipitation intensity; the sap flow after precipitation with 5～10 mm, 10～25 mm, 25～50 mm and greater than 50 mm increased by 13.2%, 47.3%, 20.6% and 5.5%, respectively;(3)the sap flow in the relative deficient period of soil moisture(RDP)and lack of rain was lower than that in the relative sufficient period of soil moisture(RSP)and plenty of precipitation; the sap flow in the two periods showed a quadratic function relation with meteorological factors; the relationship between liquid flow and variable transpiration under different soil water conditions could be fitted by the exponential saturation function; it was found that the transpiration of C. camphora was inhibited in RDP, and the sensitivity of transpiration reacting to solar radiation, temperature, saturated vapor pressure difference and relative humidity improved in RSP; moreover, the conductivity of the stem was enhanced too. In this study, the response of the stem sap flow to precipitation showed great difference due to the different precipitation, and there was a certain precipitation threshold that made the sap flow rise after precipitation. Precipitation can increase the sap flow level of C. camphora by changing meteorological factors and improving soil moisture.