河南洛阳马尾松树干液流昼夜变化特征及其影响因子分析

Analysis on diurnal variation of sap flow in Pinus massoniana and its influencing factors in Luoyang, Henan Province, China

【目的】揭示马尾松(Pinus massoniana)在我国分布北界的树干液流昼夜特征及其与环境因子的关系,探索马尾松蒸腾耗水规律,为深入了解树木水分利用机制提供研究基础。【方法】以分布在河南洛阳的马尾松为研究对象,采用TDP热扩散探针和小型自动气象站对样地内的马尾松树干液流及周围环境因子进行连续监测,分析马尾松树干液流昼夜变化特征及其影响因子。【结果】(1)研究区马尾松树干液流速率呈昼高夜低的单峰曲线;马尾松存在夜间液流,零点前液流活动较零点后活跃。(2)6—10月的白天(太阳辐射大于5 W/m^(2))和夜间(太阳辐射小于5 W/m^(2))马尾松单株日均液流量为36.08 kg;夜均液流量为2.55 kg,占全天液流量的4.87%~9.27%;零点前液流量占夜间液流量的83.42%~95.54%。(3)马尾松树干液流速率与太阳辐射、饱和水汽压差(VPD)、温度、湿度、风速和降水量存在显著的相关性(P<0.05);太阳辐射是白天树干液流的最大影响因子,VPD是夜间树干液流的最大影响因子。【结论】在我国中西部地区相对干旱生境下,马尾松树干液流具有明显的昼夜变化规律;太阳辐射和VPD是研究区马尾松树干液流昼夜变化的主要影响因子;在估算马尾松液流量时,应充分考虑夜间液流的影响。

【Objective】The aims of this study are to understand the daily sap flow dynamics and the transpiration water consumption pattern of Pinus massoniana distributed in the northern boundary of China. The results from this study could provide a scientific basis for understanding of tree water use mechanisms. 【Method】 From June to October 2019, thermal diffusion probes(TDP) and automatic weather stations were used to monitor the trunk sap flow of P. massoniana and the surrounding environmental factors, respectively. This monitoring was conducted on the campus of Henan University of Science and Technology. 【Result】(1) The sap flow rate of P. massoniana in the study area showed a single peak curve, which was higher in the day and lower in the night. The P. massoniana had nighttime sap flow, and the sap flow was more active before 0:00 than after 0:00.(2) From June to October, the average daily whole tree sap flow of P. massoniana was 36.08 kg, the average nighttime whole tree sap flow was 2.55 kg;The nighttime sap flow accounted for 4.87%-9.27% of the daily total sap flow, and the sap flow before midnight accounted for 83.42%-95.54% of the nighttime total sap flow.(3) The sap flow rate had a linear relationship with solar radiation, vapor pressure deficit(VPD), temperature, humidity, wind speed and precipitation(P < 0.05);solar radiation and VPD were the main factors affecting sap flow during the daytime and nighttime, respectively. 【Conclusion】 In relatively drier habitats of the central and western regions in China, the sap flow of P. massoniana showed an obvious diurnal variation pattern. Solar radiation and VPD were the main factors influencing the diurnal stem sap flow of P. massoniana in the research area. At the same time, the effect of nighttime sap flow on the transpiration water consumption of individual trees should be considered in the transpiration calculation.