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利用树干液流方法获取树木蒸腾特征对理解树木水分生理、森林生态和森林系统水分交换具有重要意义.利用广泛应用于土壤热参数和土壤蒸发测量的三针热脉冲探头,基于热比率法(HRM)、最大温度法(T-Max)和单针热脉冲法(SHPP)同时实现了旱柳液流密度的测定,并与热扩散探针(TDP)测量结果进行对比分析.结果表明:三针热脉冲探头安装约5周后进入稳定测量阶段,3种方法初期测量结果比稳定测量阶段高135%~220%,HRM、T-Max和SHPP法与TDP测量结果具有显著的线性相关性,R2分别为0.93、0.73和0.91,SHPP与HRM法测定结果的R2达到0.94.HRM在低速和逆向液流时测量具有较高的精度;SHPP探头配置简单、测量精度高,但无法甄别液流方向,是测定液流非常有前途的方法;T-Max测量液流误差较大,无法测量<5 cm3·cm-2·h-1的液流,不建议单独用于液流测量,但其能够准确测定树干热扩散系数,并可用于其他方法液流计算.建议根据试验目的,选取不同方法或者几种方法组合进行树干液流测量.
It is of great importance to understand the transpiration of tree water by using the trunk flow method to understand the water physiology, forest ecology and forest system water exchange. Based on the three-pin thermal pulse probe widely used in soil thermal parameters and soil evaporation measurement, ), The maximum temperature method (T-Max) and the single-needle heat pulse method (SHPP) were used to determine the flow density of Salix matsudana at the same time, and the results were compared with the results of thermal diffusion probe (TDP) The thermal pulse probe entered the stable measurement stage after about 5 weeks of installation. The initial measurement results of the three methods were 135% ~ 220% higher than those of the stable measurement phase. HRM, T-Max and SHPP methods had significant linear correlation with TDP measurement results. R2 Respectively, 0.93, 0.73 and 0.91, respectively. The results of SHPP and HRM showed that R2 reached 0.94.HRM had higher accuracy when measured at low speed and reverse flow rate. SHPP probe was simple in configuration and high in accuracy but could not discriminate flow direction, Is a very promising method for measuring flow. T-Max has a large flow error and can not measure a flow of <5 cm3 · cm-2 · h-1. It is not recommended for flow measurement alone, but accurate The trunk thermal diffusivity is measured and can be used He flow calculation method recommended according to the test object, or a combination of several different methods of selection methods sap flow measurements.