油松和侧柏边材液流相对于空气温度的滞后效应

林木耗水的准确评价对于低耗水树种的选择及林分结构优化配置具有重要意义。利用热扩散式边材液流探针和自动气象站,对油松和侧柏的边材液流速率和空气温度等环境因子进行了为期一年的同步测定,分析了空气温度与边材液流间的滞后效应。研究结果表明:林冠上层空气温度与液流速率的相关性最为显著。液流启动要滞后于空气温度2h以上,液流峰值出现的时间一般要比空气温度早1～2 h,液流趋于停止的时间和空气温度相差不大。液流速率和空气温度之间存在明显的滞后效应,春、夏、秋季油松树干边材液流与空气温度变化的滞后时间分别为170 min、-60 min和0 min,侧柏边材液流相对于空气温度分别提前40 min、30 min和10 min。考虑液流相对于空气温度的"滞后效应"可提高液流速率的拟合精度,油松提高了42.9%～122.0%,侧柏提高了6.4%～14.6%。

Time Lag Effect of Pinus Tabulaeformis and Platycladus Orientalis Sap Flow Compared to Air Temperature

Accurate evaluation on forest water ansumption has great significance to tree species selection of low water consumption and stand structure configuration.The sap flow velocity of Pinus tabulaeformis and Platycladus orientalis,the air temperature and other environmental factors were synchronously measured in one year with thermal dissipation probes(TDP) and an automatic weather station.Time lag effect between sap flow velocity and air temperature was analyzed.Results showed that air temperature above the storey was most significantly correlated to sap flow velocity.Starting time of sap flow was generally 2 hours later than that of air temperature.Peak time of sap flow was somewhat earlier than that of air temperature.Stopping times were approximately at the same time.The time lag effect existed between sap flow velocity and air temperature.The lag times of Pinus tabulaeformis in spring,summer and autumn were about 170 min、-60 mim and 0 min respectively,while those of Platycladus orientalis were about 40 min、30 min and 10 min respectively.In conclusion,the model fitting precision would be improved with the lag effect during water consumption evaluation.The improved amplitude was 42.9%~ 122.0%in Pinus tabulaeformis and 6.4%~14.6%in Platycladus orientalis.