缙云山典型树种树干液流径向变化及单株日蒸腾量估算

Radial Variations of Sap Flow Velocity for Typical Species in Jinyun Mountain and the Estimates of Single Tree's Daily Transpiration

为分析树干液流速率径向变化,准确估算单木蒸腾量,运用Granier热扩散探针方法于2015年7-9月对重庆缙云山自然保护区内2个典型树种（杉木、四川山矾）树干木质部3个深度（10mm,30mm,50mm）的液流速率（V）进行测定。结果表明：杉木树干液流速率径向分布规律为：V（30-50mm）〉V（10-30mm）〉V（0-10mm）,V（30-50mm）是V（0-10mm）的1.65倍,V（10-30mm）是V（0-10mm）的1.12倍。四川山矾树干液流速率径向分布规律为：V（10-30mm）〉V（0-10mm）≈V（30-50mm）,V（10-30mm）约为V（0-10mm）和V（30-50mm）的2.6倍;各深度处的液流速率之间呈显著线性相关关系;树干木质部不同深度处液流速率日变化规律呈单峰或双峰走势;7月份液流速率值最大,树木蒸腾出现＂午休＂现象;液流启动及到达峰值的时间在时间和空间上都存在差异。7月份液流启动时间和到达峰值时间早于8,9月份。径向上液流速率最大的位置,液流启动时间最早,到达峰值时间最晚;运用3个深度的液流速率分区域计算得到的杉木日蒸腾量为7 274.815g,四川山矾日蒸腾量为12 481.494g;忽略树干液流径向差异,以单一深度处液流速率估算日蒸腾量,对杉木产生的误差为10.29%-22.60%,变异系数CV为37%-60%,对四川山矾产生的误差为42.41%-66.88%,变异系数CV为19%-26%。

Using Granier-type thermal dissipation probes, sap flow velocity （V） of two species （Cunning- hamia lanceolata, Symplocas setchuensis） were monitored in three depths （10 ram, 30 mm, 50 mm） of xylem from July to September, 2015, at Jinyun Mountain of Chongqing to analyze the radial variations of V and estimate trees transpiration accurately. The results showed that the radial pattern of V for Cunninghamia lanceolata was ranked as V30-50 mm〉V10-30 mm〉V0-10 ram. V30-50 mm was 1. 65 times of V0-10 mm and V10-30 mmWaS 1. 12 times of V0-10 mm. The radial pattern of V for Symplocas setchuensis was ranked as V10-30 mm〉V0-10 mm≈V30-50 mm. V10-30 mm was about 2. 6 times of V0-10 mm and V30-50 mm. There were significant liner relationships between every two depths. The daily variations of V in three depths of xylem displayed unimodal or bimodal curves. The value of V was highest in July and the transpiration was stopped in noon. There were temporal and spatial differences in start time and peak time of sap flow, which was earlier in July than in August and September. The start time was earliest and the peak time was latest at the plot where V was maximal in radial xylem. The daily transpiration of Cunninghamia lanceolata and Syrnplocas setchuensis were 7 274. 815 g and 12 481.494 g, estimated by different V in different depths. The error by omitting radial variations in V were 10.29%-22.60% for Cunninghamia lanceolata and 42.41%-66.88% for Symplocas setchuensis, its coefficient of variation （CV） were 37%-60% and 19-26%.