雷州半岛尾叶桉人工林树液茎流特征的研究

Characteristics of Sap Flow in Eucalyptus urophylla Plantations on the Leizhou Peninsula

应用热脉冲法对雷州半岛4年生尾叶桉单株树干液流时空的动态变化及与各环境因子的关系进行观测研究。研究结果表明:(1)形成层以内木质部不同深度的茎流密度不同,其中靠近形成层部分液流速度较快,但各层都具有相同的日变化趋势,中午12点至1点达到最大;夜间因根压作用影响各层仍有微弱上升液流;各深度日平均茎流密度11 6L·m-2·d-1,最大为15 3L·m-2·d-1(晴天),最小仅为5 4L·m-2·d-1(雨天);(2)不同直径尾叶桉的日茎流密度具有相似日变化趋势,胸径与高度相近其茎流密度相同,大树较小树快,这主要与树木根系吸收土壤水分的能力有关;(3)热脉冲法与整树容器法对2年生幼树耗水量的同步测定结果相一致,误差仅为3 4%;(4)树干茎流量与饱和蒸气压差和太阳辐射相关性特别显著。

Heat pulse method was applied to study sap flux density (SFD) of single tree in 4-year-old Eucalyptus urophylla plantation from September 1999 to September 2000 on Leizhou Peninsula, southern China. The results indicated that SFD of outer sapwood moved faster than the inner; the daily SFD of trees with different diameter followed similar pattern, the bigger trees had faster SFD than smaller trees due to size of root system. To prove the accuracy of heat pulse method, water use of a 2-year-old young tree with height of 6 m was measured by the heat pulse method and a cut-stem method at the same time.It was showed that the estimated water use differed by 3.4% only. Among meteorological factors, solar radiation and VPD were the main factors affecting the sap flow. The heat pulse method was proved to be a accurate way to measure water transpiration by eucalypt tree plantations and recommended for wider application in water balance studies of plantations.