热带桉树树干液流的时滞效应分析

目的]探明热带桉树树干液流与环境因子间的时滞效应及其影响因素.方法]运用Granier热扩散探针技术对海南省西北部儋州林场生长季(5-10月)桉树树干液流速率进行了实时监测,并同步监测了光合有效辐射(PAR)、大气温度(Ta)、相对湿度(Rh)和0～60 cm土壤含水率(SWC),运用错位相关法分析了液流速率与PA...

Sap Flow in the Stem of Eucalyptus and Changes in Meteorological Factors are not Consistent

【Objective】Water ascent in plants is driven by water vaporization from their leaves and mediated by meteorological factors. However, how plant species affect the time taken by water to flow from soil to leaves remains poorly understood. Taking Eucalyptus as an example, we measured the sap flow in its stem in response to temporal changes in environmental and meteorological factors.【Method】The experiment was conducted at the Danzhou Forest Farm in Hainan, China. We measured the sap flow in the stem of a six-year-old Eucalyptus tree continuously for 6 months, using the Granier-type thermal dissipation probe(TDP). In the meantime, we also measured the photosynthetically active radiation(PAR), vapor pressure deficit(VPD), soil water content from the depths of 0 to 60 cm. The delay or advance of the sap flow was analyzed by comparing its correlation with temporal changes in PAR and VPD.【Result】Diurnal sap flow showed double peaks; there was a depressed photosynthesis at midday. On typical sunny days, sap flow peaked ahead of PAR and VPD by 60 min. Partial correlation analysis showed positive correlations between sap flow and PAR and VPD, both at significant level(P<0.001). Sap flow in the growing season was ahead of PAR and VPD by 30 min and 50 min respectively. The impact of soil water content on the inconsistency between sap flow and meteorological factors was significant(P<0.05) but the significance varied. When soil water content was >15.42%, sap flow was ahead of PAR and VPD by 60 min and 30 min respectively, while when it was <10.45%, the associated time advance changed to 0 min and 60 min respectively.The diameter of the stem did not show significant influence on the inconsistency between sap flow and PAR/VPD.【Conclusion】Sap flow in the stems of Eucalyptus was ahead of the change in PAR and VPD and the difference was influenced by soil water content. This finding has an important implication for water and agronomic management.