Effect of sap flow radial variation on daily transpiration estimation of Eucalyptus urophylla × Eucalyptus grandis
The sap flow velocity of Eucalyptus urophylla × Eucalyptus grandis was measured at 0-2 cm and 2-4 cm sapwood depths using the Granier-type thermal dissipation probe (TDP) method to determine the effect of sap flow radial variation on whole-tree daily transpiration estimation,the estimation errors of different diameters at breast height (DBH),and the relationships between the estimation errors and photosynthetically active radiation (PAR) and vapor pressure deficit (VPD).Results showed that the daily transpiration of E.urophylla×E,grandis estimating with one point sap flow velocity at 0-2 cm was the highest,followed by the two points estimated value obtained from 0-2 cm and 2-4 cm,and that with one point sap flow velocity at 2-4 cm being the minimum.Compared to the two points estimated value,the sap flow velocity of 0-2 cm and 2-4 cm were overestimated by 32.9％ and underestimated by 58.7％,respectively.The estimation error with one-point sap flow velocity of 0-2 cm decreased along with the decreasing DBH.The estimation errors were 51.7％,33.0％ and 18.0％ at DBH 17.7,12.9 and 9.8 cm,respectively.The estimation error with the 2-4 cm sap flow velocity did not show significant difference among trees with different DBHs.There was a good positive correlation between estimation error and PAR and VPD when one-point sap flow velocity was used at 0-2 cm.Compared to the traditional method using only one point sap flow velocity,it was better to use multiple points estimate of sap flow velocity for a more accurate estimation of daily transpiration of E.urophylla × E.grandis.Our results provided a reliable estimate of water use in Eucalyptus plantation.
国家科技期刊平台
NSTL
万方数据
维普
