Differences in Transpiration Characteristics among Eucalyptus Plantations of Three Species on the Leizhou Peninsula, Southern China

How much transpiration water consumption varies between eucalyptus species is unknown, making the suitability of a particular eucalyptus species for large-scale planting in a given area, or whether interspecific differences need to be taken into account for eucalyptus water consumption estimates, uncertain. Here, Eucalyptus camaldulensis Dehnh. (Ec), Eucalyptus pellita F. v. Muell. (Ep), the most resistant species, and Eucalyptus urophylla S.T. Blake x Eucalyptus grandis Hill ex Maiden (Eug), the most widely planted species, were monitored for sap flow. Their stand transpiration was also estimated and its relationship to various influencing factors analyzed for the same stand age and site, and predictive models for daily transpiration (T) developed. The results showed that the T of all eucalyptus species was jointly influenced by meteorological factors, soil water content (SWC), and leaf area index (LAI), with great variation in the T response to each influencing factor among species. Accordingly, we developed species-specific transpiration prediction models that could adequately explain the changed T of each species (R-2-values: 0.863-0.911). There were significant differences in the stand daily mean sap flow density (J(C)) and transpiration among the three species. Although Ec had a significantly lower J(C) than Ep, it was significantly higher than Eug on all timescales, where the mean annual J(C) of Ep (0.11 cm min(-1)) was 1.4 and 2.6 times that of Ec (0.08 cm min(-1)) and Eug (0.042 cm min(-1)), respectively. Transpiration of Eug was significantly less than Ep, but significantly greater than Ec on all timescales, where the annual transpiration of Ep (743.41 mm) was 2.4 and 1.5 times that of Ec (311.52 mm) and Eug (493.58 mm), respectively. These results suggest that interspecific differences cannot be ignored when estimating transpiration rates in Chinese eucalyptus plantations, whose amount of water use should be considered when choosing the most optimal species to plant regionally.