In this paper, we present an investigation of interspecies differences in transpiration of the 2 most common plantation forest tree species in Japan, both in the family Cupressaceae with different northern limits of native distribution, Japanese cypress (Hinoki; Chamaecyparis obtusa Sieb. et Zucc.) and Japanese cedar (Sugi; Cryptomeria japonica D. Don). The stem sap flow rate was measured in 2 nearby stands of similar leaf area index in a 42-year-old plantation. Single-tree and stand-scale transpiration rates (Etre and Esta, respectively) were observed during an ideal autumn environment. At the stand scale, mean sap flux density of Hinoki was greater than that of Sugi, whereas total sapwood area per ground area was smaller in Hinoki than Sugi. Because the 2 variables had counterbalancing effects on transpiration, Esta of Hinoki was similar to (94% of) that of Sugi. This offset was also found between the mean Etre of the 2 species. Esta was similar between the stands from May to October, whereas Esta of Sugi was notably greater than that of Hinoki from February to April. During these 3 months, the difference in cumulative Esta was 21.7 mm, which accounted for 79% of the difference in annual Esta between Hinoki and Sugi (192 and 219 mm/year, respectively). We found that canopy conductance (Gc) and its sensitivity to the mean vapour pressure deficit during daylight hours in Sugi were particularly high in early spring, whereas those in Hinoki shifted gradually throughout the growing season. This difference was related to the optimal temperature of Gc in Sugi, which was approximately 10 °C lower than that in Hinoki. Our results suggest that plantations of water-conserving species such as Hinoki produce timber slowly but yield water resources generously. Moreover, for plantations of trees sensitive to high temperature, such as Sugi, managers should be concerned about possible future decline caused by anticipated global warming.
All Science Journal Classification (ASJC) codes
- Water Science and Technology