Humid climate may ameliorate negative effects of warming on growth and water use in Japanese boreal conifers
Assigned Session: FS 3.206: The Future of Mountain Forests
Abstract ID: 3.11613 | Not reviewed | Requested as: Poster | TBA | TBA
Haruhiko Taneda (1)
Yoshiyuki, Miyazawa (2); Susumu, Goto (3)
(1) The University of Tokyo, 1842 Hanaishicho, 321-1435 Nikko, JP
(2) Kyushu University, 74 Motooka, 819-0395, Fukuoka, Fukuoka, JP
(3) The University of Tokyo, 1-1-1 Midoricho, 188-0002, Tanashi, Tokyo, JP
Abstract
Previous studies indicated that boreal and mountainous evergreen conifers are vulnerable to increased temperatures due to global warming, resulting in reduced growth and survival rates, but some reports showed that those of the conifers in the regions where oceanic climate influence rather improve. However, these effects of oceanic climate may be species-specific and the physiological mechanisms remain unclear. To assess the ecophysiological details of boreal conifer growth at warm climate, we conducted two transplant experiments using three Japanese boreal conifers, Abies sachalinensis, Picea jezoensis, and Picea glauca. Saplings of these species were planted at three sites: Furano, near their native habitat; Chichibu, a warm inland region; and Chiba, a warm coastal region. In Experiment 1, we measured relative growth rates and survival rates. In Experiment 2, five years after Experiment 1, we measured photosynthesis and stomatal behavior in A. sachalinensis at the three sites. Results from Experiment 1 showed that high mortality of P. jezoensis and red P. glauca were found at the two warmer sites particularly at Chichibu. Relative growth rates (RGR) were the lowest at Chichibu in 2018 when severely hot summer was recorded, while the RGR at Chiba was similar with those at Furano. Notably, the d13C was significantly higher at Chichibu, suggesting that stomatal closure might cause a reduction in their growth. From Experiment 2, we found that three-year growth was higher in the order of Chiba, Furano, and Chichibu. Foliage mass for the last three years was smaller in Chichibu and Chiba trees than in Furano trees but their maximum photosynthetic rate did not differ. Onset of stomatal closure was detected at ~1.0 of VPD and ~-1.0 MPa of leaf water potential at both the individual leaf and branch levels, and these trends did not differ among trees grown at the three sites. Considering the large difference in air humidity in the three sites, we concluded that the boreal conifer growth at warmer sites was strongly influenced by stomatal closure due to high VPD, and high air humidity under the oceanic climate allowed the trees to maintain high stomatal conductance during growing seasons.
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