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Journal Articles

Immediate and potential long-term effects of consecutive heat waves on the photosynthetic performance and water balance in Douglas-fir

Duarte, A. G.*; Katata, Genki; Hoshika, Yasutomo*; Hossain, M.*; Kreuzwieser, J.*; Arneth, A.*; Ruehr, N. K.*

Journal of Plant Physiology, 205, p.57 - 66, 2016/10

https://doi.org/10.1016/j.jplph.2016.08.012

Times Cited Count：33 Percentile：81.2(Plant Sciences)

The frequency and intensity of climatic extremes, such as heat waves, are predicted to increase globally, with severe implications for terrestrial carbon and water cycling. Temperatures may rise above critical thresholds that allow trees to function optimally, with unknown long-term consequences for forest ecosystems. In this context, we investigated how photosynthetic traits and the water balance in Douglasfir are affected by exposure to three heat waves. Photosynthetic carboxylation efficiency was mostly unaffected, but electron transport and photosynthetic rates under saturating light were strongly influenced by the heat waves, with lagging limitations on photosynthesis still being observed six weeks after the last heat wave. We also observed lingering heat-induced inhibitions on transpiration, minimum stomatal conductance, and nighttime stomatal conductance. Results from the stomatal models used to calculate minimum stomatal conductance were similar to gs-night and indicated changes in leaf morphology, such as stomatal occlusions and alterations in epicuticular wax. Our results show Douglas-fir's ability to restrict water loss following heat stress, but at the price of reduced photosynthetic performance. Such limitations indicate potential long-term restrictions that heat waves can impose on tree development and functioning under extreme climatic conditions.

Journal Articles

Ozone-induced stomatal sluggishness changes carbon and water balance of temperate deciduous forests

Hoshika, Yasutomo*; Katata, Genki; Deushi, Makoto*; Watanabe, Makoto*; Koike, Takayoshi*; Paoletti, E.*

Scientific Reports (Internet), 5, p.9871_1 - 9871_8, 2015/05

https://doi.org/10.1038/srep09871

Times Cited Count：84 Percentile：92.87(Multidisciplinary Sciences)

The phytotoxic nature of tropospheric ozone can impair forest productivity and affects stomatal functions. Although a delay in stomatal responses (ozone-induced stomatal sluggishness) to fluctuating stimuli has a potential to change carbon and water balance in forests, this effect is not included in the current models for ozone risk assessment to forest. Here we examined effects of ozone-induced stomatal sluggishness on carbon gain and transpiration of global deciduous forests by combining land surface model and global atmospheric chemistry model. Ozone-induced stomatal sluggishness enhances stomatal ozone uptake resulting in facilitating a decline of forest carbon acquisition and also enhancing transpiration. Our findings are consistent with previous experimental and field observational results, indicating that forest trees suffer significant impairment of carbon and water balance through ozone-induced stomatal sluggishness.

Oral presentation

Toward modeling of stomatal conductance under elevated ozone in forest trees

Hoshika, Yasutomo*; Watanabe, Makoto*; Katata, Genki; De Marco, A.*; Deushi, Makoto*; Carriero, G.*; Koike, Takayoshi*; Paoletti, E.*

no journal, ,

Ozone (O $_{3}$ ) enters leaves via stomata and causes a damage to leaves of trees. Modeling of stomatal conductance (g $_{s}$ ) is considered as an essential factor to assess O $_{3}$ impacts. In this presentation, our recent progress of research for the modeling of g $_{s}$ under elevated O $_{3}$ is summarized. First, we investigated g $_{s}$ parameters of the Jarvis-type model for forest tree types throughout the world. The optimal temperature of g $_{s}$ and g $_{s}$ response to predawn water potential changed according to the growth conditions. Next, an optimization model of stomata including O $_{3}$ effects was tested in free-air O $_{3}$ exposure experiment on Siebold's beech in Japan. The optimal stomatal model explained O $_{3}$ -induced stomatal closure in early summer. However, in late summer and autumn, the model did not explain the effects of O $_{3}$ on g $_{s}$ . This reflects the loss of closing response of stomata by O $_{3}$ (stomatal sluggishness) such as under low light conditions. Finally, we examined the effects of O $_{3}$ -induced stomatal sluggishness on carbon gain and transpiration of temperate deciduous forests in the Northern Hemisphere by combining a detailed multi-layer land surface model and a global atmospheric chemistry model. Our findings are consistent with previous experimental evidences, suggesting significant impairment of forest carbon and water balances attributed by O $_{3}$ -induced stomatal sluggishness.