COS 143-2 - Diurnal gas exchange responses of Pinus densiflora seedlings to open-field short-term warming and drought treatments

Abstract: This study was conducted to investigate the diurnal gas exchange responses of Pinus densiflora seedlings to short-term warming and spring drought. In March 2022, 20 plots (2 temperature levels × 2 precipitation levels × 5 replicates) with a dimension of 1.5 m × 1.0 m were constructed in central Korea, and 28 3-year-old P. densiflora seedlings were planted in each plot. The temperature of the warming plots was set to increase by 4 °C compared to that of the temperature control plots from May 14th to August 9th. Precipitation of the drought plots was completely blocked from May 14th to June 15th using an automatic rainout shelter, while precipitation control plots experienced ambient precipitation. The diurnal gas exchange of seedlings was measured every month from May to October 2022. Photosynthetic rate, transpiration rate, and stomatal conductance of P. densiflora significantly decreased by short-term warming from a month later the treatment establishment and recovered promptly after the treatment cessation, showing 25.2%, 18.2%, and 18.7% reduction during June and 27.0%, 34.5%, and 35.7% reduction during July, respectively. Short-term drought induced a more immediate response to gas exchange, reducing photosynthetic rate, transpiration rate, and stomatal conductance by 32.4%, 27.5%, and 26.0%, respectively, in May and 40.3%, 44.9%, and 42.8%, respectively, in June. Gas exchange of the seedlings also recovered within a month after the cessation of the drought treatment. There was a significant correlation between the stomatal conductance response to warming and time of measurement in July, while all parameter responses of gas exchange to drought had a correlation with time of measurement in June. In July, short-term warming decreased stomatal conductance more severely at 12:00-15:00, showing a 42.6% reduction. The reduction in photosynthetic rate, transpiration rate, and stomatal conductance to drought were also significantly higher at 12:00-15:00, showing 57.0%, 56.3%, and 55.9% reduction, respectively. This study indicates that short-term warming and drought can cause short-term losses in plant gas exchange, and those losses could be higher during a hotter period of the day.



* This research was carried out with the support of R&D Program for Forest Science Technology (Project No. 2020181B10-2222-BB01) provided by Korea Forest Service (Korea Forestry Promotion Institute) and the Korea Forest Service Government (KFSG) as [Graduate School specialized in Carbon Sink].