Short-term physiological responses of Larix kaempferi seedlings to spring warming and drought manipulation

Abstract Excessively high temperatures and droughts after winter dormancy can affect the physiological responses of plant seedlings. In the present study, an open-field experiment was conducted to investigate the impact of spring warming and drought treatments on the short-term physiological responses of 1-year-old Larix kaempferi seedlings. The warming treatment was designed to increase the air temperature by 4 °C compared to that of the temperature control plots and was carried out for seven days each in the second and fourth week of May 2020. Moreover, the drought treatment was designed to completely block precipitation for four weeks in May 2020. After the first warming treatment period, stomatal conductance, transpiration rate, and net photosynthetic rate decreased by 35.16%, 29.53%, and 13.34% in the temperature warming plots compared to those in the temperature control plots, respectively. After the resting stage, stomatal conductance and transpiration rate increased by 101.47% and 72.80% in the temperature warming plots compared to those in the temperature control plots, respectively. Stomatal conductance, transpiration rate, and net photosynthetic rate tended to decrease in the drought treatment. The total chlorophyll content did not change under the warming treatment, but it increased by 20.29% in the drought treatment plots compared to that in the precipitation control plots in the fourth week; this may have resulted from chlorophyll hormesis. Furthermore, the correlation and principal component analyses showed that seedling physiological responses and environmental conditions were closely related. We found that spring warming and drought treatments can reduce stomatal conductance, transpiration rate, and net photosynthetic rate, thus affecting seedling growth. This study is expected to be the basis for more in-depth studies on the effects of warming and drought treatments on the growth and phenology of L. kaempferi seedlings.