Abnormal shoot responses of Pinus densiflora seedlings to open-field experimental warming and precipitation manipulation

This study was conducted to investigate the abnormal shoot responses of Pinus densiflora seedlings to open-field warming and precipitation manipulation. In May 2017, 18 plots (2 temperature levels × 3 precipitation levels × 3 replicates) of 1.0 m × 1.0 m were constructed in central Korea, and 90 1-year-old P. densiflora seedlings were planted in each plot. The temperature of the warming plots (TW) was set to increase by 3 °C compared to the temperature control plots (TC), and the precipitation was set to decrease (PD) and increase (PI) by 40% compared to the precipitation control plots (PC). The system was operated from June 2017. The occurrence rate of the number of seedlings showing abnormal shoot to the total number of seedlings was measured in September and November 2017, and abnormal shoot length was measured in November 2017. Seedling height was measured in May and September 2017, and the growth rate was calculated from the height difference between May and September 2017. The occurrence rate of abnormal shoot significantly increased by warming, but effects of precipitation and interaction between the two treatments were not significant. The mean occurrence rate of abnormal shoot observed in September and November were 86.2% and 90.8% in the TW and 58.8% and 64.8% in the TC, respectively. Abnormal shoot occurrence is known to be caused by the increase of growth period or high temperature under warming. However, high temperature is presumed to affect the increase of occurrence rate of abnormal shoot rather than the increase of growth period, since abnormal shoot occurred continuously until November in both TW and TC. The growth rate of seedling height significantly increased by warming. However, the abnormal shoot length did not show significant difference in both warming and precipitation manipulation. In this study, warming stimulated the growth of P. densiflora seedlings by promoting the occurrence of abnormal shoot rather than the increase in the growth of abnormal shoot length itself.

Acknowledge: This research was carried out with the support of Korea Forest Service (2017058A00-1819-AB01).