Effects of Open-field Warming and Precipitation Manipulation on the Growth of Pinus densiflora Seedlings

The objective of this study was to investigate the effects of open-field artificial warming and precipitation manipulation on Pinus densiflora seedling growth. The temperature in warming plots have been set to be 3°C higher than control plots using infrared lamps since April, 2013. Precipitation manipulation consisted of precipitation decrease plots (-30%) with deployment of rain-capturing transparent panels, precipitation increase plots (+30%) with pump installation and drip-irrigation, and control plots. Two-year-old P. densiflora seedlings were planted in April, 2013. Seedling height and root collar diameter were measured in April and November, 2013 and April, 2014, and biomass were measured in April, 2013 and April, 2014. During the period of April to November, 2013, increments of seedling height and root collar diameter were not significantly different between control and warming plots. However, in April, 2014 seedling heights, new shoot lengths and weights were higher in warming plots than in control plots, with all precipitation manipulation treatments (p<0.05). Shoot to root ratio was lower in warming plots than in control plots with the precipitation decrease treatment (p<0.05). The seedling height growth observed in 2013 and 2014 might be explained by the previous year's fixed growth of P. densiflora. Lower shoot to root ratio in warming plots with precipitation decrease treatment might be resulted from water stress. In previous studies about artificial warming and/or precipitation manipulation, the effects were increase, decrease or no difference in growth. As these results suggest, responses of growth are species-specific and/or are dependent on the stage of growth and the treatment types of climate change experiments. Therefore, to examine the effects of climate changes on plant growth, multi-factor and long-term studies on diverse species are needed.