Species-specific growth and photosynthetic responses of first-year seedlings of four coniferous species to open-field experimental warming

Temperature increase due to climate change may affect the growth and physiological traits of trees. To cope with climate change, it is important to understand the responses of trees to these changes, as well as how these responses vary among species, functional groups, and biomes. In this study, we aimed to examine the species-specific growth and photosynthetic responses of first-year seedlings of 4 coniferous species to future temperature increase by conducting an open-field experimental warming study. The air temperature in the warmed plots was maintained at 3.02 degrees C higher than that in the control plots with an open-field experimental warming system. The seeds of Pinus densiflora, Pinus koraiensis, Abies holophylla, and Abies koreana were planted in 2012, and the effects on growth, biomass allocation, leaf area, net photosynthetic rate, and chlorophyll contents of first-year seedlings were measured. Compared to the other species, P. densiflora showed pronounced responses to warming after the growing period, including increase in root collar diameter (RCD) and seedling height respectively by 10% and 6%, total biomass by 45%, net photosynthetic rate by 61%, and total chlorophyll content by 45%. For P. koraiensis, RCD, seedling height, and total chlorophyll contents increased by 7%, 5%, and 20% in warmed plots, respectively. A. holophylla showed an increase in RCD by 7%, whereas A. koreana responded inconsistently to warming. Changes in the seedling height to diameter ratio, organ-specific biomass, leaf area, and specific leaf area were also species-dependent. In addition, altered growth throughout the observation period was due to acclimation and phenological change. This suggests that species-specific growth responses to warming are affected by altered net photosynthetic rate, chlorophyll contents, and leaf area. Species-specific responses of first-year seedlings of 4 coniferous species to warming and the relationship between growth and photosynthesis might be applied to estimate the growth and distribution of coniferous species after future temperature rises.