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Soil respiration (R S , Soil CO 2 efflux) is the second largest carbon (C) flux in global terrestrial ecosystems, and thus, plays an important role in global and regional C cycling; moreover, it acts as a feedback mechanism between C cycling and global climate change. R S is highly responsive to temperature and moisture, factors that are closely related to climate warming and changes in precipitation regimes. Here, we examined the direct and interactive effects of climate change drivers on R S of Pinus densiflora Sieb. et Zucc. seedlings in a multifactor climate change experiment involving atmospheric temperature warming (+3 • C) and precipitation manipulations (−30% and +30%). Our results indicated that atmospheric temperature warming induced significant changes in R S (p < 0.05), enhancing R S by an average of 54.6% and 59.7% in the control and elevated precipitation plots, respectively, whereas atmospheric temperature warming reduced R S by 19.4% in plots subjected to lower rates of precipitation. However, the warming effect on R S was influenced by soil moisture. On the basis of these findings, we suggest that atmospheric temperature warming significantly influenced R S , but the warming effect on R S may be weakened by warming-induced soil drying in water-limited environments.

The aim of this study was to investigate the short-term effects of warming treatment and precipitation manipulation on the growth, photosynthetic rate, and chlorophyll content of Pinus densiflora seedlings based on a climate change scenario in Korea. Twoyear-old P. densiflora seedlings were planted in a nursery in April 2013. The air temperature of warmed plots (W) was set to increase by 3 °C compared to control plots (C) using an infrared heater in May 2013. The three precipitation manipulations consisted of decreased precipitation using transparent panels (-30%; P-), increased precipitation using pumps and drip irrigation (+30%; P +), and a control (0%; P 0). Root collar diameter and seedling height of P. densiflora were measured in April and October 2013. Net photosynthetic rate and total chlorophyll contents were measured from June to October 2013. Warming treatment increased the growth of root collar diameter, and the interaction effect of the warming treatment and precipitation manipulation on it was also significant. In contrast, no significant effects were found for the growth of seedling height. These results demonstrate that warming treatment might affect the growth of root collar diameter and seedling height differently. It was also found that WPtreatment decreased net photosynthetic rates. This pattern might be due to the soil moisture availability, as soil moisture content was lowest in the WPtreatment and net photosynthetic rate was elevated with increasing soil moisture content. Meanwhile, warming treatment increased the total chlorophyll content. The results suggest that chlorophyll synthesis was promoted by a temperature increase in the leaves. The current study, which simulated a climate change environment in an open field, provides important information for the prediction of the ecophysiological effects of changes in temperature and precipitation on P. densiflora seedlings in Korea.

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 firstyear 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 °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 speciesspecific 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.