Effects of elevated temperature and [CO2] on photosynthesis, leaf respiration, and biomass accumulation of Pinus taeda seedlings at a cool and a warm site within the species' current range

We examined the influence of elevated temperature (ambient +2 degrees C) and atmospheric CO2 concentration ([CO2]) (700 mu mol.mol(-1)), applied singly and in combination, on biomass accumulation and the temperature response of net photosynthesis (A(net)) and leaf respiration (R-d) of loblolly pine (Pinus taeda L.) seedlings grown simultaneously at a northern and a southern site within the species' range. We used this experimental approach to determine if the response to future climate conditions would differ between a warm and cool location within a species' range. Seedling biomass accumulation and the temperature responses of A(net) and R-d were measured throughout the growing season. Biomass accumulation was substantially greater at the warmer site compared with the cooler site regardless of treatment. At each site, biomass accumulation was greater in the elevated temperature treatment compared with the ambient treatment. There was substantial acclimation of R-d, but not A(net), to site and to temperature treatment at each site. Elevated [CO2] increased biomass accumulation and A(net) at both sites and in both temperature treatments. Our study provides an indication that future projected increases in [CO2] and air temperature of 700 mu mol.mol(-1) and +2 degrees C, respectively, are likely to increase loblolly pine growth in most, if not all, of its current range.