Whole-seedling biomass allocation, leaf area, and tissue chemistry for Douglas-fir exposed to elevated CO2 and temperature for 4 years

Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were grown under ambient or elevated (ambient + 180 mumol.mol(-1)) CO2 and ambient or elevated (ambient + 3.5degreesC) temperature in outdoor, sunlit chambers with a field soil. After 4 years, seedlings were harvested and measured for leaf area, leaf, fine root (<1 mm diameter), and structural (buds, branches, stems, main root, and lateral roots >1 mm in diameter) dry masses, and leaf and fine root C/N ratio, percent sugar, and percent cellulose. Elevated CO2 did not affect biomass production or allocation for any plant organ but increased specific leaf mass, leaf C/N ratio, and percent sugar and decreased the ratio of leaf area to structural weight and leaf percent cellulose. Elevated temperature tended to reduce biomass allocation to leaves and leaf sugar concentration. Fine root percent sugar tended to increase with elevated temperature but only at elevated CO2. Therefore, for Douglas-fir seedlings growing under naturally limiting soil moisture and nutrition conditions, elevated CO2 and temperature may have little impact on biomass or leaf area except for reduced specific leaf mass with elevated CO2 and reduced biomass allocation to leaves with elevated temperature. However, both elevated CO2 and temperature may alter leaf chemistry.