Temperature responses of growth and wood anatomy in European beech saplings grown in different carbon dioxide concentrations

This study investigated relationships between wood anatomical properties, growth, and mass allocation of well-watered beech saplings growing in different temperature and carbon dioxide (CO2) regimes. The study was conducted to test whether growth was enhanced by increasing temperature and CO2, as well as to determine whether the leaf area to stem cross-sectional area ratio, leaf mass ratio, and leaf area ratio declined with increasing temperature. The study also investigated the hypothesis that vessel member and size decreases with increasing temperature and CO2 as well as the hypothesis that wood parenchyma content declines with increasing temperature and increases in response to elevated CO2. The beech saplings were grown in 7-1 pots for 2.5 years in field-phytotron chambers supplied with ambient or elevated CO2. Temperatures in the chambers ranged in increments of 2 degrees C. Soil was not fertilized and soil water and air humidity were kept constant. Data were evaluated by regression analysis. Results of the study showed that stem diameter was significantly larger at increased temperatures. In addition, stems were taller, and leaf area and stem mass were greater. The allocation pattern was influenced by temperature, as leaf mass ratio and leaf area ratio decreased with increasing temperature. Elevated CO2 enhanced height growth by 8.8 per cent, and decreased coarse root mass and total mass by 10.3 per cent. The root/shoot ratio was decreased by 11.7 per cent. At final harvest, a synergistic interaction was observed between elevated CO2 and temperature yielded trees that were 3.2 per cent taller at -4 degrees C, and 12.7 per cent taller at 4 degrees C than trees grown in ambient CO2. After 2.5 seasons, the cross-sectional area of the oldest stem part was approximately 32 per cent greater in the 4 degree C treatment than the -4 degree C treatment. In the final year, approximately 67 per cent more leaf area per unit tree ring area was produced in the highest temperature regime compared with the lowest. It was concluded that temperature had a greater effect on growth than CO2. However, CO2 caused quantitative changes in wood anatomy. 42 refs., 2 tabs., 3 figs