Changes in wood anatomical traits in Scots pine under different climate-change scenarios

Although cell-anatomical variables are promising proxies reflecting seasonal as well as annual climate changes, their interdependencies are not yet fully understood. In the present study we assessed the changes in tree-ring width and various wood anatomical traits, including wall thickness, lumen diameter and tracheid diameter in the radial direction in saplings of Pinus sylvestris under six climatic conditions: 5°C warmer alone (ET) or combined with drought in June (ETJ) and in August (ETA) and CO₂ enrichment alone (EC, 770 ppm) or combined with drought in June (ECJ) and in August (ECA). The experiments related to temperature conditions using 2-year saplings and CO₂ conditions using 3-year saplings were completed in 2009 and 2010 in a greenhouse, respectively. Results showed that tree-ring width and tracheid diameter were not affected by any of the conditions applied, but the lumen diameter was larger and the wall thickness was thinner than those under control conditions. These reactions were verified under ETJ in the warming treatment and under all conditions under CO₂ enrichment conditions. Our results indicated that drought counteracted the effects of elevated CO₂ concentrations on wood anatomical properties, signifying complex interactions between the two major effects of climate change. Our comparison of wood parameters through experiments highlight the potential effect of climate change — increased drought stress due to higher temperatures and water shortage as well as elevated ambient CO₂, on tracheid lumen diameter and wall thickness. Whereas the ring-width and tracheid diameter practically remained unaffected under the above-mentioned conditions.