Above- and Below-ground Production of Young Scots Pine (Pinus sylvestris L.) Trees after Three Years of Growth in the Field under Elevated CO

• Published in: Annals of botany Vol. 85; no. 6; pp. 789 - 798
• Main Authors: JACH, M. E., LAUREYSENS, I., CEULEMANS, R.
• Format: Journal Article
• Language: English
• Published: Academic Press 01.06.2000
• Subjects: Atmospherics; Biomass production; Branches; Nitrogen; Pine trees; Plant growth; Plant roots; Plants; Tree growth; Trees
• ISSN: 0305-7364; 1095-8290

Scots pine (Pinus sylvestris L.) seedlings were grown for 3 years in the ground in open top chambers and exposed to two concentrations of atmospheric CO₂ (ambient or ambient + 400 ₂mol mol⁻¹) without addition of nutrients and water. Biomass production (above-ground and below-ground) and allocation, as well as canopy structure and tissue nitrogen concentrations and contents, were examined by destructive harvest after 3 years. Elevated CO₂ increased total biomass production by 55%, reduced needle area and needle mass as indicated, respectively, by lower leaf area ratio and leaf mass ratio. A relatively smaller total needle area was produced in relation to fine roots under elevated CO₂. The proportion of dry matter in roots was increased by elevated CO₂, as indicated by increased root-to-shoot ratio and root mass ratio. Within the root system, there was a significant shift in the allocation towards fine roots. Root litter constituted a much higher fraction of fine roots in trees grown in the elevated CO₂ than in those grown in ambient CO₂. Growth at elevated CO₂ caused a significant decline in nitrogen concentration only in the needles, while nitrogen content significantly increased in branches and fine roots (with diameter less than 1 mm). There were no changes in crown structure (branch number and needle area distribution). Based upon measurements of growth made throughout the 3 years, the greatest increase in biomass under elevated CO₂ took place mainly at the beginning of the experiment, when trees grown in elevated CO₂ had higher relative growth rates than those grown under ambient CO₂; these differences disappeared with time. Symptoms of acclimation of trees to growth in the elevated CO₂ treatment were observed and are discussed.