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Above- and below-ground production of young Scots pine (Pinus sylvestris L.) trees after three years of growth in the field under elevated CO2

Jach, M.E., Laureysens, I., Ceulemans, R.
Annals of botany 2000 v.85 no.6 pp. 789-798
trees, dry matter partitioning, roots, field experimentation, seedlings, canopy, leaf area, branches, diameter, acclimation, carbon dioxide, chemical constituents of plants, plant litter, root shoot ratio, biomass production, Belgium
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 μ mol 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 CO2increased 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 CO2than in those grown in ambient CO2. Growth at elevated CO2caused 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 CO2took place mainly at the beginning of the experiment, when trees grown in elevated CO2had 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 CO2treatment were observed and are discussed.