Inter-Research
Climate Research

ABSTRACT: Stimulation of photosynthesis at higher CO₂ concentrations is repeatedly observed in short-term experiments at the single leaf level. We scaled up from leaf to globe by use of a model of half-degree spatial resolution (ca 50 ¥ 50 km) and came to the conclusion that the CO₂-induced increase in the total terrestrial net primary production (NPP) may be described by the same simple formula that has been frequently used over the last 2 decades: NPP(Ca) = NPP₀[1 + gln(Ca/C0)], where Ca is the atmospheric CO₂ concentration. We also concluded that NPP₀ can be set at 61.6 Pg C yr^-1 and g at 0.35 (for C0 = 340 ppmv) in this formula. Proceeding from aircraft measurements of CO₂ concentrations and the isotopic carbon ratio, we assumed that the turnover time of the biological cycle is 19.2 yr, and we estimated the sink induced by CO₂ fertilization to be 1.3 Pg C yr^-1 (averaged for the period 1980-90). It is worth mentioning, however, that the estimate of the turnover time is so sensitive to the average isotopic shift that occurs on air-plant exchange that one can hardly define a feasible confidence interval for it.

KEY WORDS: CO₂ fertilization · Biosphere model · Carbon sink

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Published in CR Vol. 19, No. 3 (2002) on January 16
Print ISSN: 0936-577X; Online ISSN: 1616-1572. Copyright © Inter-Research, Oldendorf/Luhe, 2002