Premium
Carbon allocation in calcareous grassland under elevated CO 2 : a combined 13 C pulse‐labelling/soil physical fractionation study
Author(s) -
P. A. Niklaus,
E. Glöckler,
R. Siegwolf,
C. Körner
Publication year - 2001
Publication title -
functional ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.272
H-Index - 154
eISSN - 1365-2435
pISSN - 0269-8463
DOI - 10.1046/j.1365-2435.2001.00485.x
Subject(s) - growing season , grassland , biology , calcareous , fractionation , shoot , soil water , agronomy , soil carbon , zoology , botany , ecology , chemistry , organic chemistry
Summary1 To test whether plant–soil C fluxes in natural grassland increase under elevated atmospheric CO 2 concentration, intact calcareous grassland monoliths exposed to ambient or elevated CO 2 were pulse‐labelled and the dynamics of the 13 C label followed throughout the rest of the growing season. 2 The experiment revealed no increased fluxes of C to soils at elevated CO 2 . The only changes found were relatively small shifts towards increased C allocation to roots by the end of the growing season. This effect was probably because wetter soil under elevated CO 2 prolonged the growing period. At elevated CO 2 , plant C pools increased below ground (+28%) at the end of the season, resulting in slightly increased root : shoot ratios. Plant 13 C pools increased significantly below ground. There were no effects of CO 2 enrichment on 13 C in soil microbes, fine roots or earthworms. 3 Elevated CO 2 caused a shift in soil particle size distribution towards smaller aggregate sizes, but had no effect on the total C and 13 C content of low‐ and high‐density soil fractions. 4 The absence of effects of CO 2 on the labelling of soil microbial biomass, and of C and 13 C accumulation in low‐density macro‐organic fractions, suggest that there is no significant effect of elevated CO 2 on root exudation or turnover, agreeing with published labelling studies, but conflicting with CO 2 ‐exchange budgets.