Dynamique du carbone et de l'azote chez le Carex rostrata, l’Eriophorum vaginatum et le Calluna vulgaris dans une tourbière à sphaignes des monts du Forez (France)

Seasonal fluctuations in the biomass, necromass, and litter decay of Carex rostrata, Eriophorum vaginatum, and Calluna vulgaris were studied in the mire complex of Côte-de-Braveix, at 1350 m of altitude in the Forez Mountains of the eastern part of the Massif central (France). The primary production of these three dominant species of the main development stages of the studied peatland were respectively 456, 353, and 531 g ∙ m−2 ∙ a−1; the corresponding N fluxes were 4.5 g ∙ m−2 ∙ a−1 for the first two species and 5.2 g ∙ m−2 ∙ a−1 for the latter. The subterranean parts (rhizomes and roots) represented 66, 73 and 46% of the C production and 44, 47 and 37% of the N production, respectively. The biomass and N turnover rates were the highest in the E. vaginatum community (1.3 and 1.6) and the lowest in C. vulgaris (0.8 and 0.9); they were 1.1 and 1.2 in the C. rostrata community. The first year decomposition rate was equal to 0.30, 0.21 and 0.16 in the C. rostrata, E. vaginatum, and C. vulgaris litters. The production/accumulation ratio decreased from the fen to the bog species : 1.4 (C. rostrata), 1.3 (E. vaginatum), and 1.2 (C. vulgaris). The C and N balances are discussed from the viewpoint of ecological succession and peatland ecosystem development. Key words: fen, bog, primary production, decomposition, peat, succession.