Plant Biomass And Production And CO2 Exchange In An Ombrotrophic Bog

  • Sites: CA-Mer
  • Moore, T. R., Bubier, J. L., Frolking, S. E., Lafleur, P. M., Roulet, N. T. (2002/02) Plant Biomass And Production And CO2 Exchange In An Ombrotrophic Bog, Journal Of Ecology, 90(1), 25-36.
  • Funding Agency: —

    1. Above-ground biomass was measured at bog hummock, bog hollow and poor-fen sites in Mer Bleue, a large, raised ombrotrophic bog near Ottawa, Ont., Canada. The average above-ground biomass was 587 g m−2 in the bog, composed mainly of shrubs and Sphagnum capitula. In the poor fen, the average biomass was 317 g m−2, comprising mainly sedges and herbs and Sphagnum capitula. Vascular plant above-ground biomass was greater where the water table was lower, with a similar but weaker relationship for Sphagnum capitula and vascular leaf biomass.
    2. Below-ground biomass averaged 2400 g m−2 at the bog hummock site, of which 300 g m−2was fine roots (< 2 mm diameter), compared with 1400 g m−2 in hollows (fine roots 450 g m−2) and 1200 g m−2 at the poor-fen site.
    3. Net Ecosystem Exchange (NEE) of CO2 was measured in chambers and used to derive ecosystem respiration and photosynthesis. Under high light flux (PAR of 1500 µmol m−2 s−1), NEE ranged across sites from 0.08 to 0.22 mg m−2 s−1 (a positive value indicates ecosystem uptake) in the spring and summer, but fell to –0.01 to –0.13 mg m−2 s−1 (i.e. a release of CO2) during a late-summer dry period.
    4. There was a general agreement between a combination of literature estimates of photosynthetic capacity for shrubs and mosses and measured biomass and summer-time CO2 uptake determined by the eddy covariance technique within a bog footprint (0.40 and 0.35–0.40 mg m−2 s−1, respectively).
    5. Gross photosynthesis was estimated to be about 530 g m−2 year−1, total respiration 460 g m−2 year−1, and export of DOC, DIC and CH4 10 g m−2 year−1, leaving an annual C sequestration rate of 60 g m−2 year−1. Root production and decomposition are important parts of the C budget of the bog. Root C production was estimated to be 161–176 g m−2 year−1, resulting in fractional turnover rates of 0.2 and 1 year−1 for total and fine roots, respectively.