Beaver Ponds and the Carbon Cycle

Carbon takes a variety of forms in beaver ponds and beaver meadows, including live plant biomass, standing dead biomass, soil organic matter, soil carbonates, dissolved organic carbon, and trace gases. The pools of carbon in these storage compartments and the fluxes between them are discussed. The slow decomposition rate of beaver meadow plant litter under anaerobic conditions promotes the accumulation of organic (O) soil horizons, which have a calculated mean residence time of 69 years. The carbon per unit area in soils that were formerly impounded by beavers (15.1 ± 6.8 km C m−2) was nearly twice that of adjacent never-impounded forest soils (8.2 ± 2.9 km C m−2). Beaver meadow sedge peat mineralization was compared with that of bog peat in long-term (80-week) laboratory incubations. Beaver meadow sedge peat had significantly higher carbon mineralization rates under all incubation conditions except aerobic incubation at 15 °C (other treatments were anaerobic incubation at 15 and 30 °C and aerobic incubation at 30 °C). Field measurement of trace gas fluxes showed that beaver ponds and beaver meadows with water table at or above the soil surface emitted methane, but beaver meadows with water tables below the soil surface did not.