BEAVER IMPOUNDMENTS IN TEMPERATE FORESTS AS SOURCES OF ATMOSPHERIC CO2

Beaver impoundments trap large amounts of organic matter, and reminera lization of the organic matter to CO2 could make them a significant so urce of atmospheric CO2. Measurements in two beaver impoundments in th e Adirondack Park of New York State indicated that: (i) during the ice -free season C02 emission averaged 197 mmol m-2 d-1; (ii) concentratio ns of dissolved inorganic carbon (DIC) in the water column were always >100 muM, reaching >1000 muM beneath ice cover and in midsummer; and (iii) the rate Of CO2 production sediment samples from beneath the wat er column could exceed 300 nunol m-2 d-1 in midsummer. The CO2 emitted from the impoundments to the atmosphere is supplied both by the sedim ents beneath the impoundment and by transport into the water column fr om the surrounding uplands. If beaver impoundments cover 3% of the lan dscape in north temperate forests then the magnitude of the presumed C O2 sink in this landscape would be reduced by 7% compared with estimat es based only on the terrestrial component