Landscape‐scale carbon storage associated with beaver dams

Abstract

Beaver meadows form when beaver dams promote prolonged overbank flooding and floodplain retention of sediment and organic matter. Extensive beaver meadows form in broad, low‐gradient valley segments upstream from glacial terminal moraines. Surveyed sediment volume and total organic carbon content in beaver meadows on the eastern side of Rocky Mountain National Park are extrapolated to create a first‐order approximation of landscape‐scale carbon storage in these meadows relative to adjacent uplands. Differences in total organic carbon between abandoned and active beaver meadows suggest that valley‐bottom carbon storage has declined substantially as beaver have disappeared and meadows have dried. Relict beaver meadows represent ~8% of total carbon storage within the landscape, but the value was closer to 23% when beaver actively maintained wet meadows. These changes reflect the general magnitude of cumulative effects in heterotrophic respiration and organic matter oxidation associated with historical declines in beaver populations across the continent.

Sediment and nutrient storage in a beaver engineered wetland

“…This summary is supported by previous research and is commonly attributed to the same factors such as channel discontinuity and flow velocity reduction that result in sediment deposition and storage of associated nutrients (Naiman et al ., 1986; Devito et al ., 1989; Lizarralde et al ., 1996; Klotz, 2013). Wohl (2013) estimated that even relict beaver dam‐related storage can account for 8% of total carbon storage within the landscape and actively maintained beaver wetlands up to 23%.…”

“…Such findings, in addition to high within‐site storage values, suggest that even when agricultural source areas are depleted in carbon, beaver ponds can still play a role in enhancing carbon storage in the landscape. Therefore, beaver dams may recreate valley bottom wetlands, which would have historically been nutrient rich (Wohl, 2013). …”

Beavers affect carbon biogeochemistry: both short‐term and long‐term processes are involved

“…In mountainous headwater catchments, beaver meadows store the great majority of C along rivers. This C storage source cumulatively represents approximately 8% (relict) to 23% (active) of the estimated total landscape C storage (Wohl ). The estimated 23% of total landscape C storage within active beaver meadows agrees well with another estimate for total C storage in unconfined valley bottoms (25%), which included beaver meadows and old‐growth forest with substantial downed wood (Wohl et al.…”

“…Thus, restoration of beaver populations and beaver meadows is of critical importance in management strategies designed to enhance ecosystem services such as habitat provision and C sequestration (Pollock et al. 2007b, Wohl ). When beavers were removed, the C storage of wet beaver meadows was replaced by the alternative ‘steady state’ of relatively dry grasslands (Wolf et al.…”

“…), it can be transmitted downstream (Naiman , Cirmo & Driscoll ), it can settle down to the bottom sediments (Einola et al. , Wohl ), or it can be stored in beaver meadow vegetation and soil, creating long‐term C storage (Johnston , ).…”