Carbon Greenhouse Gas Fluxes from Fenland Soils Under Intensive Agricultural Use Compared to Seminatural and Restoration Management.

Globally, peatlands represent a large carbon store in the global carbon cycle. In naturalconditions they are typically a sink for carbon but constitute a methane source. Today, largefractions of the fens in the midlatitudes are being used for intensive agriculture due to theirfertile organic soils. Conventional farming techniques require ongoing drainageleading to soil shrinkage and soil organic carbon loss via fluvial loss as well asdecomposition to carbon dioxide. The carbon source-sink relationships - measured by eddycovariance and closed chambers - of three fens in the Fenlands in East Anglia, UnitedKingdom were compared over a time period of three years; one fen is being used forintensive horticultural production supporting up to two harvests per year, a second is insemi-natural condition and a third is under restoration management for more than10 years. The fen under agricultural use showed a significant carbon loss year onyear (mean ≈750gCm-2yr-1) and the semi-natural fen was a small carbon sink,but also a small methane source. The fen under restoration management includingblocking of the drainage channels and re-seeding with wetland species was stilla small and consistent carbon source to the atmosphere (mean ≈110gCm-2yr-1)even 15 years after the end of agricultural use. Methane flux measurements in theseminatural and regenerating fen indicate relevant methane fluxes from ditches and smalltemporary water bodies. These results highlight the susceptibility of organic soilsto disturbance and carbon loss and the complexity of restoration strategies thatmay lead to renewed carbon storage after a period of intensive agricultural use. [ABSTRACT FROM AUTHOR]