Eddy covariance flux measurements of net ecosystem carbon dioxide exchange from a lowland peatland flux tower network in England and Wales
2016
Peatlands store disproportionately large amounts of soil carbon relative to other terrestrial ecosystems. Over recent
decades, the large amount of carbon stored as peat has proved vulnerable to a range of land use pressures as well
as the increasing impacts of climate change. In temperate Europe and elsewhere, large tracts of lowland peatland
have been drained and converted to agricultural land use. Such changes have resulted in widespread losses of
lowland peatland habitat, land subsidence across extensive areas and the transfer of historically accumulated soil
carbon to the atmosphere as carbon dioxide (CO2). More recently, there has been growth in activities aiming
to reduce these impacts through improved land management and peatland restoration. Despite a long history of
productive land use and management, the magnitude and controls on greenhouse gas emissions from lowland
peatland environments remain poorly quantified.
Here, results of surface-atmosphere measurements of net ecosystem CO2 exchange (NEE) from a network
of seven eddy covariance (EC) flux towers located at a range of lowland peatland ecosystems across the United
Kingdom (UK) are presented. This spatially-dense peatland flux tower network forms part of a wider observation
programme aiming to quantify carbon, water and greenhouse gas balances for lowland peatlands across the
UK. EC measurements totalling over seventeen site years were obtained at sites exhibiting large differences in
vegetation cover, hydrological functioning and land management.
The sites in the network show remarkable spatial and temporal variability in NEE. Across sites, annual
NEE ranged from a net sink of -194 ±38 g CO 2-C m-2 yr-1 to a net source of 784 ±70 g CO2-C m-2 yr-1. The
results suggest that semi-natural sites remain net sinks for atmospheric CO2. Sites that are drained for intensive
agricultural production range from a small net sink to the largest observed source for atmospheric CO2 within the
flux tower network. Extensively managed grassland and a site that was restored from intensive arable land use
represent modest CO2 sources. Temporal variations in CO2 fluxes at sites with permanent vegetation cover are
coupled to seasonal and interannual variations in weather conditions and phenology. The type of crop produced
and agricultural management drive large temporal differences in the CO2 fluxes of croplands on drained lowland peat soils. The main environmental controls on the spatial and temporal variations in CO2 exchange processes will be discussed.
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