The European carbon balance. Part 4: integration of carbon and other trace‐gas fluxes

Abstract

Overviewing the European carbon (C), greenhouse gas (GHG), and non-GHG fluxes, gross primary productivity (GPP) is about 9.3 Pg yr-1, and fossil fuel imports are 1.6 Pg yr-1. GPP is about 1.25% of solar radiation, containing about 360 x 1018 J energy - five times the energy content of annual fossil fuel use. Net primary production (NPP) is 50%, terrestrial net biome productivity, NBP, 3%, and the net GHG balance, NGB, 0.3% of GPP. Human harvest uses 20% of NPP or 10% of GPP, or alternatively 1 parts per thousand of solar radiation after accounting for the inherent cost of agriculture and forestry, for production of pesticides and fertilizer, the return of organic fertilizer, and for the C equivalent cost of GHG emissions. C equivalents are defined on a global warming potential with a 100-year time horizon. The equivalent of about 2.4% of the mineral fertilizer input is emitted as N(2)O. Agricultural emissions to the atmosphere are about 40% of total methane, 60% of total NO-N, 70% of total N(2)O-N, and 95% of total NH(3)-N emissions of Europe. European soils are a net C sink (114 Tg yr-1), but considering the emissions of GHGs, soils are a source of about 26 Tg CO(2) C-equivalent yr-1. Forest, grassland and sediment C sinks are offset by GHG emissions from croplands, peatlands and inland waters. Non-GHGs (NH(3), NOx) interact significantly with the GHG and the C cycle through ammonium nitrate aerosols and dry deposition. Wet deposition of nitrogen (N) supports about 50% of forest timber growth. Land use change is regionally important. The absolute flux values total about 50 Tg C yr-1. Nevertheless, for the European trace-gas balance, land-use intensity is more important than land-use change. This study shows that emissions of GHGs and non-GHGs significantly distort the C cycle and eliminate apparent C sinks

North America's net terrestrial CO<sub>2</sub> exchange with the atmosphere 1990–2009

“…As summarized by , AIMs combine data from an observation network of atmospheric CO 2 concentrations with models of surface CO 2 flux and atmospheric transport to infer, from an inversion process, the net landatmosphere exchange of CO 2 -C. Because they provide an integrated estimate of all CO 2 sources and sinks (over a given land area and time period) from the atmospheric perspective, inversions are sometimes referred to as a top-down approach Schulze et al, 2009). In estimating net land-atmosphere exchange, the influence of fossil fuel emissions is assumed to be well-known, and their influence is removed from the problem prior to solving for non-fossil fluxes Schulze et al, 2010 et al (2013). North America here is defined by the combination of TransCom3 regions "North American Boreal" and "North American Temperate" (Fig.…”

Winter greenhouse gas fluxes (CO<sub>2</sub>, CH<sub>4</sub> and N<sub>2</sub>O) from a subalpine grassland

“…Measurement networks such as GHGEurope or FLUXNET deliver fundamental data to investigate biogeochemical processes at the ecosystem scale (Aubinet et al, 2000;Baldocchi et al, 2001). Much of the research to date has focused on the biosphere-atmosphere exchange of carbon dioxide (CO 2 ) and more recently also on methane (CH 4 ) and nitrous oxide (N 2 O) in most of the major global ecosystem types, including arctic ecosystems Schulze et al, 2010). In comparison, less focus has been paid to subalpine or alpine grasslands (Gilmanov et al, 2007;Soussana et al, 2007;Ammann et al, 2007), particularly during winter (Brooks et al, 1997;Gilmanov et al, 2004;Filippa et al, 2009;Liptzin et al, 2009;Merbold et al, 2012).…”

Measuring the biosphere-atmosphere exchange of total reactive nitrogen by eddy covariance

“…Furthermore, agricultural land is supposed to act as both sink and source for N r (e.g., Sutton et al, 2000;Flechard et al, 2010) and, therefore, plays a key role for the spatial abundance of N r in the atmospheric boundary layer. The high importance of the terrestrial biosphere as source and sink of GHG is nowadays widely recognised and corresponding research programs (e.g., GreenGrass, CarboEurope-IP, NitroEurope-IP) and flux monitoring networks (FLUXNET, ICOS) have been initiated (Baldocchi et al, 2001;Soussana et al, 2007;Skiba et al, 2009;Schulze et al, 2010). In order to understand and being able to model the GHG exchange of an investigated ecosystem, also adequate information on the nitrogen exchange is needed (e.g., Lamarque et al, 2005;.…”