Dissolved carbon leaching from soil is a crucial component of the net ecosystem carbon balance

Reimo Kindler (1) , Jan Siemens (2) , Klaus Kaiser (3) , David Christopher Walmsley (4) , Christian Bernhofer (5) , Nina Buchmann , Pierre Cellier , Werner Eugster (6) , Gerd Gleixner , Thomas Grünwald (5) , Alexander Heim (7) , Andreas Ibrom , Stephanie Jones , Mike Jones (8) , Katja Klumpp , Werner L Kutsch (9) , Klaus Steenberg Larsen , Simon Lehuger , Benjamin Loubet , Rebecca Mckenzie , Eddy Moors , Bruce Osborne (5) , Kim Pilegaard (10) , Corinna Rebmann , Matt Saunders (11) , Michael Schmidt (5) , Marion Schrumpf (12) , Janine Seyfferth , Ute M Skiba , Jean-Francois Soussana , Mark A. Sutton , Cindy Tefs , Bernhard Vowinckel (5) , Matthias Zeeman (5) , Martin Kaupenjohann

1 Chair of Waste Management and Environmental Research
2 INRES Bodenwissenschaften
3 Soil Sciences
4 UCD School of Biology & Environmental Science
5 Department of Hydrosciences [Dresden]
6 Institute of Plant-, Animal-, & Agroecosystem Sciences
7 Department of Geography
8 Botany
9 Institut für Agrarrelevante Klimaforschung
10 Biosystems Division [Roskilde]
11 School of Biology & Environmental Science
12 MPI-BGC - Max Planck Institute for Biogeochemistry

Estimates of carbon leaching losses from different land use systems are few and their contribution to the net ecosystem carbon balance is uncertain. We investigated leaching of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and dissolved methane (CH4), at five forests, four grasslands, and three croplands across Europe. Biogenic contributions to DIC were estimated by means of its δ13C signature. Leaching of DOC plus biogenic DIC was 11.9 ± 5.9 g C m-2 yr-1 for forests (median: 7.4 g C m-2 yr-1), 29.4 ± 8.0 for grasslands (median: 34.2 g C m-2 yr-1), and 18.3 ± 3.5 g C m-2 yr-1 for croplands (median: 17.8 g C m-2 yr-1). The average flux across land use systems was 19.4 ± 4.0 g C m-2 yr-1 (median: 15.2 g C m-2 yr-1). Production of DOC in topsoils was positively related to their C/N ratio and its retention in B horizons of subsoils was inversely related to the ratio of organic carbon to iron plus aluminium (hydr)oxides. Partial pressures of CO2 in soil air and soil pH determined DIC concentrations and fluxes, but soil solutions were often supersaturated with DIC in relation to soil air CO2. Leaching losses of biogenic carbon from grasslands equalled 5-98% (median: 22%) of net ecosystem exchange (NEE) plus carbon inputs with fertilization minus carbon removal with harvest. Carbon leaching increased the net losses from cropland soils by 24-105% (median: 25%). For the majority of forest sites, leaching hardly affected actual net ecosystem carbon balances because of the small solubility of CO2 in acidic forest soil solutions and large net ecosystem exchange. Leaching of CH4 proved to be insignificant compared with other fluxes of carbon or CO2-C equivalents. Overall, our results show that leaching losses are particularly important for the carbon balance of agricultural systems.

Mots clés: Life Sciences

Domaines: Milieux et Changements globaux

Reimo Kindler, Jan Siemens, Klaus Kaiser, David Christopher Walmsley, Christian Bernhofer, et al.. Dissolved carbon leaching from soil is a crucial component of the net ecosystem carbon balance. Global Change Biology, 2010, 17 (2), pp.1167. ⟨10.1111/j.1365-2486.2010.02282.x⟩. ⟨hal-00599523⟩