Arable lands

An overview of carbon dioxide (CO₂) exchange and soil respiration measurements is given for representative Hungarian agroecosystems. We present results of long-term atmosphere/biosphere CO₂ exchange measurements carried out at the Hungarian tall tower site (Hegyhá tsál). Tall tower net ecosystem exchange (NEE) measurements provided consistent estimates of landscape-wide carbon dioxide dynamics. During 1997-2008, the region mostly behaved as a net CO₂ sink on annual scale. Year-round NEE was in the range of-352 ± 49 g C m^-2 year^-1 and 43 ± 9 g C m^-2 year^-1 (negative values indicate uptake). The measurements are representative to a mixture of arable lands with small contribution from other biome types. Effects of different soil tillage methods-applied in two long-term tillage experiments (Józsefmajor, Karcag) and in a peach orchard (Vác)-on soil CO ₂ emission are also introduced. Soil respiration rate highly depended on the depth of soil disturbance and on the date of the measurements; CO ₂ emissions measured immediately after tillage applications and during the vegetation period showed contradictory tendencies. Results obtained from a newly developed laboratory CO₂ emission measurement method indicated strong coherences between soil carbon dioxide fluxes and soil water potential values.