Arable lands

Summary, in English

Three different, state-of-the-art biogeochemical models are adapted in order to quantify the carbon dioxide (CO₂), nitrous oxide (N ₂O), and methane (CH₄) exchanges between arable lands and the atmosphere. Biome-BGC and MOD17 are validated using the long-term measurement results from Hegyhátsál tall tower site (Western Hungary). After a simple bias correction, it was found that Biome-BGC is capable to describe the net ecosystem exchange (NEE) of Hungarian arable lands. The model is used to estimate the net primary production (NPP) and the net biome production (NBP) in the vicinity of the tall tower for the period of 1997-2008. The validation of MOD17 shows that the model is suitable to describe the gross primary production (GPP) of arable lands, although the model has limitations in years with higher precipitation amount. Introducing a new method MOD17 is downscaled to 250 m resolution, which is close to the size of agricultural parcels in the region. The downscaling helps us to better understand the biogeochemical processes of individual parcels with different crop cultivars. The DNDC model is parameterized using country-specific fertilizer input and climate data to provide estimates of the N₂O and CH₄ emissions for different crop cultivars. Sensitivity analysis was performed to find the most important parameters needed for accurate emission estimation. The results show that N₂O emission is highly variable for the different crop types, and it has significant contribution to the GHG balance of arable lands. Methane has bidirectional fluxes and arable lands were generally net sinks of CH₄ in the study period (2002-2004).