Soil Greenhouse Gas Fluxes From Different Land-Use Types in Mediterranean Spain.

Mediterranean agroecosystems are composed of different land-use types, which are randomly distributed within the territory. Ecosystem carbon (C) and nitrogen (N) dynamics vary between land-use types resulting in different soil greenhouse gas fluxes (GHG). In this experiment we measured GHG (i.e., carbon dioxide, CO₂; nitrous oxide, N₂O; methane, CH₄) fluxes under four different land-use types in a typical Mediterranean agroecosystem located in NE Spain. Land-use types consisted in a no-tilled barley field (NT), a 60-yr old pine forest (FR) and an 8-yr old set-aside area with half surface cultivated (SC) and the other half undisturbed (SU). Each land-use type comprised an area of approximately 350 m². GHG fluxes were measured every 20 days during the 2011-2012 cropping season (December 2011-June 2012). Soil GHG samples were taken in static chambers and measured with gas chromatography. Likewise, soil temperature, soil water content, dissolved soil organic C and soil mineral N were also measured in the surface layer (0-5 cm) at each sampling point. Land use affected soil fluxes in the three GHG measured. Moreover, temporal differences in GHG fluxes over the cropping season were explained by changes in soil microclimatic conditions and soil N and C availability. This study demonstrates the importance of accounting for GHG fluxes under the different land-use types and managements found over the Mediterranean region since they play an important role in the contribution of the Mediterranean agroecosystems to global warming mitigation.