Soil organic carbon in different land use on Arenosols

Soil organic matter predicts the productivity and sustainability of ecosystems (Franzmeier et al., 1985; Lal, 2009). The aim of the study was to assess the stability of soil organic carbon (SOC) in Arenosols within three different arable land use: (1) continuous arable land; (2) abandoned for the 15 years arable land; and (3) 50 years ago afforested with Scots pine (Pinus sylvestris L.) or silver birch (Betula pendula Roth) arable land. In mineral topsoil there were determined: (1) total SOC; (2) water extractable organic carbon (OC); (3) OC in unprotected, physically and silt and clay protected organic matter (OM); and (4) carbon in the mass of soil microbiota. Although the highest concentrations of water extractable carbon and carbon in unprotected OM, mineral topsoil after the afforestation, especially with the birch, contained the highest concentrations of total SOC and carbon concentrations in silt and clay protected OM. Meanwhile, mean carbon concentrations in microbiota biomass were the lowest in pine plantations, the highest – in birch stands and the intermediate – in arable or abandoned arable land. The obtained data confirmed that according to the Kyoto Protocol the afforestation of arable land on nutrient-poor sandy soils in Lithuania could be relevant, with the focus on carbon sequestration.