The effect of mineral composition on soil organic matter turnover in temperate forest soils

Abstract

PurposeThe aim of this work was to determine the characteristics of SOM decomposition under forest vegetation and to investigate the influence of soil mineralogy on SOM turnover.MethodsThirteen Hungarian forest topsoil samples amended with maize residues were incubated at 20 °C for 163 days. The CO2 evolved was measured and the fast and slow decomposition rate constants (k1 and k2, respectively) of SOM were quantified using a first-order two pools model. Linear regression analysis was applied between the quantity of total mineralized carbon (TMC), k1 and k2 values and the mineralogical parameters of the soils.ResultsThe illite (R2 = 0.797, p < 0.001) and non-swelling clay mineral (R2 = 0.767, p < 0.001) content and the dithionite–citrate–bicarbonate-extractable Al (AlDCB, R2 = 0.708, p < 0.001) and ammonium-oxalate-extractable Al concentration (AlOX, R2 = 0.627, p < 0.01) reduced the TMC to the greatest extent. The AlDCB (R2 = 0.681, p < 0.001), AlOX (R2 = 0.583, p < 0.01) and illite (R2 = 0.545, p < 0.01) contents had strong negative relationship with the k1 value. The k2 value was only affected by the non-swelling clay mineral (R2 = 0.467, p < 0.05) and illite (R2 = 0.574, p < 0.01) contents.ConclusionThese results confirm that the mineral composition of the soil, including the Al oxide, non-swelling clay mineral and illite contents, may significantly inhibit the decomposition of SOM, showing that illite minerals may provide binding surfaces for SOM over a longer timescale.