The effect of mineral composition on soil organic matter turnover in temperate forest soils
Dóra Zacháry, Tibor Filep, Gergely Jakab, Marianna Ringer, Réka Balázs, Tibor Németh, Zoltán Szalai
Abstract
Abstract Purpose The 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. Methods Thirteen Hungarian forest topsoil samples amended with maize residues were incubated at 20 °C for 163 days. The CO 2 evolved was measured and the fast and slow decomposition rate constants (k 1 and k 2 , 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), k 1 and k 2 values and the mineralogical parameters of the soils. Results The illite ( R 2 = 0.797, p < 0.001) and non-swelling clay mineral ( R 2 = 0.767, p < 0.001) content and the dithionite–citrate–bicarbonate-extractable Al (Al DCB , R 2 = 0.708, p < 0.001) and ammonium-oxalate-extractable Al concentration (Al OX , R 2 = 0.627, p < 0.01) reduced the TMC to the greatest extent. The Al DCB ( R 2 = 0.681, p < 0.001), Al OX (R 2 = 0.583, p < 0.01) and illite ( R 2 = 0.545, p < 0.01) contents had strong negative relationship with the k 1 value. The k 2 value was only affected by the non-swelling clay mineral ( R 2 = 0.467, p < 0.05) and illite ( R 2 = 0.574, p < 0.01) contents. Conclusion These 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.