Effects of lime and ash treatments on DOC fractions and low molecular weight organic acids in soil solutions of acidified podzolic soils

Abstract

Dissolved organic carbon (DOC) fractions and different low molecular weight organic acids (LMWOAs) were determined in soil solutions from two lime or ash treated Norway spruce sites in the south of Sweden. At Hasslov, 3.45 t ha-1 or 8.75 t ha-1 dolomite were applied 15 years before sampling. Horrod was treated with 4.28 t ha-1 ash and 3.25 t ha-1 dolomite and sampled four years later. Propionate (7–268 μM) and malonate (2–34 μM) were the LMWOAsfound in the highest concentrations at Hasslov. Two other LMWOAs dominated at Horrod, namely citrate (18–64 μM)and fumarate (5–31 μM). The differences in concentration of most of the determined LMWOAs at Hasslov were significantly increased due to treatment. The LMWOAs comprised between 1.1–6.3% of the DOC at Hasslov and 4.5–17.6% at Horrod. At Hasslov normally 3–10% of the total acidity (TA) was due to LMWOAs and the average specific buffer capacity was 74 ± 22 mmol mol-1C.The total DOC concentration in the mor layer solution was ∼16 mM for the dolomite treated plots compared to ∼10 mM at the untreated plot. A major part of the increase in DOC at the treated plots apparently had a hydrophobic character and was of high molecular weight corresponding to 3–10 kDa. The concentration of DOC < 1 kDa in the control and treated plots was similar.