Effects of extraction conditions on topsoil dissolved organic carbon concentration of black soil.

Aiming to confirm the effects of extraction methods on the concentration of topsoil dissolved organic carbon (DOC) and select suitable conditions for extracting DOC of black soil, topsoil samples in the depth of 0-10cm collected from four land use types, including Dahurian larch plantation, natural grassland, arable land and natural secondary forest from black soil, were used by measuring the concentration of DOC extracted with different water-to-soil mass ratios, extractants and temperatures. Results showed that: 1) the concentration of DOC extracted from topsoil presented a positive linear relationship significant with water-to-soil mass ratio (R2 ranged in 0.82-0.98). The differences of DOC concentrations in topsoil of four land use types were significant (P 0.05) when the water-to-soil mass ratio was 40:1 with a peak value in the natural secondary forest, which was 1.16, 1郾88 and 1郾61 times of larch plantation, natural grassland and arable land, respectively. 2) The type of soil extractant also had influence on concentration of DOC in topsoil to some degree. DOC extracted with deionized water resulted in a higher concentration compared with other conditions. 3) The extraction concentration of DOC under four land use types did not show a significant regularity until the temperature increased to 70 益(P 0郾05). It can propose a relatively appropriate extraction procedure for DOC concentration from topsoil, and which can reflect its differences among the land use patterns of black soil: field鄄moist soil extracted with deionized water at a 40:1 water-to-soil mass ratio.