Purpose
The quality and quantity of dissolved organic carbon (DOC) in the soil can be used as indicators of the effects of perturbations on soil C. We studied the effects of land use systems (native forest, grassland, and arable land) in both Alberta, in western Canada, and Heilongjiang, in northeast China, on the quality and quantity of soil DOC.
Materials and methods
We studied the UV absorption, humification index (HIX), and biodegradability of water-extractable organic C, which is operationally defined as DOC. The relationship between biodegradability and the structural chemistry of soil organic matter studied with 13C-nuclear magnetic resonance (NMR) spectroscopy was also investigated.
Results and discussion
The UV absorption and HIX, biodegradability of DOC, and the proportion of organic matter functional groups were not different among the land use types in both Canada and China. When the samples from both countries were considered together, the extractability of DOC was negatively correlated with soil organic carbon content and carbonyl C, and positively correlated with O-alkyl C; the biodegradability of DOC was positively correlated with soil C/N ratio, and negatively correlated with the specific UV absorbance and HIX.
Conclusions
The main effect of land use type on soil organic matter was on its content but not the labile C characteristics or organic matter functional group composition, indicating the dominant control of the climate on the quality of DOC of the organic matter under different land use types we studied in the two cold temperate regions.