Mineralisation and Changes in the Fractions of Soil Organic Matter in Soils of the Permafrost Region, Qinghai-Tibet Plateau, China

摘要

To determine the relationship between soil organic matter (SOM) decomposition and chemistry in the permafrost region of the Qinghai-Tibet Plateau (QTP), 300-day laboratory incubations at 25℃ and chemical fractionation were performed to characterise the mineralisation dynamics of organic carbon from soils under five vegetation conditions. The respiration rates in wet meadows were the highest, followed by the Kobresia pygmaea meadow and K. robusta meadow. After the incubation period, all four fractions of SOM - non-polarity soluble, water soluble, holocellulose and lignin contents - showed some decline, and the SOM decreased by 16-20 per cent in soils of the steppe, meadow and wet meadow. These results suggest that a large proportion of the organic matter in soils of the permafrost region in the QTP is mineralisable. Based on the changes in chemical fractions of organic matter, it could be determined that soils with higher water-soluble fractions had higher rates of carbon mineralisation, while the mechanisms involved in the respiration of different chemical fractions are complicated.