Changes in organic matter properties and carbon chemical stability in surface soils associated with changing vegetation communities in permafrost peatlands

The organic matter (OM) properties of peat soils play an important role in maintaining the stability of the peatland carbon pool and carbon cycling under environmental disturbances. The environmental disturbances not only directly affect the peatland carbon pool, but also cause changing of the vegetation community, which potentially has direct effects on the OM properties of peat soils, especially for permafrost peatlands. To reveal the changing in the OM properties due to the changes of the vegetation community, we collected 137 surface peat samples from different vegetation communities in permafrost peatlands located in the northern Great Khingan Mountains. And the OM properties were analyzed by Fourier Transform infrared spectroscopy (FTIR). Here, we found that the aromatic contents in the moss surface soil were 27.77 ± 1.38%, which was higher than the other three types of surface soils. And the humification degree indicated by the FTIR 1720/1050 ratio in moss and herb surface soils was around 0.36, considerably lower than that in the shrub and tree surface soils, which was around 0.40. Considering there is no significant difference in available nutrients among different vegetation communities, we speculate that the potential reason for the changing of vegetation communities was the difference in the water table due to differences in micro-geomorphology. For predicting the vegetation communities based on the OM properties, the most suitable solution was to divide the vegetation community into three groups (i.e., tree/shrub, herb, and moss), thereby increasing the predictive accuracy to more than 80%.