Aims: This paper focuses on quantifying the distribution patterns of plant communities along the permafrost thaw depth gradient, in order to develop a framework for predicting the response of vegetation characteristics in cold high latitude ecosystems to permafrost degradation as a result of climate warming. Study area: Great Hing'an Mountains of northeastern China. Methods: Thirty plots were selected in a west slope region of the Great Hing'an Mountain Valleys to study the relationship between the depth of the active layer of permafrost and characteristics of plant communities. Results: The distribution of plant communities strongly correlated with the permafrost thaw depth. With increasing depth of the active layer, important species showed an obvious transition and plant strategies shifted gradually from helophilous to hygrophilous to mesophilous. Both biodiversity and the total biomass of understory vegetation decreased significantly along this gradient. Conclusions: The response of the vegetation characteristics varied considerably with the depth of the active layer throughout the permafrost degradation. Our results show implications for vegetation in the face of climate change as rising temperatures directly affect permafrost, and in many areas the depth of the active layer is increasing.

Boreal peatlands represent a large global carbon pool. The relationships between carbon mineralization, soil temperature and moisture in the permafrost peatlands of the Great Hing'an Mountains, China, were examined. The CO2 emissions were measured during laboratory incubations of samples from four sites under different temperatures (5, 10, 15, and 20 degrees C) and moisture contents (0%, 30%, 60%, 100% water holding capacity (WHC) and completely water saturated). Total carbon mineralization ranged from 15.51 to 112.92 mg C under the treatments for all sites. Carbon mineralization rates decreased with soil depth, increased with temperature, and reached the highest at 60% WHC at the same temperature. The calculated temperature coefficient (Q(10)) values ranged from 1.84 to 2.51 with the soil depths and moisture. However, the values were not significantly affected by soil moisture and depth for all sites due to the different peat properties (P > 0.05). We found that the carbon mineralization could be successfully predicted as a two-compartment function with temperature and moisture (R-2 > 0.96) and total carbon mineralization was significantly affected by temperature and moisture (P < 0.05). Thus, temperature and moisture would play important roles in carbon mineralization of permafrost peatlands in the Great Hing'an Mountains, indicating that the permafrost peatlands would be sensitive to the environment change, and the permafrost peatlands would be potentially mineralized under future climate change.