Search

Impervious surfaces (IS) constitute a quantifiable metric for urbanization and ecological environmental assessment. This study estimated the IS in the subtropical coastal area of Xiamen, southeastern China, from TM/OLI images obtained in 1994, 2000, 2004, 2010, and 2015. Two-dimension box-counting and two-dimension multifractal box-counting method were employed to quantitatively characterize the fractal and multifractal features of the spatial patterns of the IS. Results suggest that the spatial patterns observed during the study period are typical fractal structures with scale invariance, and the fractal dimension reveals the spatio-temporal complexity. Increasing the pixel binarization threshold decreases the spatial complexity of the IS pattern. The increasing dimension values over time show that the IS patterns become more complex and the spatial distribution becomes more clustered from 1994 to 2015. The two-dimension multifractal approach can transform an irregular IS pattern into a compact form and amplify small differences between different data series. The results revealed multifractality in the five study years, which varied throughout the study period, but the probability distribution shows a slightly decreasing trend. The probability of a given pixel having a high IS-fraction is consistently high in the study area, as indicated by the positive ratio between the regions where the probability measure appears most concentrated and most sparse.

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 (Q10) 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 (R2 > 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.

Studying the changes of species diversity in plant communities along latitude gradients is important to discover the correlation between biodiversity and environmental factors. Along the main ridges of the Great Xing’an Mountains, 12 natural permafrost wetlands in the valleys were investigated from north to south. Latitudinal changes in species diversity were analyzed with regressive analysis. About 150 plant species were recorded and were found to be in the 12 permafrost wetland plant communities. Most plants belong to the Compositae or Gramineae. The number of family, genus and species increased significantly in the herb layer with decreasing latitude ( P P