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Urban forest has undergone rapid development in China over the last three decades because of the acceleration of urbanization. Urban forest thus plays an increasingly important role in carbon sequestration at a regional and national scale. As one of the most urbanized cities in China, Shanghai showed an increase of forest coverage from 3% in the 1990s to 13% in 2009. Based on CITY-green model and the second soil survey of Shanghai, the forest biomass carbon (FBC) was estimated to be 0.48 Tg in the urban area and, forest soil organic carbon (SOC) (0-100 cm soil depth) is 2.48 Tg in the urban and suburban areas, respectively. These values are relatively within the median and lower level compared with other Chinese megacities, with the FBC of 0.02 Tg in Harbin to 47.29 Tg in Chongqing and the forest SOC of 1.74 Tg in Nanjing to 418.67 Tg in Chongqing. For the different land-use types in Shanghai, the SOC density ranges from 13.8 (tidal field) to 38.6 t ha (agricultural land). On average, the forest SOC density (31.5 t ha) in Shanghai is lower than that in agricultural lands (38.6 t ha) and higher than that in lawns (26.5 t ha) and gardens (21.3 t ha). In Shanghai, the SOC density in newly established urban parks is generally lower than that in older parks. In the northern and southeastern suburban areas (e.g., Baoshan, Yangpu, and Nanhui districts), greenspace SOC density is higher than that in the central commercial areas (Hongkou, Putuo, Changning, and Zhabei districts) and in newly developed district (Pudong District). Uncertainties still exist in the estimation of urban forest carbon in Shanghai, as well as in other Chinese cities. Thus, future research directions are also discussed in this paper. [ABSTRACT FROM AUTHOR]

China is undergoing a rapid urbanization process, and urbanization will have a direct impact on regional ecosystems and affect regional ecosystem services. Considering the mountainous counties in Southwestern China as the research object, this study reveals the spatial clustering characteristics of four typical ecosystem services (food production, soil conservation, water yield and carbon sequestration) as well as the trade-offs and synergies among ecosystem services in different urbanized areas. At the same time, piecewise linear regression is used to determine the threshold of the influence of urbanization on ecosystem services. The results indicate that: 1) There are spatial autocorrelations among the four typical ecosystem services; with strong clustering characteristics, the positive correlation types are "clustered" locally; and with significant spatial heterogeneity, the negative correlation types are scattered and mainly appear in the highly urbanized area. 2) There are also remarkable differences in the relationship among various ecosystem services in different urbanized areas, and in particular, there are marked trade-offs between food production and carbon sequestration in the moderately urbanized area and the highly urbanized area. However, there are synergies between them in the lowly urbanized area. 3) With an increase in the compounded night light index (CNLI), water yield, carbon sequestration, food production and overall ecosystem services values present an increasing-decreasing trend, the soil conservation function value shows a decreasing-increasing trend. The response of water yield, carbon sequestration, food production, and overall ecosystem services to the compounded night light index (CNLI) has a threshold of 1.2642, 1.4833, 1.3388, 1.5146 and 1.2237, respectively. Based on the detected relationships between urbanization and ecosystem services, this study provides a theoretical reference for the selection of urbanization development models in key ecological functional areas. [ABSTRACT FROM AUTHOR]