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Inconsistent estimates of forest biomass carbon stocks (BCS) in China have been reported in recent decades using inventory data. This study was to update China's forest biomass carbon sink based on seven forest inventories from 1973 to 2008 and to identify the relative contributions to such sink from changes in forest area and biomass carbon density (BCD) as a result of growth, plantation and harvests in different regions. Our results indicated that total BCS of all forest types, including forest stands and other forest types (economic forests, woodlands, shrub forests, bamboo forests and trees on non-forest lands), increased by 65 % from 1973 to 2008 and recently reached 8.12 Pg C. Total BCS and BCD of forest stands (canopy coverage >20 %) increased from 4.11 Pg C and 35.10 Mg C ha to 6.24 Pg C and 40.12 Mg C ha during the study period, respectively. Forest stands acted as a biomass carbon sink of 0.17 Pg C year, which accounts for 84.4 % of the total sink of all forest types from 1999 to 2008 and have great potential to absorb more biomass carbon in the future due to large fractions of young and middle aged forests, which are increasing BCD. BCS of forest stands increased in all regions but the northeast region. Their biomass carbon sink was mainly driven by the BCD increase in the densely populated south and east regions and by the expansion of forest areas in the north, northwest, and southwest regions with abundant land resources. [ABSTRACT FROM AUTHOR]

Abstract: Vegetation fractional coverage (VFC) is an important vegetation parameter affecting exchanges of carbon, water, energy between the atmosphere and surface. In this study, the applicability of tonal and texture measures calculated using an IKONOS_2 image in retrieving VFC of forests was investigated in the urban area of Nanjing city, China. Four spectral vegetation indices (VI) and six texture measures (TEX) were related to VFCs acquired from in situ measurements. Models for estimating VFC based on VIs or/and TEXs were established and validated for planted low broad-leaf forest plots (PLB), planted mature forest plots (PMF), natural broad-leaf forest plots (NBF), and all forest plots (ALLv), respectively. The results show that high spatial resolution remote sensing data is applicable to estimate VFC in urban areas, and TEXs may act as effective supplements of vegetation indices (VIs) for the retrieval of VFC. VIs are suitable for VFC estimation of mature forests (such as NBF and PMF) with high vegetation density, and TEXs can yield a more accurate estimate for planted forests (such as PLB and PMF) with regular spatial distribution if they are calculated with proper parameters, such as window size. The combination of VIs and TEXs improve the estimation of VFC if forest types are not previously differentiated. The results can be used as a reference for determining effective spectral or texture parameters in VFC estimation under similar environmental conditions according to vegetation maturity and regularity. [Copyright &y& Elsevier]