Preliminary study on carbon fluxes from land change in a subtropical watershed of China

This study represents a watershed-scale study of C fluxes from land change in the Jiulong River watershed, a subtropical watershed in Southeast China. Land-cover maps of woodland, cropland, orchard, built-up, water, and barren from 1986, 1996, 2002, 2007, 2010 were produced using a combination of unsupervised classification and spatial reclassification based on manual on-screen digitizing. Intensity analysis was then used to identify the dominant and systematic transitions. C fluxes from land change over three decades of imagery were estimated from the transitions among woodland, cropland, built and orchard for each time period. C accumulation and losses from terrestrial biomass are derived from observed changes in land cover. The ecological method used in this study considered that the amount of C emitted to the atmosphere is a function of the amount of C stored in terrestrial vegetation and the areal extent of each land-use category, combined with key terms of biomass, annual carbon gain, and burning efficiency. The results indicate that the trend of LUCC in Jiulong River watershed can produce a considerable potential of function as an important Carbon sink in south-eastern China, the net amount of carbon stored can be 4.50×10⁴ t, 1.86×10⁵ t, 9.21×10⁵ t, 1.35×10⁵ t for 1986–1996, 1996–2002, 2002–2007, and 2007–2010, respectively. The findings of this study enable us to gain a broad understanding of watershed-scale C fluxes from land change in a subtropical watershed of China.