Soil carbon change and its affecting factors following afforestation in China

The effects of afforestation on soil carbon (C) stocks are of concern to the plantation carbon budget and the mitigation of global warming. China has the largest tree plantation areas in the world, but the effects of afforestation on soil C are poorly understood. We reviewed Chinese data of soil C, available from 70 publications, to analyze the change of soil C and its affecting factors following afforestation. Our results indicated that afforestation could accumulate soil C in China, with the accumulation rate of 42.05, 30.07 and 73.94 g C m−2 yr−1 in 0–20, 20–40 and 0–40 cm soil depths. Five years after afforestation, plantations began to accumulate soil C rapidly, and plantations with the age of 10–20 years old had the highest soil C accumulation rate. Afforestation on former cropland and wasteland had higher accumulation rates of soil C than on former grassland. In middle-temperature and warmer regions, the accumulation rate of soil C was higher than that in colder regions, and in semi-humid regions, the accumulation rate of soil C was significantly higher than that in semi-arid regions. Soil C accumulated rapidly in broadleaved and mixed plantations, and the accumulation rate in broadleaved was higher than that in coniferous plantations. Although some uncertainties existed with regard to the data and methods, a reasonable analysis of soil C change following afforestation in China was achieved for the first time. Future studies should be fulfilled with improved sampling and analytical techniques, reliable soil carbon models and synchronous investigation of soil nitrogen dynamics.