Increasing carbon storage in subtropical forests over the Yangtze River basin and its relations to the major ecological projects

Forest carbon stocks has an important role in the global carbon budget. Based on the satellite-observed and LPJ model simulated aboveground biomass carbon (ABC) data, the spatial and temporal changes of subtropical forest carbon storage in the Yangtze River basin and its relations to the climate variation and human activities were analyzed by using the methods of cumulative curve analysis and climate sensitivity analysis during 1993-2012. The results revealed that: (1) In general, the forest ABC increased obviously in the Yangtze River basin during the past 20 years, and the ABC rose from 2563.91 Tg C in 1993 to 2893.17 Tg C in 2012, with a growth rate of 12.84%. The higher ABC distribution was mainly concentrated in the Jialing River basin and Hanjiang River basin and the significantly increasing trends could be found in most area of the Yangtze River basin; (2) The forest ABC was sensitive to the changes of temperature and precipitation. When the temperature increases by 1 degrees C, the ABC in the Yangtze River basin will increase by 3.32%, while it will decrease by -6.12% when the precipitation increases by 10%; (3) The forest ABC growth rate had accelerated from 3.15% in 1993-2000 to 8.01% in 2001-2012. The cumulative curve of the forest ABC was generally higher than the temperature or the precipitation after 2000. The total areas induced by climate variation and human activities accounted for 30.5% and 52.59% with an increases in ABC by 67.52 Tg C and 188.74 Tg C from 1993 to 2012, respectively. The implementation of major forestry projects might be the main reason for the rapid increase of forest ABC in the Yangtze River basin. This study suggested human activities such as ecological projects might contribute to the accelerated greening trend and highlighted the pivotal role of subtropical forest ABC in the carbon budget in China. (C) 2019 Elsevier B.V. All rights reserved.