Biomass Carbon Sequestration by Planted Forests in China

The planted forest area and carbon sequestration have increased significantly in China,because of large-scale reforestation and afforestation in the past decades.In this study,we developed an age-based volume-to-biomass method to estimate the carbon storage by planted forests in China in the period of 1973-2003 based on the data from 1209 field plots and national forest inventories.The results show that the total carbon storage of planted forests was 0.7743 Pg C in 1999-2003,increased by 3.08 times since the early 1970s.The carbon density of planted forests varied from 10.6594 Mg/ha to 23.9760 Mg/ha and increased by 13.3166 Mg/ha from 1973-1976 to 1999-2003.Since the early 1970s,the planted forests in China have been always a carbon sink,and the annual rate of carbon sequestration was 0.0217 Pg C/yr.The carbon storage and densities of planted forests varied greatly in space and time.The carbon storage of Middle South China was in the lead in all regions,which accounted for 23%-36% of national carbon storage.While higher C densities (from 17.79 Mg/ha to 26.05 Mg/ha) were usually found in Northeast China.The planted forests in China potentially have a high carbon sequestration since a large part of them are becoming mature and afforestation continues to grow.

Impacts of land-use and climate changes on ecosystem productivity and carbon cycle in the cropping-grazing transitional zone in China

The impact of land-use/land-cover and climate changes on ecosystem productivity and carbon cycle is one of the most important issues in global change studies.In the past 20 years,the climate and land-use in China have changed significantly and have had important ecological consequences,especially in ecologically sensitive regions,e.g.the cropping-grazing transition zone(CGTZ).Here we present a study that used a process-based ecosystem model and data of land-use changes based on remote sensing and of climate change at high spatial and temporal resolution to estimate the impacts of land-use and climate changes on net primary productivity(NPP),vegetation carbon storage,soil heterotrophic respiration(HR),carbon storage and net ecosystem productivity(NEP)in the CGTZ of China.The results show that the warming and decreases in precipitation in CGTZ reduced NPP by 3.4%,increased HR by 4.3%,and re-duced annual mean total NEP by 33.7Tg from the 1980s to the 1990s.Although carbon storage in vegetation and soil was increasing because the mean NPP for the period was higher than HR,the decreasing NEP indicate that climate change reduced the carbon uptake rate.However,land-use changes in this zone caused increases in NPP by 3.8%,vegetation carbon storage by 2.4%,and annual total NEP by 0.59Tg.The land-use changes enhanced ecosystem carbon up-take,but not enough to offset the negative effect of the climate change.The climate change had greater impacts than the land-use change for the whole CGTZ zone,but had smaller impacts than the land-use change in the regions where it occurred.

Prediction of carbon exchanges between China terrestrial ecosystem and atmosphere in 21st century

The projected changes in carbon exchange between China terrestrial ecosystem and the atmosphere and vegetation and soil carbon storage during the 21st century were investigated using an atmos-phere-vegetation interaction model (AVIM2). The results show that in the coming 100 a, for SRES B2 scenario and constant atmospheric CO2 concentration, the net primary productivity (NPP) of terrestrial ecosystem in China will be decreased slowly, and vegetation and soil carbon storage as well as net ecosystem productivity (NEP) will also be decreased. The carbon sink for China terrestrial ecosystem in the beginning of the 20th century will become totally a carbon source by the year of 2020, while for B2 scenario and changing atmospheric CO2 concentration, NPP for China will increase continuously from 2.94 GtC·a?1 by the end of the 20th century to 3.99 GtC·a?1 by the end of the 21st century, and vegetation and soil carbon storage will increase to 110.3 GtC. NEP in China will keep rising during the first and middle periods of the 21st century, and reach the peak around 2050s, then will decrease gradually and approach to zero by the end of the 21st century.