Understanding the location of carbon sources and sinks is essential for accurately predicting future changes in atmospheric carbon dioxide and climate. Mid- to high- latitude terrestrial ecosystems are well known to be the principal carbon sink regions, yet with less attention to the mid- to low-latitude ecosystems. 

Prof. YU Guirui and his cooperators, Synthesis Research Center of Chinese Ecosystem Research Network, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, integrated eddy covariance observations from ChinaFlux, AsiaFlux, AmeriFlux, CarboEurope and FLUXNET to show that East Asian monsoon subtropical forests between 20°N and 40°N represent an average net ecosystem productivity (NEP) of 362 ± 39 g C m^-2 yr^-1 in the 1990s and 2000s.  

This average forest NEP value is higher than that in Asian tropical and temperate forests and the same latitudes Europe-Africa and North America forests. This NEP is comparable to that in Southeastern US subtropical forests and intensively managed Western European forests. The total NEP of East Asian monsoon subtropical forests was estimated to be 0.72 ± 0.08 Pg C yr^-1 which accounts for 8 % of the global forest NEP.  

This result indicates that the role of subtropical forests in the current global carbon cycle cannot be ignored and that the regional distributions of the northern hemisphere's terrestrial carbon sinks are needed to be re-evaluated.  

The underlying mechanisms for this high carbon uptake in East Asian monsoon subtropical forests revealed to be attributed to the combined effects of the young stand ages, high nitrogen deposition and sufficient and synchronous water and heat availability. 

The related study has been published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS) (Guirui Yu, Zhi Chen, Shilong Piao, Changhui Peng, Philippe Ciais, Qiufeng Wang, Xuanran Li, Xianjin Zhu. High carbon dioxide uptake by subtropical forest ecosystems in the East Asian monsoon region. Proceedings of the National Academy of Sciences of the United States of America, 2014, 111(13): 4910-4915).