Arctic and boreal ecosystems in the northern high latitudes (such as forests and wetlands) are responsible for soaking up large amounts of carbon dioxide (CO₂) released by burning fossil fuels like coral and oil through photosynthesis. Plants absorb CO₂ out of the atmosphere and return oxygen to the atmosphere, which is called carbon sinks. Carbon sinks help to combat climate change because CO₂ traps more sun’s heat and is one of the reasons why average global temperatures have been climbing over in the last few decades.

High-latitude ecosystems are generally limited by cold temperature. Climate warming contributes to stronger carbon sinks in the early growing season through promoting earlier thawing, earlier onset of vegetation productivity, and longer growing seasons, and thus benefits photosynthesis more than respiration. However, seasonal dynamics of net CO₂ uptake in response to temperature anomalies remain uncertain.

A collaborative study led by Dr. LIU Zhihua from the Institute of Applied Ecology, Chinese Academy of Sciences (CAS) and Dr. WANG Wenjuan from the Northeast Institute of Geography and Agroecology, CAS assessed how temperature anomalies affect seasonal CO₂ exchange. The net CO₂ seasonal cycle and climatic and environmental controls across Alaska and northwestern Canada during the anomalously warm winter to spring conditions in 2015 and 2016 were investigated by complementary in situ measurements, model simulations (TRENDY, Atmospheric CO₂ inversions), and satellite observations (NASA Soil Moisture Active Passive mission Level 4 Carbon product).It is found that photosynthesis was enhanced more than respiration in the warming spring, leading to greater CO₂ uptake. However, photosynthetic enhancement from spring warming was partially offset by greater respiration during the preceding anomalously warm winter, resulting in nearly neutral effects on the annual net CO₂ balance. Air temperature was a primary influence on net CO₂ exchange in winter and spring, while soil moisture was a primary control on net CO₂ exchange in the fall. Findings was published in Global Change Biology.

"The results suggested that seasonal compensation in the carbon cycle is widespread during a warm winter to spring transition, and under warmer climates, the carbon cycle in the high-latitude ecosystems may be increasingly controlled by hydrologic conditions and subject to much larger uncertainty due to poor understanding of future moisture conditions and their large spatial heterogeneity" said Dr. WANG Wenjuan.

Dr. WANG Wenjuan, Ph.D, Principal Investigator

Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences

www.iga.ac.cn

Changchun, Jilin, 130102, China

Tel. 0431-82536094

E-mail: wangwenj@iga.ac.cn