Carbon sink capacity in northern forests reduced by global warming

Losing more than we gain from autumn warming in the north

Flux tower on a recently harvest boreal black spruce site with lowbush blueberry ground cover, Chibougamau, Quebec. Click here for more information.

An international study investigating the carbon sink capacity of northern terrestrial ecosystems discovered that the duration of the net carbon uptake period (CUP) has on average decreased due to warmer autumn temperatures.

Net carbon uptake of northern ecosystems is decreasing in response to autumnal warming according to findings recently published January 3rd, in the journal Nature. The carbon balance of terrestrial ecosystems is particularly sensitive to climatic changes in autumn and spring. Over the past two decades autumn temperatures in northern latitudes have risen by about 1.1 °C with spring temperatures up by 0.8 °C.

Mont Wright, a northern hardwood forest near Quebec City, Canada. Click here for more information.

Many northern terrestrial ecosystems currently lose carbon dioxide (CO₂) in response to autumn warming, offsetting 90% of the increased carbon dioxide uptake during spring. Using computer modeling to integrate forest canopy measurements and remote satellite data, researchers found that while warm spring temperatures accelerate growth more than soil decomposition and enhance carbon uptake, autumn warming greatly increases soil decomposition and significantly reduces carbon uptake.

Lead author of the study, Dr. Shilong Piao from the LSCE, UMR CEA-CNRS,in France says “If warming in autumn occurs at a faster rate than in spring, the ability of northern ecosystems to sequester carbon will diminish in the future”.

Philippe Ciais also, a member of the research team and a scientist from the Global Carbon Project says “The potentially rapid decline in the future ability of northern terrestrial ecosystems to remove atmospheric carbon dioxide would make stabilization of atmospheric CO₂ concentrations much harder than currently predicted”.

Mixed beech forest in the mountains of a warm temperate region in China. Click here for more information.

This study was supported by European Community-funded projects ENSEMBLES and CARBOEUROPE IP, and by the National Natural Science Foundation of China as well as by Fluxnet-Canada, which was supported by CFCAS, NSERC, BIOCAP, MSC and NRCan.

“Net carbon dioxide losses of northern ecosystems in response to autumn warming” Shilong Piao, Philippe Ciais, Pierre Friedlingstein, Philippe Peylin, Markus Reichstein, Sebastiaan Luyssaert, Hank Margolis, Jingyun Fang, Alan Barr, Anping Chen, Achim Grelle, David Hollinger, Tuomas Laurila, Anders Lindroth, Andrew D. Richardson & Timo Vesala