Divergent temporal trends of net biomass change in western Canadian boreal forests

1. Forests play a strong role in the global carbon cycle by absorbing atmospheric carbon dioxide through increasing forest biomass. Understanding temporal trends of forest net aboveground biomass change (ΔAGB) can help infer how forest carbon sequestration responds to on-going climate changes. Despite wide spatial variation in the long-term average of climate moisture availability (CMIaverage) across forest ecosystems, temporal trends of ΔAGB associated with CMIaverage remains unclear. 2. We tested the hypothesis that the extent of negative impacts of climate change on ΔAGB would decrease with CMIaverage using the data from permanent sample plots of varying ages from 17 to 210 years, monitored from 1958 to 2011 in western boreal forests of Canada. 3. We found that ΔAGB on average increased with CMIaverage. Temporally, ΔAGB declined sharply between 1958 and 2011 in plots with low CMIaverage owing to increased biomass loss from mortality accompanied by little growth gain, whereas ΔAGB cha...