Data from: 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 changed little in plots with high CMIaverage. The temporal
decrease of ΔAGB in drier areas was attributable to its negative responses
to warming-induced temporal decreases in climate moisture availability. 4.
Synthesis. Our results indicate that large-scale changes in forest carbon
functioning associated with climate change depend on the long-term average
of climate moisture availability. Our finding suggests a possible retreat
of boreal biome at the drier distribution limits with predicted declines
in water availability in the 21st century.