Canadian Forest Service Publications
Divergent temporal trends of net biomass change in western Canadian boreal forests. 2018. Luo, Y., Chen, H.Y.H., McIntire, E.J.B., Andison, D.W. Journal of Ecology. 107:69–78.
Issued by: Pacific Forestry Centre
Catalog ID: 40039
Availability: PDF (download)
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- 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 above‐ground biomass change (ΔAGB) can help infer how forest carbon sequestration responds to ongoing 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 CMICMIaverage remain unclear.
- We tested the hypothesis that the negative impacts of climate change on ΔAGB would decrease with CMICMIaverage using the data from permanent sample plots, monitored from 1958 to 2011, with stand ages varying from 17 to 210 years, in western boreal forests of Canada.
- We found that ΔAGB on average increased with CMICMIaverage. Temporally, ΔAGB declined sharply between 1958 and 2011 in plots with low CMICMIaverage owing to increased biomass loss from mortality accompanied by little growth gain, whereas ΔAGB changed little in plots with high CMICMIaverage. The temporal decrease of ΔAGB in drier areas was attributable to its negative responses to warming‐induced temporal decreases in climate moisture availability.
- 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.
Plain Language Summary
Current predictions of whether tree growth in Canada’s forests is going to be enhanced or reduced by climate change are idiosyncratic. In other words, there are different results coming from different studies in different locations, with no clear explanation for the differences. In this study, we show that across a rainfall and temperature gradient in central Canada, the changes are directly related to moisture. If there is enough moisture, then trees appear to be growing better; if there is not enough moisture, trees appear to grow worse. This clarification of the divergent results from elsewhere will help scientists forecast future growth better than previously.