Canadian Forest Service Publications

No growth stimulation of Canada’s boreal forest under half-century of combined warming and CO2 fertilization. 2016. Girardin, M.P.; Bouriaud, O.; Hogg, E.H.; Kurz, W.A.; Zimmermann, N.E.; Metsaranta, J.; de Jong, R.; Frank, D.C.; Esper, J.; Büntgen, U.; Guo, X.J.; Bhatti, J. Proc. Natl. Acad. Sci. USA 113: E8406-E8414.

Year: 2016

Issued by: Laurentian Forestry Centre

Catalog ID: 37463

Language: English

Availability: PDF (download)

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Considerable evidence exists that current global temperatures are higher than at any time during the past millennium. However, the long-term impacts of rising temperatures and associated shifts in the hydrological cycle on the productivity of ecosystems remain poorly understood for mid to high northern latitudes. Here, we quantify species-specific spatiotemporal variability in terrestrial aboveground biomass stem growth across Canada’s boreal forests from 1950 to the present. We use 873 newly developed tree-ring chronologies from Canada’s National Forest Inventory, representing an unprecedented degree of sampling standardization for a large-scale dendrochronological study. We find significant regional- and species-related trends in growth, but the positive and negative trends compensate each other to yield no strong overall trend in forest growth when averaged across the Canadian boreal forest. The spatial patterns of growth trends identified in our analysis were to some extent coherent with trends estimated by remote sensing, but there are wide areas where remote-sensing information did not match the forest growth trends. Quantifications of tree growth variability as a function of climate factors and atmospheric CO2 concentration reveal strong negative temperature and positive moisture controls on spatial patterns of tree growth rates, emphasizing the ecological sensitivity to regime shifts in the hydrological cycle. An enhanced dependence of forest growth on soil moisture during the late-20th century coincides with a rapid rise in summer temperatures and occurs despite potential compensating effects from increased atmospheric CO2 concentration.

Plain Language Summary

In this study, the researchers quantified the variability in stem biomass growth of 19 tree species across Canada’s boreal forest from 1950 to 2002. The researchers found regional and species trends in biomass growth. However, since there are positive and negative trends, they offset each other. Therefore, there is no global trend in forest growth when compared to the average of Canada’s boreal forests.

Tree growth varies according to climatic factors and atmospheric CO2 concentration. Even though CO2 promotes tree growth, the increase in summer temperature offsets this effect by reducing the quantity of water available in the soil. These results highlight the ecological sensitivity of Canada’s boreal forest to changes in the water regime.

Forest managers, planners and decision-makers responsible for drafting regulations, guidelines, rules and laws related to forest management as well as the scientific community are the target audience of this publication that clarifies the impact of climate change on forest growth.