Changes in growth of pristine boreal North American forests from 1950 to 2005 driven by landscape demographics and species traits

Girardin, Martin P.; Guo, Xiaojing; Bernier, Pierre Y.; Raulier, Frédéric; Gauthier, Sylvie

doi:10.5194/bg-9-2523-2012

Cited by 55 publications

(45 citation statements)

References 57 publications

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“…The CO 2 fertilization effect would increase plant productivity until a concentration threshold (Amthor ), whereas the increased temperature effect on productivity is still debated (Way & Sage ; Girardin et al . ).…”

Section: Discussionmentioning

confidence: 97%

Long‐term fire history in northern Quebec: implications for the northern limit of commercial forests

Asselin

Finsinger

Hély

et al. 2014

Journal of Applied Ecology

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Summary1. Fire frequency is expected to increase in boreal forests over the next century owing to climate change. In Quebec (Canada), the location of the northern limit of commercial forests (c. 51°N) was established in 2000 taking into account mainly forest productivity and fire risk. The location of the limit is currently under debate and is being re-evaluated based on a more extensive survey of the territory. We characterized the natural variability of fire occurrence (FO) in the area surrounding the northern limit, and these results are a useful contribution to discussions on the re-evaluation of its location. 2. Regional FO over the last 7000 years was reconstructed from sedimentary charcoal records from 11 lakes located in three regions surrounding the northern limit (i.e. south, north and near the limit). Holocene simulated precipitation and temperature from a general circulation model (GCM) were used to identify the long-term interactions between climate and fire. 3. Fire histories displayed similar trends in all three regions, with FO increasing from 7000 calibrated years before present (cal. years BP) to reach a maximum at 4000-3000 cal. years BP, before decreasing during the late-Holocene. This trend matches the simulated changes in climate, characterized by drier and warmer conditions between 7000 and 3500 cal. years BP and cooler and moister conditions between 3500 and 0 cal. years BP. 4. Northern ecosystems displayed higher sensitivity to climate change. The natural variability of FO was narrower in the southern region compared with the limit and northern regions. An abrupt decrease in FO was recorded close to and north of the limit at 3000 cal. years BP, whereas the decrease was more gradual in the south. 5. Synthesis and applications. We reconstructed the natural variability in fire activity over the last 7000 years near the current location of the northern limit of commercial forests in Quebec. Fire occurrences were more sensitive to climate change near to and north of the limit of commercial forestry. In the context of predicted increase in fire activity, the lower resilience of northern forests advocates against a northern repositioning of the limit of commercial forests.

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Section: Discussionmentioning

confidence: 97%

Long‐term fire history in northern Quebec: implications for the northern limit of commercial forests

Asselin

Finsinger

Hély

et al. 2014

Journal of Applied Ecology

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“…As noted by Girardin et al . (), the productivity drivers may vary with the demography of stands. Under increasing stand disturbances, the forest age structure will change toward younger age stands and this could reduce future autotrophic respiration and water dependence.…”

Section: Discussionmentioning

confidence: 99%

Negative impacts of high temperatures on growth of black spruce forests intensify with the anticipated climate warming

Girardin

Hogg

Bernier

et al. 2015

Global Change Biology

162

126

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An increasing number of studies conclude that water limitations and heat stress may hinder the capacity of black spruce (Picea mariana (Mill.) B.S.P.) trees, a dominant species of Canada's boreal forests, to grow and assimilate atmospheric carbon. However, there is currently no scientific consensus on the future of these forests over the next century in the context of widespread climate warming. The large spatial extent of black spruce forests across the Canadian boreal forest and associated variability in climate, demography, and site conditions pose challenges for projecting future climate change responses. Here we provide an evaluation of the impacts of climate warming and drying, as well as increasing [CO2 ], on the aboveground productivity of black spruce forests across Canada south of 60°N for the period 1971 to 2100. We use a new extensive network of tree-ring data obtained from Canada's National Forest Inventory, spatially explicit simulations of net primary productivity (NPP) and its drivers, and multivariate statistical modeling. We found that soil water availability is a significant driver of black spruce interannual variability in productivity across broad areas of the western to eastern Canadian boreal forest. Interannual variability in productivity was also found to be driven by autotrophic respiration in the warmest regions. In most regions, the impacts of soil water availability and respiration on interannual variability in productivity occurred during the phase of carbohydrate accumulation the year preceding tree-ring formation. Results from projections suggest an increase in the importance of soil water availability and respiration as limiting factors on NPP over the next century due to warming, but this response may vary to the extent that other factors such as carbon dioxide fertilization, and respiration acclimation to high temperature, contribute to dampening these limitations.

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“…In summary, our results support the hypothesis that these forests' responses to climate ‘are dependent on demographic and species traits via their mediation of temperature and water stress constraints’ (Girardin et al ., ), while emphasizing that demography is significantly complicated by the legacies of past disturbances (Gough et al ., ). We observed significant temperature‐ and precipitation‐driven patterns in ring width superimposed on slower patterns of recovery from past disturbance.…”

Section: Discussionmentioning

confidence: 99%

Disturbance legacies and climate jointly drive tree growth and mortality in an intensively studied boreal forest

Bond‐Lamberty

Rocha

Calvin

et al. 2013

Global Change Biology

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Most North American forests are at some stage of post-disturbance regrowth, subject to a changing climate, and exhibit growth and mortality patterns that may not be closely coupled to annual environmental conditions. Distinguishing the possibly interacting effects of these processes is necessary to put short-term studies in a longer term context, and particularly important for the carbon-dense, fire-prone boreal forest. The goals of this study were to combine dendrochronological sampling, inventory records, and machine-learning algorithms to understand how tree growth and death have changed at one highly studied site (Northern Old Black Spruce, NOBS) in the central Canadian boreal forest. Over the 1999-2012 inventory period, mean tree diameter increased even as stand density and basal area declined significantly. Tree mortality averaged 1.4 AE 0.6% yr À1, with most mortality occurring in medium-sized trees; new recruitment was minimal. There have been at least two, and probably three, significant influxes of new trees since stand initiation, but none in recent decades. A combined tree ring chronology constructed from sampling in 2001, 2004, and 2012 showed several periods of extreme growth depression, with increased mortality lagging depressed growth by~5 years. Higher minimum and maximum air temperatures exerted a negative influence on tree growth, while precipitation and climate moisture index had a positive effect; both current-and previous-year data exerted significant effects. Models based on these variables explained 23-44% of the ring-width variability. We suggest that past climate extremes led to significant mortality still visible in the current forest structure, with decadal dynamics superimposed on slower patterns of fire and succession. These results have significant implications for our understanding of previous work at NOBS, the carbon sequestration capability of old-growth stands in a disturbanceprone landscape, and the sustainable management of regional forests in a changing climate.

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Changes in growth of pristine boreal North American forests from 1950 to 2005 driven by landscape demographics and species traits

Cited by 55 publications

References 57 publications

Long‐term fire history in northern Quebec: implications for the northern limit of commercial forests

Long‐term fire history in northern Quebec: implications for the northern limit of commercial forests

Negative impacts of high temperatures on growth of black spruce forests intensify with the anticipated climate warming

Disturbance legacies and climate jointly drive tree growth and mortality in an intensively studied boreal forest

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