Precarious resilience of the boreal forest of eastern North America during the Holocene

Couillard, Pierre-Luc; Payette, Serge; Lavoie, Martin; Frégeau, Mathieu

doi:10.1016/j.foreco.2021.118954

Cited by 5 publications

(2 citation statements)

References 63 publications

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“…For sites where black spruce was present but not dominant prefire (121 sites mainly dominated by jack pine or broadleaf taxa), it seldom expanded (<10% of sites). Detailed paleoecological studies of boreal forest vegetation during the Holocene indicate a high resilience of black spruce–dominated stands to frequent fire ( 30 – 32 ), consistent with early contemporary studies of postfire regeneration ( 33 – 35 ); this suggests that the loss of resilience documented here is a shift from the historic norm. On average, spruce regeneration failed (i.e., no spruce recruitment) in 18% of sites (range: 10 to 25%) across North America ( Fig.…”

Section: Resultssupporting

confidence: 85%

Increasing fire and the decline of fire adapted black spruce in the boreal forest

Baltzer

Day

Walker

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

143

129

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Intensifying wildfire activity and climate change can drive rapid forest compositional shifts. In boreal North America, black spruce shapes forest flammability and depends on fire for regeneration. This relationship has helped black spruce maintain its dominance through much of the Holocene. However, with climate change and more frequent and severe fires, shifts away from black spruce dominance to broadleaf or pine species are emerging, with implications for ecosystem functions including carbon sequestration, water and energy fluxes, and wildlife habitat. Here, we predict that such reductions in black spruce after fire may already be widespread given current trends in climate and fire. To test this, we synthesize data from 1,538 field sites across boreal North America to evaluate compositional changes in tree species following 58 recent fires (1989 to 2014). While black spruce was resilient following most fires (62%), loss of resilience was common, and spruce regeneration failed completely in 18% of 1,140 black spruce sites. In contrast, postfire regeneration never failed in forests dominated by jack pine, which also possesses an aerial seed bank, or broad-leaved trees. More complete combustion of the soil organic layer, which often occurs in better-drained landscape positions and in dryer duff, promoted compositional changes throughout boreal North America. Forests in western North America, however, were more vulnerable to change due to greater long-term climate moisture deficits. While we find considerable remaining resilience in black spruce forests, predicted increases in climate moisture deficits and fire activity will erode this resilience, pushing the system toward a tipping point that has not been crossed in several thousand years.

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Section: Resultssupporting

confidence: 85%

Increasing fire and the decline of fire adapted black spruce in the boreal forest

Baltzer

Day

Walker

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

143

129

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“…Contrary to jack pine, black spruce is on both ends of the fire disturbance gradient and less constrained by fire frequency and soil drainage. The species is also able to regenerate rapidly after fire in dry and wet environments ( 39 , 47 , 48 ).…”

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confidence: 99%

The velocity of postglacial migration of fire-adapted boreal tree species in eastern North America

Payette

Couillard

Frégeau

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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The Earth’s climate has been warming rapidly since the beginning of the industrial era, forcing terrestrial organisms to adapt. Migration constitutes one of the most effective processes for surviving and thriving, although the speed at which tree species migrate as a function of climate change is unknown. One way to predict latitudinal movement of trees under the climate of the twenty-first century is to examine past migration since the Last Glacial Maximum. In this study, radiocarbon-dated macrofossils were used to calculate the velocity of past migration of jack pine ( Pinus banksiana ) and black spruce ( Picea mariana ), two important fire-adapted conifers of the North American boreal forest. Jack pine migrated at a mean rate of 19 km per century (km -cent ) from unglaciated sites in the central and southeastern United States to the northern limit of the species in subarctic Canada. However, the velocity increased between unglaciated and early deglaciated sites in southern Quebec and slowed from early to mid-Holocene in central and eastern Quebec. Migration was at its lowest speed in late-Holocene times, when it stopped about 3,000 y ago. Compared with jack pine, black spruce migrated at a faster mean rate of 25 km -cent from the ice border at the last interstadial (Bølling/Allerød) to the species tree limit. The modern range of both species was nearly occupied about 6,000 y ago. The factors modulating the changing velocity of jack pine migration were closely associated with the warm-dry climate of the late Pleistocene–Holocene transition and the more humid climate of the mid- and late-Holocene.

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Ecological Classification in Forest Ecosystem Management: Links Between Current Practices and Future Climate Change in a Québec Case Study

Grondin

Brice

Boulanger

et al. 2023

Advances in Global Change Research

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Climate change is expected to profoundly impact boreal forests, ranging from changes in forest composition and productivity to modifications in disturbance regimes. These climate-induced changes represent a major challenge for forest ecosystem management, as information based on ecological classification may no longer provide a straightforward guide for attaining management goals in the future. In this chapter, we examine how climate change could influence the use of ecological classification and by what means this approach can continue to be relevant for guiding the ongoing development of management practices. We address these questions by first describing ecological classification, using the example of Québec’s classification system, and then showing its importance in forest ecosystem management. Using a forest landscape in Québec as a case study, we then look at how climate change could affect boreal forest ecosystems by presenting a detailed, multistep analysis that considers climate analogs, habitat suitability, and changes in forest composition. We show that at the end of the century, the vegetation of the Abies-Betula western subdomain will not change sufficiently to resemble that of its climate analog, currently located ~500 km to the south. Changes in fire frequency and severity could significantly modify forest dynamics and composition. Consequently, the potential vegetation and the successional pathways defined under the current climate could change and follow new successional trajectories. This possible reality forces us to question some fundamental aspects of ecological classification. However, we argue that ecological classification can still provide a valuable framework for future forest management, particularly in continuing to recognize the various types of ecosystems present along toposequences. Given the changes expected in forest vegetation composition and dynamics, future variability and uncertainty must be integrated into the current stable classification units and predictable successional trajectories of ecological classification.

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Precarious resilience of the boreal forest of eastern North America during the Holocene

Cited by 5 publications

References 63 publications

Increasing fire and the decline of fire adapted black spruce in the boreal forest

Increasing fire and the decline of fire adapted black spruce in the boreal forest

The velocity of postglacial migration of fire-adapted boreal tree species in eastern North America

Ecological Classification in Forest Ecosystem Management: Links Between Current Practices and Future Climate Change in a Québec Case Study

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