North American Boreal Forests Are a Large Carbon Source Due to Wildfires From 1986 to 2016

Zhao, Bailu; Zhuang, Qianlai; Shurpali, Narasinha J.; Köster, Kajar; Berninger, Frank; Pumpanen, Jukka

doi:10.21203/rs.3.rs-108154/v1

Cited by 5 publications

(8 citation statements)

References 55 publications

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“…We also identified that wildfires contribute largely to carbon loss, evidencing that 2015–2017 period presented the highest C losses which coincides with Zhao et al. (2021) who identified that this year was the highest loss since 1986. We identified that our C loss estimation has the same pattern that forest losses detected by van Wees et al.…”

Section: Discussionsupporting

confidence: 89%

Analyzing the Spatiotemporal Patterns of Forests Carbon Sink and Sources Between 2000 and 2019

et al. 2022

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Here we present a global time‐series of global forest above ground biomass from 2000 to 2019, analyzing spatiotemporal patterns of carbon balance, accounting for losses and gains. We generated a global Above‐Ground Biomass (AGB) map for the year 2000 and assessed its correlation with different satellite products. We generated a multi‐year analysis of AGB changes at the pixel level was generated, estimating carbon (C) loss and gain. Finally, we estimated the C losses due to forest clearing and wildfires analyzing their trends across biomes and countries. Our results show that the global mean annual loss was 2.88 ± 0.33 PgC yr−1, while global mean C gain was 2.95 ± 0.43 PgC yr−1, resulting in a neutral to sink behavior of −0.06 ± 0.58 PgC yr−1. The mean annual C loss by forest clearing was 1.04 ± 0.03 PgC yr−1, with an increasing trend of +0.03 ± 0.01 PgC yr−1. Eight biomes and 54 countries showed a significant increasing trend of C loss by forest clearing. Wildfires C losses reached 0.351 ± 0.02 Pg C yr−1, representing the 33.71% of forest clearing C losses. Boreal forest presented the highest C losses from wildfires, while significant increasing trends were evidenced in five biomes. We also find increasing trends of wildfire C loss in 20 countries while decreasing trends were identified in 10 countries. Our findings highlight the importance of designing strong policies to halt deforestation as agreed in the recent COP26 and provide information to identify priority areas to start implementing these policies in the short term.

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Section: Discussionsupporting

confidence: 89%

Analyzing the Spatiotemporal Patterns of Forests Carbon Sink and Sources Between 2000 and 2019

et al. 2022

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“…In line with the general recognition of North American forests acting as a carbon sink (Pan et al, 2011), we observed either a positive or neutral net NABP in the Northern American Boreal and Temperate regions. Negative NABP estimates were also observed locally that could be associated with fire regimes (Zhao et al, 2021).…”

Section: Discussionmentioning

confidence: 97%

Global sensitivities of forest carbon changes to environmental conditions

Besnard

Santoro

Cartus

et al. 2021

Global Change Biology

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The responses of forest carbon dynamics to fluctuations in environmental conditions at a global scale remain elusive. Despite the understanding that favourable environmental conditions promote forest growth, these responses have been challenging to observe across different ecosystems and climate gradients. Based on a global annual time series of aboveground biomass (AGB) estimated from radar satellites between 1992 and 2018, we present forest carbon changes and provide insights on their sensitivities to environmental conditions across scales. Our findings indicate differences in forest carbon changes across AGB classes, with regions with carbon stocks of 50–125 MgC ha−1 depict the highest forest carbon gains and losses, while regions with 125–150 MgC ha−1 have the lowest forest carbon gains and losses in absolute terms. Net forest carbon change estimates show that the arc‐of‐deforestation and the Congo Basin were the main hotspots of forest carbon loss, while a substantial part of European forest gained carbon during the last three decades. Furthermore, we observe that changes in forest carbon stocks were systematically positively correlated with changes in forest cover fraction. At the same time, it was not necessarily the case with other environmental variables, such as air temperature and water availability at the bivariate level. We also used a model attribution method to demonstrate that atmospheric conditions were the dominant control of forest carbon changes (56% of the total study area) followed by water‐related (29% of the total study area) and vegetation (15% of the total study area) conditions. Regionally, we find evidence that carbon gains from long‐term forest growth covary with long‐term carbon sinks inferred from atmospheric inversions. Our results describe the contributions from the atmosphere, water‐related and vegetation conditions to forest carbon changes and provide new insights into the underlying mechanisms of the coupling between forest growth and the global carbon cycle.

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“…The boreal biome occupies nearly one-third of the global forested land, and about 66% and 30% of the world's forest carbon (C) pool is stored in their soil and vegetation, respectively (Burton et al, 2003;Kasischke, 2000). Boreal forests are generally C sinks (0.5 ± 0.1 Pg C year -1 ), but they can become transient C sources due to disturbances such as fires (Pan et al, 2011;Zhao et al, 2020). Increased fire activity associated with the warming climate may lead this biome to act as a long-term regional C source, as seen in Alaska and Canada during 1986 -2016 (Zhao et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

“…Boreal forests are generally C sinks (0.5 ± 0.1 Pg C year -1 ), but they can become transient C sources due to disturbances such as fires (Pan et al, 2011;Zhao et al, 2020). Increased fire activity associated with the warming climate may lead this biome to act as a long-term regional C source, as seen in Alaska and Canada during 1986 -2016 (Zhao et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Short- to medium-term effects of crown and surface fires on soil respiration in a Canadian boreal forest

Ribeiro-Kumara¹,

Santín

Doerr

et al. 2022

Can. J. For. Res.

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Fires are an important perturbation for the carbon (C) dynamics of boreal forests, especially when they are stand-replacing. In North American boreal forests, crown fires are predominant and, therefore, the most studied. However, surface fires can also lead to major tree mortality with substantial implications for the C balance. Here, we assess the short- (hours – days) to medium-term (1 – 3 years) effects of the different fire types (surface vs. crown) on the postfire soil C effluxes in jack pine and black spruce forest stands in the Northwest Territories, Canada. We found that while trees were instantly killed by the four crown fires studied, trees also died within one year after two of three surface fires studied. Associated with this tree mortality, soil autotrophic respiration decreased after both fire types, although at different timings. The soil heterotrophic respiration was either lower or unchanged when measured 1 – 3 years after either fire type, but was increased when measured immediately after a surface fire, possibly due to the interaction between ash generation and wetting performed to suppress the fire. Our results suggest that both fire types can thus substantially alter C fluxes in the short- to medium-term, both through changes in vegetation and the soil environment.

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North American Boreal Forests Are a Large Carbon Source Due to Wildfires From 1986 to 2016

Cited by 5 publications

References 55 publications

Analyzing the Spatiotemporal Patterns of Forests Carbon Sink and Sources Between 2000 and 2019

Analyzing the Spatiotemporal Patterns of Forests Carbon Sink and Sources Between 2000 and 2019

Global sensitivities of forest carbon changes to environmental conditions

Short- to medium-term effects of crown and surface fires on soil respiration in a Canadian boreal forest

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