Pyrogenic Carbon Generation From Fire and Forest Restoration Treatments

DeLuca, Thomas H.; Gundale, Michael J.; Brimmer, Rachel; Gao, Si

doi:10.3389/ffgc.2020.00024

Cited by 18 publications

(8 citation statements)

References 45 publications

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“…In support of our first hypothesis, PyC concentration in mineral soils of the two stands surveyed was spatially autocorrelated only at fine scales <0.5 m. Prior broad-scale surveys have reported wide-ranging mass-based concentrations of recalcitrant organic charcoals in coniferous and boreal forests from 1% to 20% (Forbes et al, 2006;Lynch et al, 2004); the most common range reported being 1%-5% (Deluca et al, 2020;Preston & Schmidt, 2006). Herein, mass-based concentrations of PyC of samples soils ranged widely 0.2%-40% with an average of 15%, corresponding to a mean of 109 (range 0-276) t/ha.…”

Section: Discussionsupporting

confidence: 73%

Spatial heterogeneity in soil pyrogenic carbon mediates tree growth and physiology following wildfire

Gale

Thomas

2020

Journal of Ecology

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1. Pyrogenic carbon (PyC) is a ubiquitous legacy of wildfire in terrestrial soils, yet how it affects the growth and function of regenerating plants has received little research attention. 2. We examined responses to a natural gradient of PyC deposition 5 years following a severe fire in a northern boreal forest, based on measurements of growth (height, basal area increment and leader extension), physiological performance (Fv/Fm) and foliar nutrition (C, N, P, K, Mg) of Pinus banksiana Lamb. We determined the concentration of PyC, expressed as a dosage (t/ha, in mineral soils collected from the rootzones of each sapling and used it as an independent factor to model trait responses to increasing PyC levels, in conjunction with measurements of soil physio-chemical properties (pH, EC, VOC, Ash, N, P, K, Ca and Mg). 3. Quantification and spatial analysis of PyC reveals heterogeneous deposition across the landscape with fine-grained patchiness at scales <0.5 m. In response to this heterogeneity, phenotypic and nutritional adjustments followed dose-dependent response patterns. Beneficial effects of PyC on sapling growth occurred to an optimum point of ~30-60 t/ha, while declining patterns were found for trees in dosages exceeding 100 t/ha. Some traits were positively and negatively related to soil K and N, respectively, and shared strong negative associations with soil pH and volatile matter. 4. Synthesis. This study supports the longstanding hypothesis that soil PyC enhances growth and physiological function of fire-adapted plants, but indicates that responses are highly dosage-dependent, with natural levels of PyC deposition commonly exceeding an optimum point. These results also suggest that the main mechanisms for observed responses to PyC include: (a) enhanced supply of base cations, (b) immobilization of N and (c) pronounced liming. Future changes in climate are expected to increase fire frequency, particularly in circumpolar boreal forests. We predict shifts in PyC to frequently exceed the threshold resulting in reduced plant growth and ultimately ecosystem productivity.

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Section: Discussionsupporting

confidence: 73%

Spatial heterogeneity in soil pyrogenic carbon mediates tree growth and physiology following wildfire

Gale

Thomas

2020

Journal of Ecology

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“…This may be because incomplete burning of soil organic matter occurs during forest fires, which leads to the formation of pyromorphic humus and/or charcoal; these are both highly resistant to oxidation and provide a poor resource for soil organisms (González‐Pérez et al ., 2004). Moreover, stable pyrogenic C (charcoal) deposited in soil can lead to the loss of humus in forest soils (Wardle et al ., 2008) likely because it may adsorb organic compounds in plant root exudates, litter decomposition products and microbial byproducts (DeLuca et al ., 2020).…”

Section: Discussionmentioning

confidence: 99%

Forest fire induces short‐term shifts in soil food webs with consequences for carbon cycling

et al. 2020

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We tested for fire‐induced (5–6 years post‐fire) changes in the structure and functioning of the soil food web along a 3000‐km north–south transect across European Russia, spanning all major forest types in the northern hemisphere outside the tropics. The total biomass of the detrital food web, including microbes and invertebrates, was not affected by fire. However, fire reduced the biomass of microfauna and mites, but had no impact on mesofauna or macrofauna. Fire also reduced rates of carbon (C) mobilisation by soil biota. Our results demonstrate that fire‐induced shifts in soil food webs have significant short‐term effects on forest soil C cycling, but that these effects vary across forest types and geographic locations.

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“…Santín et al (2015) found 480 g m −2 formed during a wildfire in a Canadian boreal forest of jack pine in the canopy, DW, and forest floor components combined. DeLuca et al (2020) recorded a PyC production of 224 g m −2 in the forest floor component during a prescribed fire in a thinned ponderosa pine forest in Montana. These rates of PyC productions during wildfire are of the order of 2–19 times greater than the values observed in the experimental mixed fuel beds investigated here (25–166 g m −2 , Table S2).…”

Section: Discussionmentioning

confidence: 99%

The Relevance of Pyrogenic Carbon for Carbon Budgets From Fires: Insights From the FIREX Experiment

Santín

Doerr

Jones

et al. 2020

Global Biogeochemical Cycles

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Vegetation fires play an important role in global and regional carbon cycles. Due to climate warming and land use shifts, fire patterns are changing and fire impacts increasing in many of the world's regions. Reducing uncertainties in carbon budgeting calculations from fires is therefore fundamental to advance our current understanding and forecasting capabilities. Here we study 20 chamber burns from the FIREX FireLab experiment, which burnt a representative set of North American wildland fuels, to assess the following: (i) differences in carbon emission estimations between the commonly used "consumed biomass" approach and the "burnt carbon" approach; (ii) pyrogenic carbon (PyC) production rates; and (iii) thermal and chemical recalcitrance of the PyC produced, as proxies of its biogeochemical stability. We find that the "consumed biomass" approach leads to overestimation of carbon emissions by 2-27% (most values between 2% and 10%). This accounting error arises largely from not considering PyC production and, even if relatively small, can therefore have important implications for medium-and long-term carbon budgeting. A large fraction (34-100%) of this PyC was contained in the charred fine residue, a postfire material frequently overlooked in fire carbon research. However, the most recalcitrant PyC was in the form of woody charcoal, with estimated half-lives for most samples exceeding 1,000 years. Combustion efficiency was relatively high in these laboratory burns compared to actual wildland fire conditions, likely leading to lower PyC production rates. We therefore argue that the PyC production values obtained here, and associated overestimation of carbon emissions, should be taken as low-end estimates for wildland fire conditions. Plain Language Summary Wildfires release substantial amounts of carbon into the atmosphere with direct implications for climate change and air quality. However, not all the carbon from the burnt vegetation is emitted; a fraction of it remains on the ground as charcoal (pyrogenic carbon-PyC). PyC is more resistant to degradation than unburnt vegetation, and the carbon it contains can be stored in soils and sediments for long periods of time instead of going back to the atmosphere. Most current carbon emissions estimations do not take PyC production into account and assume that all carbon burnt is emitted into the atmosphere. Here we quantify carbon emissions and PyC production during the FIREX laboratory burns (Missoula Fire Lab, October 2016), where a range of North American vegetation types (e.g., chaparral shrubs, conifer trees) were burnt to study their emissions. We found that the current way of calculating carbon emissions can lead to an overestimation of carbon emissions of between 2% and 27%. We also found that the PyC produced during burning is mostly held not in big woody pieces of charcoal but instead in small charred particles, which are often not accounted for in wildfire research.

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Pyrogenic Carbon Generation From Fire and Forest Restoration Treatments

Cited by 18 publications

References 45 publications

Spatial heterogeneity in soil pyrogenic carbon mediates tree growth and physiology following wildfire

Spatial heterogeneity in soil pyrogenic carbon mediates tree growth and physiology following wildfire

Forest fire induces short‐term shifts in soil food webs with consequences for carbon cycling

The Relevance of Pyrogenic Carbon for Carbon Budgets From Fires: Insights From the FIREX Experiment

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