Comparison of carbon dynamics and water use efficiency following fire and harvesting in Canadian boreal forests

Mkhabela, M.S.; Amiro, B.D.; Barr, Alan G.; Black, T. Andrew; Hawthorne, I.; Kidston, Joseph; McCaughey, J. H.; Orchansky, Alberto L.; Nesic, Zoran; Sass, Alison; Shashkov, A. A.; Zha, Tianshan

doi:10.1016/j.agrformet.2008.10.025

Cited by 111 publications

(78 citation statements)

References 58 publications

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“…The built-in IRGA diagnostic signal was used to identify unreliable data due to obstruction of the IRGA's path. Nighttime (defined as incoming shortwave radiation \10 W m -2 ) CO 2 flux data were rejected when friction velocity (u * ) was below the threshold value of 0.08 m s -1 ; determined using the technique described in Mkhabela et al (2009). This threshold was also corroborated through visual inspection by plotting nighttime F c against u * and identifying the u * value beyond which u * and CO 2 fluxes are no longer related.…”

Section: Instrumentation and Flux Calculationsmentioning

confidence: 78%

“…Users of open-path IRGAs (LI-7500) have reported occasional CO 2 uptake during the cold season, when photosynthesis is improbable (Amiro 2010;Hirata et al 2007;Lafleur and Humphreys 2008;Mkhabela et al 2009). This problem has been attributed to the surface heating of the IRGA body by the electronics, which generates an additional sensible heat flux (Burba et al 2008;Grelle and Burba 2007).…”

Section: Instrumentation and Flux Calculationsmentioning

confidence: 99%

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Inter-annual variability in water table depth controls net ecosystem carbon dioxide exchange in a boreal bog

2015

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The net ecosystem carbon dioxide (CO 2 ) exchange (NEE) between boreal bogs and the atmosphere and its environmental drivers remains understudied despite the large carbon store of these northern ecosystems. We present NEE measurements using the eddy covariance technique in a boreal ombrotrophic bog over five growing seasons and four winters. Interannual variability in CO 2 uptake was most pronounced in June-September (-4 to -122 g CO 2 -C m -2 ), less in March-May (-1 to -21 g CO 2 -C m -2 ) and very small in October-November (-2 to -4 g CO 2 -C m -2 ). Variability in NEE between years was linked primarily to changes in water table depth (WTD). Strong and significant relationships (r 2 [ 0.89, p B 0.05) were found between summer (JuneSeptember) maximum photosynthetic rate (A max ), net ecosystem productivity (NEP), gross ecosystem productivity and WTD. Adding air temperature through multiple regression analysis further increased correlation between summer A max , NEP, and WTD (r 2 = 0.96, p = 0.05). In contrast to previous studies examining controls on peatland CO 2 exchange, no relationships were found between productivity or cumulative exchange and early season temperature, timing of the snowmelt or growing season length.

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Section: Instrumentation and Flux Calculationsmentioning

confidence: 78%

Section: Instrumentation and Flux Calculationsmentioning

confidence: 99%

Inter-annual variability in water table depth controls net ecosystem carbon dioxide exchange in a boreal bog

2015

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“…[29] We used the areal coverage of each type of aquatic system within the pre-flood basin ( [Blais et al, 2005;Amiro et al, 2006;Barr et al, 2007;Yuan et al, 2008;Mkhabela et al, 2009]. The range of NEE for the wetland components was similar to that of the forest, in the order of À218 to 14.2 mg C m…”

Section: Pre-flood Fluxesmentioning

confidence: 99%

“…For deciduous forests, the CO 2 budget was derived from literature data on eddy covariance NEE measurements made in boreal aspen forests [Arain et al, 2002;Amiro et al, 2006;Barr et al, 2007]. Literature data from similar regions were also used to estimate the CO 2 budget for burned forests of different ages [Amiro et al, 2006;Mkhabela et al, 2009]. Since it is recognized that the forest fire cycle in this region is around 100 years [Bergeron et al, 2004], we assumed that about 1% of the total area (coniferous + deciduous + previously burnt), would burn every year, and that 50% of the related biomass (but not soil carbon) burned would be emitted to the atmosphere as CO 2 .…”

Section: Forestsmentioning

confidence: 99%

The net carbon footprint of a newly created boreal hydroelectric reservoir

Teodoru

Bastien

Bonneville

et al. 2012

Global Biogeochemical Cycles

137

102

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[1] We present here the first comprehensive assessment of the carbon (C) footprint associated with the creation of a boreal hydroelectric reservoir (Eastmain-1 in northern Québec, Canada). This is the result of a large-scale, interdisciplinary study that spanned over a 7-years period (2003)(2004)(2005)(2006)(2007)(2008)(2009)), where we quantified the major C gas (CO 2 and CH 4 ) sources and sinks of the terrestrial and aquatic components of the pre-flood landscape, and also for the reservoir following the impoundment in 2006. The pre-flood landscape was roughly neutral in terms of C, and the balance between pre-and post-flood C sources/sinks indicates that the reservoir was initially (first year post-flood in 2006) a large net source of CO 2 (2270 mg C m À2 d À1) but a much smaller source of CH 4 (0.2 mg C m À2 d À1). While net CO 2 emissions declined steeply in subsequent years (down to 835 mg C m À2 d À1 in 2009), net CH 4 emissions remained constant or increased slightly relative to pre-flood emissions. Our results also suggest that the reservoir will continue to emit carbon gas over the long-term at rates exceeding the carbon footprint of the pre-flood landscape, although the sources of C supporting these emissions have yet to be determined. Extrapolation of these empirical trends over the projected life span (100 years) of the reservoir yields integrated long-term net C emissions per energy generation well below the range of the natural-gas combined-cycle, which is considered the current industry standard.

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“…However, this is uncertain given the concurrently increasing proportion of young forests in the landscape. The post-harvesting NEP-age relationship may also differ from that deduced from analysis of post-fire data (Mkhabela et al 2009, Amiro et al 2010, making the evaluation of the effects of harvesting practices on NEP even more challenging.…”

mentioning

confidence: 98%

Increasing potential NEP of eastern boreal North American forests constrained by decreasing wildfire activity

2011

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Abstract. Wildfire activity has been decreasing over the past few centuries across North America's southeastern boreal forest. This change has caused a gradual shift in the age-class distribution toward a stronger representation of old-growth stands (age . 140 years) in unmanaged forest landscapes. Parallel to these changes, there has been an improvement in growth conditions driven by climate warming. Given the negative feedback of forest aging on net ecosystem production (NEP), a reasonable case can be made about an age-effect constraint on a climate change-induced increase in carbon assimilation. Here we combine empirical information (multicentury tree-ring records, time-since-fire map, and forest inventories) along with model simulations to develop a reconstruction of NEP of jack pine forests (Pinus banksiana Lambert) at the transition zone of the Spruce-feather moss and Balsam fir-white birch bioclimatic domains of eastern boreal North America covering the period A.D. 1830 to 1999. From this reconstruction, we test the hypothesis that currently improving carbon assimilation in unmanaged forests due to climate change is being offset by the aging of the forests resulting from the decreasing activity of wildfires. A sensitivity analysis of results to different assumptions about the carbon sink strength of old-growth forests is also made via a probability distribution derived from 10,000 ensemble members. Our simulation results suggest that increasing moisture availability and lengthening of the growing season contributed to a statistically significant upward trend in carbon assimilation of 0.39 g C m À2 yr À1 over 1901-2009. Meanwhile, mean age of jack pine stands has also changed, shifting from 87 years in the 1920s to 131 years in 1999. This forest aging contributed up to a 12% reduction in carbon assimilation from the 1930s to 1990s, an effect that is found to be sufficient to offset NEP increases due to climate change in 75% of our ensemble members. Great caution should therefore be applied when interpreting future carbon assimilation or forest growth projections that do not account for such second-order feedback from disturbances.

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Comparison of carbon dynamics and water use efficiency following fire and harvesting in Canadian boreal forests

Cited by 111 publications

References 58 publications

Inter-annual variability in water table depth controls net ecosystem carbon dioxide exchange in a boreal bog

Inter-annual variability in water table depth controls net ecosystem carbon dioxide exchange in a boreal bog

The net carbon footprint of a newly created boreal hydroelectric reservoir

Increasing potential NEP of eastern boreal North American forests constrained by decreasing wildfire activity

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