Carbon emissions from fires in permafrost peatlands

Increases in arctic and boreal fires can switch these biomes from a long-term carbon (C) sink to a source through direct fire emissions and longer-term emissions from soil respiration. Landscapes of intermediate drainage tend to experience the highest C combustion, dominated by soil C emissions, because of relatively thick and periodically dry organic soils. These landscapes may also induce a climate warming feedback through combustion and post-fire respiration of legacy C &#8211; soil C that had escaped burning in the previous fire &#8211; including from permafrost thaw and degradation. Data shortages from fires in tundra ecosystems and Eurasian boreal forests limit our understanding of C emissions from arctic-boreal fires. Interactions between fire, topography, vegetation, soil and permafrost need to be considered when estimating climate feedbacks of arctic-boreal fires.

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Carbon loss from boreal forest wildfires offset by increased dominance of deciduous trees

Science ◽

10.1126/science.abf3903 ◽

2021 ◽

Vol 372 (6539) ◽

pp. 280-283

Author(s):

Michelle C. Mack ◽

Xanthe J. Walker ◽

Jill F. Johnstone ◽

Heather D. Alexander ◽

April M. Melvin ◽

...

Keyword(s):

Carbon Storage ◽

Climate Warming ◽

Boreal Forests ◽

Black Spruce ◽

Organic Soils ◽

Deciduous Trees ◽

Ecological Change ◽

Dominant Plant Species ◽

Slow Growing

In boreal forests, climate warming is shifting the wildfire disturbance regime to more frequent fires that burn more deeply into organic soils, releasing sequestered carbon to the atmosphere. To understand the destabilization of carbon storage, it is necessary to consider these effects in the context of long-term ecological change. In Alaskan boreal forests, we found that shifts in dominant plant species catalyzed by severe fire compensated for greater combustion of soil carbon over decadal time scales. Severe burning of organic soils shifted tree dominance from slow-growing black spruce to fast-growing deciduous broadleaf trees, resulting in a net increase in carbon storage by a factor of 5 over the disturbance cycle. Reduced fire activity in future deciduous-dominated boreal forests could increase the tenure of this carbon on the landscape, thereby mitigating the feedback to climate warming.

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Nonnegligible role of warming-induced soil drying in regulating warming effect on soil respiration

10.1101/273573 ◽

2018 ◽

Author(s):

Enzai Du

Keyword(s):

Soil Respiration ◽

Annual Variation ◽

Precipitation Anomaly ◽

Soil Drying ◽

Phase Pattern ◽

Soil Warming ◽

Soil C ◽

C Dynamics

AbstractBased on results of a 26-year soil warming experiment (soil temperature being elevated by 5 °C) in a Harvard hardwood forest, Melillo et al. demonstrated a four-phase pattern of long-term warming effect on soil respiration, while the mechanisms were not fully elucidated because they neglected the indirect effect due to warming-induced soil drying. By showing a significant correlation between precipitation anomaly and inter-annual variation of warming effect on soil respiration, we suggest a nonnegligible role of warming-induced soil drying in regulating the long-term warming effect on soil respiration. Our analysis recommends further efforts to consider both the direct and indirect (i.e., warming-induced soil drying) warming effects to gain more in-depth understanding of the long-term soil C dynamics.

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Soil carbon loss in warmed subarctic grasslands is rapid and restricted to topsoil

10.5194/bg-2021-338 ◽

2022 ◽

Author(s):

Niel Verbrigghe ◽

Niki I. W. Leblans ◽

Bjarni D. Sigurdsson ◽

Sara Vicca ◽

Chao Fang ◽

...

Keyword(s):

Soil Carbon ◽

Critical Role ◽

Aggregate Size ◽

Climate Feedbacks ◽

Soil Warming ◽

Soil C ◽

Soc Stock ◽

Mate System ◽

Soc Stocks

Abstract. Global warming may lead to carbon transfers from soils to the atmosphere, yet this positive feedback to the cli- mate system remains highly uncertain, especially in subsoils (Ilyina and Friedlingstein, 2016; Shi et al., 2018). Using natural geothermal soil warming gradients of up to +6.4 °C in subarctic grasslands (Sigurdsson et al., 2016), we show that soil organic carbon (SOC) stocks decline strongly and linearly with warming (−2.8 ton ha−1 °C−1). Comparison of SOC stock changes following medium-term (5 and 10 years) and long-term (> 50 years) warming revealed that all SOC loss occurred within the first five years of warming, after which continued warming no longer reduced SOC stocks. This rapid equilibration of SOC observed in Andosol suggests a critical role for ecosystem adaptations to warming and could imply short-lived soil carbon-climate feedbacks. Our data further revealed that the soil C loss occurred in all aggregate size fractions, and that SOC losses only occurred in topsoil (0–10 cm). SOC stocks in subsoil (10–30 cm), where plant roots were absent, remained unaltered, even after > 50 years of warming. The observed depth-dependent warming responses indicate that explicit vertical resolution is a prerequisite for global models to accurately project future SOC stocks for this soil type and should be investigated for soils with other mineralogies.

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Spatial heterogeneity of temperature sensitivity of soil respiration across China

10.5194/ismc2021-42 ◽

2021 ◽

Author(s):

Zhihan Yang ◽

Xiaolu Tang ◽

Xinrui Luo ◽

Yuehong Shi

Keyword(s):

Soil Respiration ◽

Soil Carbon ◽

Temperature Sensitivity ◽

Terrestrial Ecosystems ◽

Mean Value ◽

Field Observations ◽

Climate Feedbacks ◽

Tropical Areas ◽

Model Efficiency

Soil respiration (RS), consisting of soil autotrophic respiration (RA) and heterotrophic respiration (RH), is the largest outflux of CO2 from terrestrial ecosystems to the atmosphere. The temperature sensitivity (Q10) of RS is a crucial role in benchmarking the intensity of terrestrial soil carbon-climate feedbacks. However, the heterogeneity of Q10 of RS has not been well explored. To fill this substantial knowledge gap, gridded long-term Q10 datasets of RS at 5 cm with a spatial resolution of 1 km were developed from 515 field observations using a random forest algorithm with the linkage of climate, soil and vegetation variables. Q10 of RA and RH were estimated based on the linear correlation between Q10 of RS and RA/RH. Field observations indicated that regardless of ecosystem types, Q10 of RS ranged from 1.54 to 4.17 with an average of 2.52. Q10 varied significantly among ecosystem types, with the highest mean value of 3.18 for shrubland, followed by wetland (2.66), grassland (2.49) and forest (2.48), whereas the lowest value of 2.14 was found in cropland. RF could well explain the spatial variability of Q10 of RS (model efficiency = 0.5). Temporally, Q10 of RS, RA and RH did not differ significantly (p = 0.386). Spatially, Q10 of RS, RA and RH varied greatly. In different climatic zones, the plateau areas had the highest mean Q10 value of 2.88, followed by tropical areas (2.63), temperate areas (2.52), while the subtropical region had the lowest Q10 on average (2.37). The predicted mean Q10 of RS, RA and RH were 2.52, 2.29, 2.64, respectively, with strong spatial patterns, indicating that the traditional and constant Q10 of 2 may bring great uncertainties in understanding of soil carbon-climate feedbacks in a warming climate.

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Effects of long-term nitrogen addition on soil respiration and its components in a boreal forest

10.21203/rs.3.rs-57463/v1 ◽

2020 ◽

Author(s):

Guancheng Liu ◽

Tong Liu ◽

Guoyong Yan ◽

Lei Wang ◽

Xiaochun Wang ◽

...

Keyword(s):

Soil Respiration ◽

Boreal Forest ◽

Forest Ecosystems ◽

Nitrogen Addition ◽

N Deposition ◽

Microbial Biomass C ◽

N Addition ◽

Soil C ◽

C And N

Abstract Background Atmospheric nitrogen (N) deposition in boreal forest ecosystems increased gradually with the development of industry and agriculture, but the effects of N input on soil CO2 fluxes in these ecosystems were rarely reported in previous studies. To evaluate the effect of N addition on soil respiration is of great significance for understanding the distribution of soil carbon (C) on the N gradient in forest ecosystems.Results In this study, four treatment levels of N addition (0, 25, 50, 75 kg N ha− 1 yr− 1) were applied to natural Larix gmelinii forest in Greater Khingan Mountains of northeast China. We focused mainly on the dynamics of soil respiration (Rs), heterotrophic respiration (Rh), autotrophic respiration (Ra), microbial biomass C and N (MBC and MBN) and fine root biomass (FRB) in a growing season. We found that low N addition significant increased Rs, Rh and Ra, but with the increase of N addition, the promotion effect was gradually weakened. Medium N increased the temperature sensitivity (Q10) of Rs and Rh components, while medium N and high N significantly reduced the Q10 of Ra. Ra was positively correlated with FRB; Rh was positively correlated with soil MBC and MBN; and RS was probably driven by Ra from May to July, while by Rh in August and September.Conclusions Long-term N addition alleviated microbial N limitation, promoted soil respiration and accelerated soil C and N cycle in boreal forest ecosystems.

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Climate Warming and Long-Term Trends in Saskatchewan Hay Yield

Modern Environmental Science and Engineering ◽

10.15341/mese(2333-2581)/12.02.2016/001 ◽

2016 ◽

Vol 2 (12) ◽

pp. 765-768 ◽

Cited By ~ 1

Author(s):

Paul G. Jefferson

Keyword(s):

Climate Warming ◽

Long Term Trends

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Enhanced Seasonal Exchange of CO2 by Northern Ecosystems Since 1960

Science ◽

10.1126/science.1239207 ◽

2013 ◽

Vol 341 (6150) ◽

pp. 1085-1089 ◽

Cited By ~ 221

Author(s):

H. D. Graven ◽

R. F. Keeling ◽

S. C. Piper ◽

P. K. Patra ◽

B. B. Stephens ◽

...

Keyword(s):

Boreal Forests ◽

Atmospheric Carbon Dioxide ◽

Ecosystem Models ◽

The North ◽

Ecological Changes ◽

Term Change ◽

Major Shift ◽

Underlying Mechanisms ◽

Global Carbon

Seasonal variations of atmospheric carbon dioxide (CO2) in the Northern Hemisphere have increased since the 1950s, but sparse observations have prevented a clear assessment of the patterns of long-term change and the underlying mechanisms. We compare recent aircraft-based observations of CO2 above the North Pacific and Arctic Oceans to earlier data from 1958 to 1961 and find that the seasonal amplitude at altitudes of 3 to 6 km increased by 50% for 45° to 90°N but by less than 25% for 10° to 45°N. An increase of 30 to 60% in the seasonal exchange of CO2 by northern extratropical land ecosystems, focused on boreal forests, is implicated, substantially more than simulated by current land ecosystem models. The observations appear to signal large ecological changes in northern forests and a major shift in the global carbon cycle.

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