Abiotic and biotic drivers of microbial respiration in peat and its sensitivity to temperature change

doi:10.1016/j.soilbio.2020.108077

Soil Biology and Biochemistry

Volume 153, February 2021, 108077

https://doi.org/10.1016/j.soilbio.2020.108077 Get rights and content

Highlights

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Temperature increased respiratory activity until optimum temperature then declined.
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More decomposed peat decreased the amount of microbes but not respiratory activity.
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Q₁₀ of aerobic respiration increased by 14% at 35–40 cm than 5–10 cm peat layer.
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Depth dependent Q₁₀ in peat profile can be applied in modeling peat decomposition.

Abstract

The effect of climate change on peatlands is of great importance due to their large carbon stocks. In this study, we examined microbial biomass and effect of temperature and O₂ availability on soil respiration of surface and subsurface Sphagnum peat. The interactive effect of biotic and abiotic factors significantly affects soil respiration. Increasing temperature enhanced the microbial respiratory activity and thus the soil respiration, while there is a temperature threshold. The more decomposed subsurface peat showed a lower CO₂ production due to less labile carbon and lower microbial biomass, but a higher temperature sensitivity. Q₁₀ of aerobic respiration increased from 1.93 ± 0.26 in surface to 2.20 ± 0.01 in subsurface peat. The linear relationship between Q₁₀ and depth in the uppermost 50 cm peat section can be used to improve the estimation of CO₂ production in peat profiles.

Section snippets

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was supported by the Labex VOLTAIRE (grant No. ANR-10-LABX-100-01). This work was funded as part of the CAREX project supported by the Loire Valley Center Region and the FEDER. This study was undertaken in the framework of the French Peatland Observatory, SNO Tourbières, accredited by CNRS-INSU. We would like to thanks C. Longue for the contribution of analysis of microbial biomass, M. Hatton for the elemental analysis and Dr. J. Mora-Gomez for the helpful suggestions.

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Peatlands play an important role in global carbon cycling, as they act as a natural sink of carbon dioxide (CO₂) or as a source of methane (CH₄). The influence of microtopography (lawns and hummock-hollow complexes) in the biogeochemical dynamics of dissolved organic and inorganic carbon (DOC and DIC) and dissolved CH₄ and CO₂ is generally miss-considered. Southernmost Patagonia has huge areas of pristine peatlands, which are still in a largely natural state with scarce anthropogenic influence. In this study we provide foundational insights into the dynamics of greenhouse gasses (GHGs) and DOC in Sphagnum dominated peatlands of Southern Patagonia, assessing the impact of microtopography on these dynamics. The stocks of dissolved GHGs and DOC in hummock-hollows complex and lawns were analysed at three depths (25, 50, and 75 cm) in four ombrotrophic peatbogs. CH₄, N₂O and CO₂ fluxes, net ecosystem exchange (NEE) and gross primary productivity (GPP) were also studied. CO₂ and CH₄ fluxes were strongly affected by microtopography. Hummock-hollows showed higher CO₂ fluxes, and temperature and radiation were the main drivers for respiration and GPP, respectively. In addition, in this microtopography, higher DOC concentrations were observed at the top depth. In contrast, lawns acted as a source of CH₄, with higher emission rates and high dissolved GHGs concentration throughout the depth profile.
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The boreal forest holds the world's largest soil carbon (C) reservoir. A large portion of it is contained in a thick organic layer originating from the slow decay of bryophytes. Because a thick organic layer slows down tree growth, reduces forest productivity, and thereby reduces the potential wood supply, silvicultural treatments that aim to maintain or restore forest productivity after harvesting often involve mechanical site preparation. However, while these treatments can increase growth and C storage in trees, they can also lead to accelerated decomposition of the soil organic matter, reducing C storage. In this study, we assessed the nine-years effect of two silvicultural treatments on soil C dynamics in forested peatlands of northwestern Quebec, compared to unharvested controls: (1) cut with protection of regeneration and soils (CPRS; low soil disturbance, also called careful logging around advanced growth (CLAAG)), (2) CPRS followed by mechanical site preparation (CPRS + MSP, plowing; severe soil disturbance). The mass loss rate of three bryophytes (Pleurozium schreberi, Sphagnum capillifolium, and Sphagnum fuscum) was measured over two growing seasons together with soil organic carbon (SOC) stocks. We also studied the different effects of temperature, water table level, depth, and type of soil layer on mosses decomposition.We observed a significant influence of silvicultural treatments, bryophyte species, and soil layer type (fibric, mesic, humic and mineral) on bryophyte mass loss, which was higher in the CPRS + MSP treatment (21.6 ± 0.13 % standard error) than in control sites (9.5 ± 0.21 %); CPRS alone resulted in an intermediate mass loss of 11.6 ± 0.23 %, for Sphagnum mosses. Bryophyte mass loss was significantly higher in fibric than humic layer. SOC stocks in the uppermost organic soil layer (fibric) were lower in the CPRS + MSP group than in the control group, while the CPRS group was intermediate; however, differences were not statistically significant for the other soil layer and for total SOC. We conclude that while CPRS + MSP accelerates Sphagnum moss decomposition in the topsoil layer, it has limited impact on total soil C stocks that are detectable with stock change methods.
Divergent pattern of soil CO<inf>2,</inf> CH<inf>4</inf> and N<inf>2</inf>O emissions in 18-year citrus orchard and Camellia oleifera plantations converted from natural shrub forests
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Citation Excerpt :
Moreover, our previous study in this area showed that the application of nitrogen fertilizers significantly reduced soil microbial biomass and the abundance of nitrifiers and denitrifiers in the 18-years-old plantations in contrast to organic amendments, which can hinder the production and emission of soil N2O (Chen et al., 2012; Chen et al., 2010). In this study, seasonal variations in soil CO2 emission were found in the two plantations, and the highest rates and cumulative emissions of CO2 were observed summer, and the lowest rates were observed in winter (Figs. 2d, 4b) mainly because enzymatic and microbial activities were promoted by increase in temperature in summer and subsequent increased in the respiration in the roots and microorganisms (Li et al., 2021b; Wu, 2020). These seasonal variations were consistent with those observed in other studies (Davidson and Janssens, 2006; Munjonji et al., 2021; Tang et al., 2006).
A large number of natural shrub forests were converted to oil plants and orchards in the subtropical area of China for economic reasons, but the ecological consequences such as greenhouse gas (GHG) flux, remains unclear. The objectives were to explore how environmental factors, including seasonal and inter-annual variations, and management factors are affecting the GHG fluxes. The study was performed in 18-years-old plantations in a subtropical hilly region in south China. Methane (CH₄), nitrous oxide (N₂O), and carbon dioxide (CO₂) fluxes were continuously measured using a manual static chamber technology at a citrus orchard and Camellia oleifera plantation. Results showed that fluxes of CH₄, N₂O, and CO₂ fluxes were strongly affected by the two plantations, and CH₄ uptake and CO₂ emission rate at the C.oleifera plantation were higher than those in the citrus orchard site mainly due to the high soil temperature and soil organic carbon contents in C.oleifera systems. The citrus orchard had higher annual N₂O emission than the C.oleifera plantation. One of the reasons was N fertilizers were applied to the orchard, as indicated by increase in NO₃⁻-N content and the positive correlation between N₂O emissions and soil NO₃⁻-N. Overall, the global warming potential (GWP) was significantly higher in C.oleifera plantation than that in the citrus orchard (579.11 ± 17.06 vs. 418.13 ± 17.19 kg CO_2eq ha⁻¹ yr⁻¹). The range of annual cumulative fluxes measured from the citrus orchard and C.oleifera ecosystems were – (78.88–92.42) g CH₄–C ha⁻¹ yr⁻¹, 89.3–124.75 g N₂O-N ha⁻¹ yr⁻¹, and 389.58–563.56 kg CO₂-C ha⁻¹ yr⁻¹. The amount of GHG emitted in summer was 1.5–6.6 times higher than the sum of the other three seasons, indicating that CO₂ may be emitted from soil in cool seasons when temperature continues to increase due to global warming. Notably, the continuous increase in the use of fertilizers in economic forests in subtropical hilly regions might increase N₂O emissions, which may offset the net climate benefits of increasing carbon sequestration by plants.
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Citation Excerpt :
They postulated that these abiotically-driven decomposition pathways contributed almost equally as biotic pathways to CO2 production. Despite the growing numbers of studies in recent years that investigate the coupled biotic and abiotic degradation in terrestrial ecosystems (Choudhary et al., 2018; Fudyma et al., 2021a,b; Juan-Ovejero et al., 2020; Li et al., 2021), current climate models still fail to capture and integrate the coupled biotic and abiotic controls on SOM degradation. Peatlands are globally important stores of organic carbon (OC).
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Short CommunicationAbiotic and biotic drivers of microbial respiration in peat and its sensitivity to temperature change

Highlights

Abstract

Section snippets

Declaration of competing interest

Acknowledgements

Soil Biology and Biochemistry

Soil Biology and Biochemistry

Soil Biology and Biochemistry

Soil Biology and Biochemistry

Organic Geochemistry

Soil Biology and Biochemistry

Journal of Environmental Sciences

Comparison of different methods to determine the degree of peat decomposition in peat bogs

Biogeosciences

Halogens in pore water of peat bogs – the role of peat decomposition and dissolved organic matter

Biogeosciences

Peat decomposition records in three pristine ombrotrophic bogs in southern Patagonia

Biogeosciences

Sensitivity of organic matter decomposition to warming varies with its quality

Global Change Biology

Experimental warming shows that decomposition temperature sensitivity increases with soil organic matter recalcitrance

Ecology

Temperature sensitivity of soil carbon decomposition and feedbacks to climate change

Nature

Short Communication
Abiotic and biotic drivers of microbial respiration in peat and its sensitivity to temperature change