Influence of climate change factors on carbon dynamics in northern forested peatlands

Peatlands are carbon-accumulating wetland ecosystems, developed through an imbalance among organic matter production and decomposition processes. Soil saturation is the principal cause of anoxic conditions that constrain organic matter decay. Accordingly, changes in the hydrologic regime will affect the carbon (C) dynamics in forested peatlands. Our objective is to review ecological studies and experiments on managed peatlands that provide a basis for assessing the effects of an altered hydrology on C dynamics. We conclude that climate change influences will be mediated primarily through the hydrologic cycle. A lower water table resulting from altered precipitation patterns and increased atmospheric temperature may be expected to decrease soil CH4 and increase CO2 emissions from the peat surface. Correspondingly, the C balance in forested peatlands is also sensitive to management and restoration prescriptions. Increases in soil CO2 efflux do not necessarily equate with net losses from the soil C pool. While the fundamentals of the C balance in peatlands are well-established, the combined affects of global change stressors and management practices are best considered using process-based biogeochemical models. Long-term studies are needed both for validation and to provide a framework for longitudinal assessments of the peatland C cycle. Key words: Peatland, carbon cycle, methane, forest, wetland.

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Characterization of Soil Organic Matter along an elevation gradient at Stelvio Pass (Italian Alps).

10.5194/egusphere-egu2020-10750 ◽

2020 ◽

Author(s):

Roberta Zangrando ◽

Maria del Carmen Villoslada Hidalgo ◽

Clara Turetta ◽

Nicoletta Cannone ◽

Francesco Malfasi ◽

...

Keyword(s):

Climate Change ◽

Organic Matter ◽

Soil Organic Matter ◽

Organic Carbon ◽

Elevation Gradient ◽

Total Carbon ◽

Plant Component ◽

Soil C ◽

C Cycle ◽

C Stocks

Climate Change (CC) has evident impacts on the biotic and abiotic components of ecosystems.Soil is the third largest reservoir of carbon, next to the lithosphere and the oceans, and stores approximately 1500 Gt in the top1 m depth. &#160;Even small changes in soil C stocks could have a vast impact on atmospheric CO2 concentration. Elevated surface temperature can substantially affect global C budgets and produce positive or negative feedbacks to climate change. Therefore, understanding the response of soil organic carbon (SOC) stocks to warming is of critical importance to evaluate the feedbacks between terrestrial C cycle and climate change.In comparison to other ecosystems, the areas at high altitudes and latitudes are the most vulnerable. In permafrost areas of the Northern Hemisphere the CC has already determined an increase in greenhouse gas emissions, shrub vegetation and variation in the composition of microbial communities. While numerous studies have been performed in Arctic, much less numerous are available for high altitude areas. These areas are a quarter of the emerged lands &#160;and have suffered strong impacts from the CC. Mountain permafrost makes up 14% of global permafrost, stores large quantities of organic carbon (SOC), and can release large quantities of CO2 due to climate change. However, permafrost contribution to the IPCC global budget has not yet been correctly quantified, in particular for ecosystems of prairie and shrubland, which alone could incorporate over 80Pg of C between soil and biomass. In the last decades, the plant component has undergone migration of species to higher altitudes, expansion of shrubs, variations in floristic composition and dominance, variations in area distribution. The expansion of the shrubs accelerates the regression of alpine meadows and snow valleys.The sampling activities have been carried out in July and September, from September 2017 to July 2019 in an area near Stelvio Pass (2,758 m a.s.l.) (Italian Central-Eastern Alps) along an altitude gradient. &#160;&#160;Two sampling sites located at 2600 m a.s.l. and 2200 m a.s.l. in altitude, corresponding to about 3&#176; C difference in the average annual air temperature were chosen. At the 2600 m site, warming experiments using open-top chambers (OTCs) to investigate how climate warming affects SOC were performed.In order to characterize the SOM (Soil Organic Matter), Total carbon (TC), Organic carbon (OC), Total Nitrogen (TN) and Dissolved Organic Carbon (DOC) were determined in soils. TC and TN were determined in biomass. In both soils and biomass were analyzed to quantify the distribution of stable isotopes of C and N, &#948;13C and &#948;15N.

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Post-thinning soil organic matter evolution and soil CO2 effluxes in temperate radiata pine plantations: impacts of moderate thinning regimes on the forest C cycle

Canadian Journal of Forest Research ◽

10.1139/x2012-137 ◽

2012 ◽

Vol 42 (11) ◽

pp. 1953-1964 ◽

Cited By ~ 4

Author(s):

Irene Fernandez ◽

Juan Gabriel Álvarez-González ◽

Beatríz Carrasco ◽

Ana Daría Ruíz-González ◽

Ana Cabaneiro

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Radiata Pine ◽

Soil Samples ◽

Mitigation Strategies ◽

Change Scenario ◽

Soil C ◽

C Storage ◽

C Cycle ◽

C And N

Forest ecosystems can act as C sinks, thus absorbing a high percentage of atmospheric CO2. Appropriate silvicultural regimes can therefore be applied as useful tools in climate change mitigation strategies. The present study analyzed the temporal changes in the effects of thinning on soil organic matter (SOM) dynamics and on soil CO2 emissions in radiata pine ( Pinus radiata D. Don) forests. Soil C effluxes were monitored over a period of 2 years in thinned and unthinned plots. In addition, soil samples from the plots were analyzed by solid-state 13C-NMR to determine the post-thinning SOM composition and fresh soil samples were incubated under laboratory conditions to determine their biodegradability. The results indicate that the potential soil C mineralization largely depends on the proportion of alkyl-C and N-alkyl-C functional groups in the SOM and on the microbial accessibility of the recalcitrant organic pool. Soil CO2 effluxes varied widely between seasons and increased exponentially with soil heating. Thinning led to decreased soil respiration and attenuation of the seasonal fluctuations. These effects were observed for up to 20 months after thinning, although they disappeared thereafter. Thus, moderate thinning caused enduring changes to the SOM composition and appeared to have temporary effects on the C storage capacity of forest soils, which is a critical aspect under the current climatic change scenario.

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Effects of climate change on soil organic matter chemical composition and carbon content in different physical fractions

10.5194/egusphere-egu21-9216 ◽

2021 ◽

Author(s):

Moritz Mohrlok ◽

Victoria Martin ◽

Alberto Canarini ◽

Wolfgang Wanek ◽

Michael Bahn ◽

...

Keyword(s):

Climate Change ◽

Organic Matter ◽

Chemical Composition ◽

Soil Organic Matter ◽

Soil C ◽

Size Classes ◽

Soil Fractions ◽

Total Soil ◽

C And N ◽

Amp Clay

Soil organic matter (SOM) is composed of many pools with different properties (e.g. turnover times) which are generally used in biogeochemical models to predict carbon (C) dynamics. Physical fractionation methods are applied to isolate soil fractions that correspond to these pools. This allows the characterisation of chemical composition and C content of these fractions. There is still a lack of knowledge on how these individual fractions are affected by different climate change drivers, and therefore the fate of SOM remains elusive. We sampled soils from a multifactorial climate change experiment in a managed grassland in Austria four years after starting the experiment to investigate the response of SOM in physical soil fractions to temperature (eT: ambient and elevated by +3&#176;C), atmospheric CO2-concentration (eCO2: ambient and elevated by +300 ppm) and to a future climate treatment (eT x eCO2: +3&#176;C and + 300 ppm). A combination of slaking and wet sieving was used to obtain three size classes: macro-aggregates (maA, > 250 &#181;m), micro-aggregates (miA, 63 &#181;m &#8211; 250 &#181;m) and free silt & clay (sc, < 63 &#181;m). In both maA and miA, four different physical OM fractions were then isolated by density fractionation (using sodium polytungstate of &#961; = 1.6 g*cm-3, ultrasonication and sieving): Free POM (fPOM), intra-aggregate POM (iPOM), silt & clay associated OM (SCaOM) and sand-associated OM (SaOM). We measured C and N contents and isotopic composition by EA-IRMS in all fractions and size classes and used a Pyrolysis-GC/MS approach to assess their chemical composition. For eCO2 and eT x eCO2 plots, an isotope mixing-model was used to calculate the proportion of recent C derived from the elevated CO2 treatment. Total soil C and N did not significantly change with treatments.&#160; eCO2 decreased the relative proportion of maA-mineral-associated C and increased C in fPOM and iPOM. About 20% of bulk soil C was represented by the recent C derived from the CO2 fumigation treatment. This significantly differed between size classes and density fractions (p < 0.001), which indicates inherent differences in OM age and turnover. Warming reduced the amount of new C incorporated into size classes. We found that each size class and fraction possessed a unique chemical fingerprint, but this was not significantly changed by the treatments. Overall, our results show that while climate change effects on total soil C were not significant after 4 years, soil fractions showed specific effects. Chemical composition differed significantly between size classes and fractions but was unaffected by simulated climate change. This highlights the importance to separate SOM into differing pools, while including changes to the molecular composition might not be necessary for improving model predictions.&#160;&#160;&#160;&#160;

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Temperature sensitivity of simulated soils with biochars produced at different temperatures

Soil Research ◽

10.1071/sr18226 ◽

2019 ◽

Vol 57 (3) ◽

pp. 294 ◽

Cited By ~ 1

Author(s):

Xiaojie Wang ◽

Guanhong Chen ◽

Renduo Zhang

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Temperature Sensitivity ◽

Pyrolysis Temperature ◽

Soil C ◽

Ambient Temperatures ◽

C Pools ◽

C Cycle ◽

Microbial Enzyme ◽

Different Temperatures

The temperature sensitivity of multiple carbon (C) pools in the soil plays an important role in the C cycle and potential feedback to climate change. The aim of this study was to investigate the temperature sensitivity of different biochars in soil to better understand the temperature sensitivity of different soil C pools. Biochars were prepared using sugarcane residue at temperatures of 300, 500 and 800°C (representing different C pools) and C skeletons (representing the refractory C pool in biochar) were obtained from each biochar. The sugarcane residue, biochars and C skeletons were used as amendments in a simulated soil with microbes but without organic matter. The temperature sensitivity of the amended soils was characterised by their mineralisation rate changes in response to ambient temperatures. The temperature sensitivity of treatments with relatively refractory biochars was higher than that with labile biochars. The temperature sensitivity of treatments with biochars was lower than for their corresponding C skeletons. The different temperature sensitivity of treatments was attributable to the different internal C structures (i.e. the functional groups of C=C and aromatic structure) of amendments, determining the biodegradability of substrates. Dissolved organic matter and microbial enzyme activity of biochars were lower than those of corresponding C skeletons, and decreased with increasing pyrolysis temperature. The temperature sensitivities of treatments with biochars, C skeletons and sugarcane residue were negatively correlated with the properties of dissolved organic matter and microbial enzyme activities (especially dehydrogenase) in soil.

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Unifying soil organic matter formation and persistence frameworks: the MEMS model

Biogeosciences ◽

10.5194/bg-16-1225-2019 ◽

2019 ◽

Vol 16 (6) ◽

pp. 1225-1248 ◽

Cited By ~ 22

Author(s):

Andy D. Robertson ◽

Keith Paustian ◽

Stephen Ogle ◽

Matthew D. Wallenstein ◽

Emanuele Lugato ◽

...

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Model Performance ◽

Soil C ◽

Biogeochemical Models ◽

Novel Approach ◽

C Stocks ◽

Microbial Efficiency ◽

Organic Matter Fractions ◽

Soil Organic Matter Formation

Abstract. Soil organic matter (SOM) dynamics in ecosystem-scale biogeochemical models have traditionally been simulated as immeasurable fluxes between conceptually defined pools. This greatly limits how empirical data can be used to improve model performance and reduce the uncertainty associated with their predictions of carbon (C) cycling. Recent advances in our understanding of the biogeochemical processes that govern SOM formation and persistence demand a new mathematical model with a structure built around key mechanisms and biogeochemically relevant pools. Here, we present one approach that aims to address this need. Our new model (MEMS v1.0) is developed from the Microbial Efficiency-Matrix Stabilization framework, which emphasizes the importance of linking the chemistry of organic matter inputs with efficiency of microbial processing and ultimately with the soil mineral matrix, when studying SOM formation and stabilization. Building on this framework, MEMS v1.0 is also capable of simulating the concept of C saturation and represents decomposition processes and mechanisms of physico-chemical stabilization to define SOM formation into four primary fractions. After describing the model in detail, we optimize four key parameters identified through a variance-based sensitivity analysis. Optimization employed soil fractionation data from 154 sites with diverse environmental conditions, directly equating mineral-associated organic matter and particulate organic matter fractions with corresponding model pools. Finally, model performance was evaluated using total topsoil (0–20 cm) C data from 8192 forest and grassland sites across Europe. Despite the relative simplicity of the model, it was able to accurately capture general trends in soil C stocks across extensive gradients of temperature, precipitation, annual C inputs and soil texture. The novel approach that MEMS v1.0 takes to simulate SOM dynamics has the potential to improve our forecasts of how soils respond to management and environmental perturbation. Ensuring these forecasts are accurate is key to effectively informing policy that can address the sustainability of ecosystem services and help mitigate climate change.

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Regulation of priming effect by soil organic matter stability over a broad geographic scale

Nature Communications ◽

10.1038/s41467-019-13119-z ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 20

Author(s):

Leiyi Chen ◽

Li Liu ◽

Shuqi Qin ◽

Guibiao Yang ◽

Kai Fang ◽

...

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Priming Effect ◽

Basal Respiration ◽

Soil Conditions ◽

The Tibetan Plateau ◽

Geographic Scale ◽

Soil C ◽

Chemical Structures ◽

C Dynamics

Abstract The modification of soil organic matter (SOM) decomposition by plant carbon (C) input (priming effect) represents a critical biogeochemical process that controls soil C dynamics. However, the patterns and drivers of the priming effect remain hidden, especially over broad geographic scales under various climate and soil conditions. By combining systematic field and laboratory analyses based on multiple analytical and statistical approaches, we explore the determinants of priming intensity along a 2200 km grassland transect on the Tibetan Plateau. Our results show that SOM stability characterized by chemical recalcitrance and physico-chemical protection explains more variance in the priming effect than plant, soil and microbial properties. High priming intensity (up to 137% of basal respiration) is associated with complex SOM chemical structures and low mineral-organic associations. The dependence of priming effect on SOM stabilization mechanisms should be considered in Earth System Models to accurately predict soil C dynamics under changing environments.

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Soil organic matter as influenced by straw management practices and inclusion of grass and clover seed crops in cereal rotations

Soil Research ◽

10.1071/sr01103 ◽

2003 ◽

Vol 41 (1) ◽

pp. 95 ◽

Cited By ~ 17

Author(s):

D. Curtin ◽

P. M. Fraser

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Management Practices ◽

Degree Days ◽

Straw Management ◽

Soil C ◽

Total Soil ◽

C And N ◽

Second Year ◽

Seed Crops

In New Zealand, cereal straw has traditionally been burned to facilitate seedbed preparation for the succeeding crop. Because of concerns over the decline of organic matter and the associated deterioration in soil structure, farmers are interested in incorporating crop residues as a means of maintaining organic matter levels. In a 6-year trial on a Wakanui silt loam on the Canterbury Plains, we evaluated the effects of 3 straw management practices (i.e. straw incorporation, burning of straw, and straw removal) on total and labile soil organic matter. A fourth treatment was included to evaluate the local practice of including seed crops (grass and clover) in cereal rotations. The seed crops were grown every second year, the crop sequence being cereal–ryegrass–cereal–clover–cereal–clover. The rate of straw (wheat) decomposition was determined using a litter bag technique, with the bags being buried at a depth of 15 cm for intervals of up to 19 months. In the straw-incorporated treatment, about 25 t/ha of straw (~11 t C/ha) was returned to the soil during the trial. However, there was no significant effect (P > 0.05) of straw management treatments on total soil C (or N), or on labile organic matter pools, although there was a tendency for higher levels of mineralisable C and N where straw was incorporated. Measured straw decomposition rates were consistent with predictions of the Douglas-Rickman residue decomposition model. Under the relatively warm conditions of the Canterbury Plains (thermal time typically >4000 degree-days per year, calculated as the sum of daily degree-days above a base temperature of 0�C), about three-quarters of incorporated straw decomposed within a year. Of the 11 t C/ha of straw-C incorporated, we estimated that only about 1 t C/ha would remain in the soil at the time of sampling. An increase in soil C by this amount would not be detectable (total soil C was about 55 t/ha in the upper 15 cm). Growing seed crops every second year increased several of the labile organic pools (mineralisable C and N, light fraction C and N, microbial biomass) in the 0–7.5 and 7.5 cm soil layers and this may have beneficial effects (e.g. improved N supply) on the succeeding cereal crop. However, the seed crops did not significantly increase total soil organic matter within the 6 years.

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Soil organic matter in rainfed cropping systems of the Australian cereal belt

Soil Research ◽

10.1071/sr99042 ◽

2001 ◽

Vol 39 (3) ◽

pp. 435 ◽

Cited By ~ 139

Author(s):

R. C. Dalal ◽

K. Y. Chan

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Management Practices ◽

Performance Indicator ◽

Annual Rainfall ◽

Soil Productivity ◽

Organic C ◽

Soil C ◽

Eastern Australia

The Australian cereal belt stretches as an arc from north-eastern Australia to south-western Australia (24˚S–40˚S and 125˚E–147˚E), with mean annual temperatures from 14˚C (temperate) to 26˚C (subtropical), and with annual rainfall ranging from 250 mm to 1500 mm. The predominant soil types of the cereal belt include Chromosols, Kandosols, Sodosols, and Vertosols, with significant areas of Ferrosols, Kurosols, Podosols, and Dermosols, covering approximately 20 Mha of arable cropping and 21 Mha of ley pastures. Cultivation and cropping has led to a substantial loss of soil organic matter (SOM) from the Australian cereal belt; the long-term SOM loss often exceeds 60% from the top 0–0.1 m depth after 50 years of cereal cropping. Loss of labile components of SOM such as sand-size or particulate SOM, microbial biomass, and mineralisable nitrogen has been even higher, thus resulting in greater loss in soil productivity than that assessed from the loss of total SOM alone. Since SOM is heterogeneous in nature, the significance and functions of its various components are ambiguous. It is essential that the relationship between levels of total SOM or its identif iable components and the most affected soil properties be established and then quantif ied before the concentrations or amounts of SOM and/or its components can be used as a performance indicator. There is also a need for experimentally verifiable soil organic C pools in modelling the dynamics and management of SOM. Furthermore, the interaction of environmental pollutants added to soil, soil microbial biodiversity, and SOM is poorly understood and therefore requires further study. Biophysically appropriate and cost-effective management practices for cereal cropping lands are required for restoring and maintaining organic matter for sustainable agriculture and restoration of degraded lands. The additional benefit of SOM restoration will be an increase in the long-term greenhouse C sink, which has the potentialto reduce greenhouse emissions by about 50 Mt CO2 equivalents/year over a 20-year period, although current improved agricultural practices can only sequester an estimated 23% of the potential soil C sink.

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Modeling the effects of litter stoichiometry and soil mineral N availability on soil organic matter formation using CENTURY-CUE (v1.0)

Geoscientific Model Development ◽

10.5194/gmd-11-4779-2018 ◽

2018 ◽

Vol 11 (12) ◽

pp. 4779-4796 ◽

Cited By ~ 6

Author(s):

Haicheng Zhang ◽

Daniel S. Goll ◽

Stefano Manzoni ◽

Philippe Ciais ◽

Bertrand Guenet ◽

...

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Litter Quality ◽

Plant Litter ◽

Climate Mitigation ◽

N Availability ◽

Mineral N ◽

Microbial Decomposition ◽

Soil C ◽

C Cycle

Abstract. Microbial decomposition of plant litter is a crucial process for the land carbon (C) cycle, as it directly controls the partitioning of litter C between CO2 released to the atmosphere versus the formation of new soil organic matter (SOM). Land surface models used to study the C cycle rarely considered flexibility in the decomposer C use efficiency (CUEd) defined by the fraction of decomposed litter C that is retained as SOM (as opposed to be respired). In this study, we adapted a conceptual formulation of CUEd based on assumption that litter decomposers optimally adjust their CUEd as a function of litter substrate C to nitrogen (N) stoichiometry to maximize their growth rates. This formulation was incorporated into the widely used CENTURY soil biogeochemical model and evaluated based on data from laboratory litter incubation experiments. Results indicated that the CENTURY model with new CUEd formulation was able to reproduce differences in respiration rate of litter with contrasting C : N ratios and under different levels of mineral N availability, whereas the default model with fixed CUEd could not. Using the model with flexible CUEd, we also illustrated that litter quality affected the long-term SOM formation. Litter with a small C : N ratio tended to form a larger SOM pool than litter with larger C : N ratios, as it could be more efficiently incorporated into SOM by microorganisms. This study provided a simple but effective formulation to quantify the effect of varying litter quality (N content) on SOM formation across temporal scales. Optimality theory appears to be suitable to predict complex processes of litter decomposition into soil C and to quantify how plant residues and manure can be harnessed to improve soil C sequestration for climate mitigation.

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CO2 fluxes and carbon balance of an agricultural grassland in southern Finland

10.5194/egusphere-egu2020-6618 ◽

2020 ◽

Author(s):

Laura Heimsch ◽

Annalea Lohila ◽

Liisa Kulmala ◽

Juha-Pekka Tuovinen ◽

Mika Korkiakoski ◽

...

Keyword(s):

Climate Change ◽

Organic Matter ◽

Soil Organic Matter ◽

Carbon Balance ◽

Management Practices ◽

Agricultural Soils ◽

Weather Conditions ◽

Factors Affecting ◽

Management Procedures ◽

Mitigate Climate Change

Agriculture is globally a significant source of carbon emissions to the atmosphere. Main causes for these high emissions are conventional intensive management practices which include such as frequent ploughing, monocropping and high use of agrochemicals. These practices contribute to the loss of biodiversity and soil organic matter, as well as to the CO2 emissions from land use. Recently, it has been recognised that agriculture functioning on the basis of regenerative practices is one of the most potential tools to mitigate climate change.It is well known that topsoil layer and especially humus-rich soils can store more carbon than atmosphere and vegetation together. Therefore, increasing the amount of soil organic matter in the agroecosystems, by applying enhanced management practices such as reduced tillage, high biodiversity and cover cropping, agricultural soils would not only help to mitigate climate change but also to restore soil quality and fertility. To understand the carbon dynamics on different agricultural sites, factors affecting and comprising the carbon balance, and to verify soil carbon and ecosystem models, continuous long-term monitoring of the GHG fluxes is essential at such managed ecosystems. Here we present results from a new eddy covariance (EC) flux study site located in southern Finland.Continuous CO2 flux measurements using the EC method have been conducted at Qvidja farm on mineral (clay) soil forage grassland in Parainen, southern Finland (60.29550&#176;N, 22.39281&#176;E) since the spring 2018. Based on the flux and biomass data, the annual carbon balance was estimated to be negative, i.e. the site acted as an overall sink of carbon even in the dry and hot year 2018. However, the seasonal CO2 fluxes were greatly dependent on weather conditions and management procedures. Results from 2019 show that the growing season accompanied with more mature and dense grass, a bit higher precipitation and lower temperatures, as well as higher cutting height was more favorable for carbon uptake in Qvidja as compared to year 2018.

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