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

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.

Download Full-text

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

10.5194/bg-2018-430 ◽

2018 ◽

Cited By ~ 2

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 upon 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.

Download Full-text

Spatial patterns in soil organic matter dynamics are shaped by mycorrhizosphere interactions in a treeline forest

Plant and Soil ◽

10.1007/s11104-019-04398-y ◽

2019 ◽

Vol 447 (1-2) ◽

pp. 521-535

Author(s):

Nina L. Friggens ◽

Thomas J. Aspray ◽

Thomas C. Parker ◽

Jens-Arne Subke ◽

Philip A. Wookey

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Spatial Scales ◽

Mountain Birch ◽

Organic C ◽

Soil C ◽

Soil Organic Matter Dynamics ◽

C Stocks ◽

Organic Matter Dynamics ◽

Individual Trees

Abstract Aims In the Swedish sub-Arctic, mountain birch (Betula pubescens ssp. czerepanovii) forests mediate rapid soil C cycling relative to adjacent tundra heaths, but little is known about the role of individual trees within forests. Here we investigate the spatial extent over which trees influence soil processes. Methods We measured respiration, soil C stocks, root and mycorrhizal productivity and fungi:bacteria ratios at fine spatial scales along 3 m transects extending radially from mountain birch trees in a sub-Arctic ecotone forest. Root and mycorrhizal productivity was quantified using in-growth techniques and fungi:bacteria ratios were determined by qPCR. Results Neither respiration, nor root and mycorrhizal production, varied along transects. Fungi:bacteria ratios, soil organic C stocks and standing litter declined with increasing distance from trees. Conclusions As 3 m is half the average size of forest gaps, these findings suggest that forest soil environments are efficiently explored by roots and associated mycorrhizal networks of B. pubescens. Individual trees exert influence substantially away from their base, creating more uniform distributions of root, mycorrhizal and bacterial activity than expected. However, overall rates of soil C accumulation do vary with distance from trees, with potential implications for spatio-temporal soil organic matter dynamics and net ecosystem C sequestration.

Download Full-text

ORGANIC MATTER FRACTIONS IN A QUARTZIPSAMMENT UNDER CULTIVATION OF IRRIGATED MANGO IN THE LOWER SÃO FRANCISCO VALLEY REGION, BRAZIL

Revista Brasileira de Ciência do Solo ◽

10.1590/01000683rbcs20140498 ◽

2015 ◽

Vol 39 (4) ◽

pp. 1068-1078 ◽

Cited By ~ 4

Author(s):

José Alberto Ferreira Cardoso ◽

Augusto Miguel Nascimento Lima ◽

Tony Jarbas Ferreira Cunha ◽

Marcos Sales Rodrigues ◽

Luis Carlos Hernani ◽

...

Keyword(s):

Organic Matter ◽

Humic Acid ◽

Soil Organic Matter ◽

Fulvic Acid ◽

Agricultural Production ◽

Soil Layer ◽

Soil Samples ◽

C Stocks ◽

Organic Matter Fractions ◽

The Impact

Improper land use has lead to deterioration and depletion of natural resources, as well as a significant decline in agricultural production, due to decreased soil quality. Removal of native vegetation to make way for agricultural crops, often managed inadequately, results in soil disruption, decreased nutrient availability, and decomposition of soil organic matter, making sustainable agricultural production unviable. Thus, the aim of the present study was to evaluate the impact of growing irrigated mango (over a 20 year period) on the organic carbon (OC) stocks and on the fractions of soil organic matter (SOM) in relation to the native caatinga (xeric shrubland) vegetation in the Lower São Francisco Valley region, Brazil. The study was carried out on the Boa Esperança Farm located in Petrolina, Pernambuco, Brazil. In areas under irrigated mango and native caatinga, soil samples were collected at the 0-10 and 10-20 cm depths. After preparing the soil samples, we determined the OC stocks, carbon of humic substances (fulvic acid fractions, humic acid fractions, and humin fractions), and the light and heavy SOM fractions. Growing irrigated mango resulted in higher OC stocks; higher C stocks in the fulvic acid, humic acid, and humin fractions; and higher C stocks in the heavy and light SOM fraction in comparison to nativecaatinga, especially in the uppermost soil layer.

Download Full-text

Soil texture mediated microbial activity affects the transfer of litter-derived carbon to soil organic matter

10.5194/egusphere-egu2020-10898 ◽

2020 ◽

Author(s):

Gerrit Angst ◽

Jan Pokorný ◽

Travis Meador ◽

Tomáš Hajek ◽

Jan Frouz ◽

...

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Microbial Activity ◽

Litter Decomposition ◽

Soil Texture ◽

Mineral Soil ◽

C Sequestration ◽

Soil Microbial Activity ◽

Soil C ◽

Soil Organic Matter Formation

Knowledge about the nexus between litter decomposition and soil organic matter formation is still scarce, likely because litter decomposition studies are often conducted in the absence of mineral soil. Even if mineral soil is considered, variations in soil texture, which should substantially influence decomposition and soil C sequestration via, e.g., different capacities to store C or host microbial communities, have been neglected. Here, we examined the effect of soil texture on litter decomposition and soil organic matter formation by incubating sand- and clay-rich soils. These soils, taken under C3 vegetation, were amended with C4 litter to trace the fate of organic matter newly entering the soil. While we found only small amounts of litter-derived carbon (C) in the mineral soils after our six-month experiment, the microbial activity and amount of remaining litter between the sand- and clay-rich soils substantially differed. A high microbial activity combined with higher amounts of litter-derived C and a higher remaining litter mass in the clay-rich soil indicate a more effective transformation of litter to soil organic matter as compared to the sand-rich soil. In the sand-rich soil, microbial activity was lower, less soil C was litter-derived, and the litter lost more of its mass. We explain the apparently contradictory results of higher microbial activity and concurrently higher C contents with a more effective microbial pathway of SOM formation in the clay-rich soil. Our results indicate that soil texture does not only play a role in the provision of reactive surfaces for the stabilization of C but will also affect the decomposition of litter via effects on microbial activity, ultimately determining if litter C is transferred to the soil or respired to the atmosphere.

Download Full-text

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.

Download Full-text

Reviews and syntheses: The mechanisms underlying carbon storage in soil

10.5194/bg-2020-49 ◽

2020 ◽

Cited By ~ 2

Author(s):

Isabelle Basile-Doelsch ◽

Jérôme Balesdent ◽

Sylvain Pellerin

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Abiotic Factors ◽

Soil C ◽

Carbon Production ◽

C Stocks ◽

Organomineral Interactions ◽

Living Organisms ◽

Major Factors

Abstract. Scientific research in the 21st century has considerably improved our knowledge of soil organic matter and its dynamics, particularly under the pressure of the global disruption of the carbon cycle. This paper reviews the processes that control C dynamics in soil, the representation of these processes over time, and their dependence on variations in major biotic and abiotic factors. The most recent advances in soil organic matter knowledge are: – Most organic matter is composed of small molecules, derived from living organisms, without transformation via additional abiotic organic polymerization. – Microbial compounds are predominant in the long term. – Primary belowground production contributes more to organic matter than aboveground inputs. – Contribution of less biodegradable compounds to soil organic matter is low in the long term. – Two major factors determine the soil organic carbon production yield from the initial substrates: the yield of carbon used by microorganisms and the association with minerals, particularly poorly crystallized minerals, which stabilize microbial compounds. – Interactions between plants and microorganisms and between microbial communities affect or even regulate carbon residence times, and therefore carbon stocks. Farming practices therefore affect soil C stocks not only through carbon inputs but also via their effect on microbial and organomineral interactions.

Download Full-text

Cover plants and mineral nitrogen: effects on organic matter fractions in an oxisol under no-tillage in the cerrado

Revista Brasileira de Ciência do Solo ◽

10.1590/s0100-06832014000600022 ◽

2014 ◽

Vol 38 (6) ◽

pp. 1874-1881 ◽

Cited By ~ 5

Author(s):

Isis Lima dos Santos ◽

Carla Ferreira Caixeta ◽

Alex Antônio Torres Cortês de Sousa ◽

Cícero Célio de Figueiredo ◽

Maria Lucrécia Gerosa Ramos ◽

...

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Cover Crops ◽

Block Design ◽

N Fertilization ◽

No Tillage ◽

Organic C ◽

Soil C ◽

Tropical Regions ◽

Organic Matter Fractions

Cover plants are essential for the sustainability of no-tillage systems in tropical regions. However, information on the effects of these plants and N fertilization on soil organic matter fractions is still scarce. This study evaluated the effect of cover crops with different chemical composition and of N topdressing on the labile and humified organic matter fractions of an Oxisol of the Cerrado (savanna-like vegetation). The study in a randomized complete block design was arranged in split-plots with three replications. Four cover species were tested in the plots and the presence or absence of N topdressing in the subplot. The following cover species were planted in succession to corn for eight years: Urochloa ruziziensis; Canavalia brasiliensis M. ex Benth; Cajanus cajan (L.) Millsp; and Sorghum bicolor (L.) Moench. In general, the cultivation of U. ruziziensis increased soil C levels, particularly of C in the humic acid and particulate organic C fractions, which are quality indicators of soil organic matter. The C in humic substances and mineral organic C accounted for the highest proportions of total organic C, demonstrating the strong interaction between organic matter, Fe and Al oxides and kaolinite, which are predominant in these weathered soils of the Cerrado.

Download Full-text

C stocks and subsoil management in agroecosystems: application of hyperspectral imaging to study organic matter dynamics in the top one metre of soil

10.5194/egusphere-egu2020-20653 ◽

2020 ◽

Author(s):

Julien Guigue ◽

Christopher Just ◽

Siwei Luo ◽

Eleanor Hobley ◽

Ingrid Kögel-Knabner

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Hyperspectral Imaging ◽

Environmental Changes ◽

Crop Productivity ◽

Soil Cores ◽

Deep Soil ◽

Demographic Pressure ◽

Soil C ◽

C Stocks

While the demographic pressure for food demand is continuously rising, global environmental changes are threatening the productivity of agroecosystems. Climatic events like floods or droughts, and long-term decrease in soil organic matter stocks due to intensive agriculture are examples pointing to the necessity to find solutions for sustainable performance of agroecosystems.Significant amounts of water and nutrients are stored in deep soil horizons, and thus subsoil management is being considered as an alternative to sustain high demand in crop productivity. We used samples from an ongoing field experiment in Germany where the agricultural management was adapted to investigate the potential benefits of deep ploughing with OM incorporation. We recorded hyperspectral images of soil cores (depth = 1 m) using Vis-NIR reflectance spectroscopy and the C distribution within the soil was modeled at a very high spatial resolution (53&#215;53 &#956;m). The SOC mapping revealed an increase in SOC stocks resulting from deep ploughing, and the high resolution images generated allows the observation of OM distribution in the subsoil and the response in SOM stocks to different types of organic matter incorporation (compost vs green manure). The same imaging technique was also combined with solid-state 13C NMR measurements to track the molecular composition of the organic amendment during decomposition.Hyperspectral imaging of soil cores allows the quantification of OM stocks and changes at the pedon scale, and fine scale resolution of heterogeneity in the spatial distribution of soil organic matter is helping to understand and quantify the processes related to changes in soil C stocks in subsoils.

Download Full-text

Soil organic matter in fire-affected pastures and in an Araucaria forest in South-Brazilian Leptosols

Pesquisa Agropecuária Brasileira ◽

10.1590/s0100-204x2012000500011 ◽

2012 ◽

Vol 47 (5) ◽

pp. 707-715 ◽

Cited By ~ 11

Author(s):

Mariana da Luz Potes ◽

Deborah Pinheiro Dick ◽

Graciele Sarante Santana ◽

Michely Tomazi ◽

Cimélio Bayer

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Grazing Intensity ◽

Soil C ◽

Araucaria Forest ◽

Physical Fractionation ◽

C Stocks ◽

Native Pasture ◽

Soil C And N ◽

C And N

The objective of this work was to evaluate the distribution pattern and composition of soil organic matter (SOM) and its physical pools of Leptosols periodically affected by fire over the last 100 years in South Brazil. Soil samples at 0-5, 5-10, and 10-15 cm depths were collected from the following environments: native pasture without burning in the last year and grazed with 0.5 livestock per hectare per year (1NB); native pasture without burning in the last 23 years and grazed with 2.0 livestock per hectare per year (23NB); and an Araucaria forest (AF). Physical fractionation was performed with the 0-5 and 5-10 cm soil layers. Soil C and N stocks were determined in the three depths and in the physical pools, and organic matter was characterized by infrared spectroscopy and thermogravimetry. The largest C stocks in all depths and physical pools were found under the AF. The 23NB environment showed the lowest soil C and N stocks at the 5-15 cm depth, which was related to the end of burning and to the higher grazing intensity. The SOM of the occluded light fraction showed a greater chemical recalcitrance in 1NB than in 23NB. Annual pasture burning does not affect soil C stocks up to 15 cm of depth.

Download Full-text

Reviews and syntheses: The mechanisms underlying carbon storage in soil

Biogeosciences ◽

10.5194/bg-17-5223-2020 ◽

2020 ◽

Vol 17 (21) ◽

pp. 5223-5242 ◽

Cited By ~ 1

Author(s):

Isabelle Basile-Doelsch ◽

Jérôme Balesdent ◽

Sylvain Pellerin

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Abiotic Factors ◽

Agricultural Practices ◽

Turnover Time ◽

Carbon Turnover ◽

Soil C ◽

C Dynamics ◽

C Stocks

Abstract. Soil organic matter (OM) represents a key C pool for climate regulation but also an essential component for soil functions and services. Scientific research in the 21st century has considerably improved our knowledge of soil organic matter and its dynamics, particularly under the pressure of the global disruption of the carbon cycle. This paper reviews the processes that control C dynamics in soil, the representation of these processes over time, and their dependence on variations in major biotic and abiotic factors. The most recent advanced knowledge gained on soil organic matter includes the following. (1) Most organic matter is composed of small molecules, derived from living organisms, without transformation via additional abiotic organic polymerization; (2) microbial compounds are predominant in the long term; (3) primary belowground production contributes more to organic matter than aboveground inputs; (4) the contribution of less biodegradable compounds to soil organic matter is low in the long term; (5) two major factors determine the soil organic carbon production “yield” from the initial substrates: the yield of carbon used by microorganisms and the association with minerals, particularly poorly crystalline minerals, which stabilize microbial compounds; (6) interactions between plants and microorganisms also regulate the carbon turnover time and therefore carbon stocks; (7) among abiotic and biotic factors that regulate the carbon turnover time, only a few are considered in current modeling approaches (i.e., temperature, soil water content, pH, particle size, and sometimes C and N interactions); and (8) although most models of soil C dynamics assume that the processes involved are linear, there are now many indications of nonlinear soil C dynamics processes linked to soil OM dynamics (e.g., priming). Farming practices, therefore, affect soil C stocks not only through carbon inputs but also via their effect on microbial and organomineral interactions, yet it has still not been possible to properly identify the main mechanisms involved in C loss (or gain). Greater insight into these mechanisms and their interdependencies, hierarchy and sensitivity to agricultural practices could provide future levers of action for C sequestration in soil.

Download Full-text