Changes In Soil Carbon Stocks Research Articles

Soil carbon stock changes in a crop-livestock-forestry integration in Southern Goiás State, Brazil

Soil carbon stock changes in a crop-livestock-forestry integration in Southern Goiás State, Brazil

A global analysis of the effects of forest thinning on soil N stocks and dynamics

Forest thinning is a critical management measure for changing the forest community structure and improving the soil microclimate and nitrogen (N) cycle. However, differences in forest types, thinning intensity, recovery time, and climate conditions make the accumulation of soil N under forest thinning uncertain; especially the soil N accumulation rate is still lacking. This study systematically discusses the effects of forest thinning on the rate of soil N stock change (RNC) and analyzes the relationship between the RNC and the rate of soil carbon (C) stock change (RCC) by synthesizing 387 global data points. Forest thinning significantly increased the soil N stock, with the RNC being +0.07 Mg/ha yr−1. The RNCs in coniferous and mixed forests (+0.07 and +0.09 Mg/ha yr−1, respectively) were higher than that in broadleaf forest (−0.03 Mg/ha yr−1). Heavy forest thinning inhibited soil N accumulation; however, light forest thinning and long-term recovery were more conducive to improving it. The RNC decreased with increasing precipitation and temperature under forest thinning. Additionally, the RNC was positively correlated with the RCC. Overall, heavy forest thinning decreases the soil N accumulation rate in the global forest ecosystem; conversely, long-term recovery increases it. Reducing the forest thinning intensity and extending the recovery time can accelerate soil N accumulation and thus reduce greenhouse gas emissions.

Insights into effects of conventional and biodegradable microplastics on organic carbon decomposition in different soil aggregates

The impacts of microplastics on soil ecological functions such as carbon recycling and soil structure maintenance have been extensively focused. However, the mechanisms underlying the impacts of microplastics on soil carbon transformation and soil microbial community at soil aggregate scale have not been clarified yet. In this work, the effects and action mechanisms of traditional microplastic polypropylene (PP) and degradable microplastic polylactic acid (PLA) on carbon transformation in three sizes of soil aggregates were investigated. The results showed that both PP and PLA promoted CO2 emission, and the effect depended on the type and content of microplastics, and the size of soil aggregates. Changes in soil carbon stocks were mainly driven by changes in organic carbon associated with macroaggregates. For macroaggregates, PP microplastics decreased soil organic carbon (SOC) as well as dissolved organic carbon (DOC). These changes were reversed in microaggregates and silt and clay. Interestingly, PLA increased the SOC, DOC and CO2 emissions in bulk soil and all three aggregates with a dose-effect response. These changes were associated with soil microbes, functional genes and enzymes associated with the degradation of labile and recalcitrant carbon fractions. Furthermore, PP and PLA reduced bacterial community diversities and shifted bacterial community structures in both the three aggregates and in bulk soil. Alterations of functional genes induced by microplastics were the key driving factors of their impacts on carbon transformation in soil aggregates. This research opened up a new insight into the mechanisms underlying the impacts of microplastics on soil carbon transformation, and helped us make rational assessments of the risks and the disturbances of microplastics on soil carbon cycling.

Methodology for evaluating soil carbon stock changes based on regional geochemical survey data: A case study in Huangpi, China

Soil carbon pools play a crucial role in the Earth's ecosystem, acting as significant carbon sinks and sources. Through a detailed analysis of soil carbon content using data from the Huangpi District in Wuhan, China, this research employs geochemical survey data, field replicates, and spatial autocorrelation information to establish an assessment model for soil carbon stocks. The model addresses the sources of errors and their effects on carbon pool changes, using both traditional statistical theories and geostatistical models to detect changes in carbon density and estimate carbon sources and sinks with minimized error ranges. Key findings indicate that sampling errors, influenced by small-scale spatial variability, are the primary source of observational inaccuracies in assessing total soil carbon and organic carbon, accounting for over 90% of the variation. Meanwhile, analytical errors are more significant when quantifying soil inorganic carbon content due to its lower concentrations. From 2001 to 2022, no significant changes were observed in the soil organic carbon stock in Huangpi District, while a modest increase in inorganic carbon was noted. The study highlights that increasing sample density beyond a certain threshold does not significantly affect carbon stock estimates or their error ranges, emphasizing the stability of the block kriging method in estimating regional carbon stocks.

Greenhouse gas emissions and nutrient use efficiency assessment of six New York organic dairies

Improving nutrient use efficiency and reducing greenhouse gas (GHG) emissions are important environmental priorities for organic-certified dairy operations. The objectives of this research were to quantify annual nutrient use and GHG emissions in 6 organic New York dairy farms. Farm-gate nutrient mass balances (NMB) were estimated with the Cornell NMB calculator. Whole-farm GHG emissions were estimated using Cool Farm Tool (CFT) and COMET. Farm-gate NMBs were low, ranging from -6.5 to 19 kg N ha-1 for N1 (without legume N fixation), 26 to 71 kg N ha-1 for N2 (including N fixation), -2.4 to 8.2 kg P ha-1 for P, and 1.1 to 19.8 kg K ha-1 for K. Additional nutrient imports, coupled with nutrient management planning, adequate legume stands and diet balancing may help improve P balances, and ensure no N deficiencies in the system. Estimates of annual GHG emission intensity ranged from 0.98 to 2.10 kg CO2-eq per kg of fat and protein corrected milk (FPCM) estimated by CFT, and from 0.69 to 2.48 kg CO2-eq kg FPCM-1 estimated by COMET. Enteric fermentation, feed production and fuel and energy use represented the largest sources of GHGs. For farms with liquid manure storages, manure management was also a significant source. Estimates of soil carbon (C) stock changes from CFT were in agreement or smaller than previous studies, and estimates from COMET were in agreement or greater. Variability and uncertainty in the results for soil C stock change indicate more research and new protocols are needed. Impact of individual management changes on GHG emissions intensity were small, ranging from -8 to +7% in CFT, and -8% to +8% in COMET. The management changes that resulted in the largest reductions in GHG emissions intensity included increasing individual cow productivity and milk to total feed ratio, and implementation of manure treatment systems.

Spatial changes in soil carbon stock through patches and inter-patch open spaces in pure shrub-lands of central Iran

Spatial changes in soil carbon stock through patches and inter-patch open spaces in pure shrub-lands of central Iran

Is the organic carbon-to-clay ratio a reliable indicator of soil health?

Climate action plans under the Paris Climate Agreement and other national commitments aimed at improving soil-based ecosystem services require the operational monitoring of soil carbon (C). The European Union is aiming to enhance soil health, and as part of the proposed Soil Monitoring Law, the European Commission recommends the monitoring of the soil C loss indicator among other soil health indicators. In this study, we evaluate the feasibility of the proposed soil C loss indicator by assessing its performance using the EU-wide 2009 LUCAS soil survey data. The proposed indicator is the soil organic carbon (SOC) to clay ratio, with a threshold value of 1:13. The results are also compared with the C stock changes reported by countries to the climate convention (UNFCCC). Our results reveal that the variation in SOC and clay content at European scale exceeds that of the data used to develop the proposed indicator. We also found that the variation in the SOC content was influenced not only by clay content but also by climate and land-use reflecting C input levels. Therefore, the defined threshold is inadequate for detecting degraded soils if the SOC and clay content are beyond the conditions used to establish the criteria. Furthermore, major discrepancies were observed between the soil carbon stock changes reported by the national greenhouse gas (GHG) inventories and the proportions of degraded soils identified by using the soil C loss indicator. We conclude that employing a single indicator such as SOC:Clay ratio with one threshold value for all soils across various land covers, management practices, and climatic conditions, as defined by the European Commission for the Soil Monitoring Law, is inappropriate for monitoring soil C loss.

Evaluation and optimisation of the soil carbon turnover routine in the MONICA model (version 3.3.1)

Abstract. Simulation models are tools commonly used to predict changes in soil carbon stocks. Prior validation is essential, however, for determining the reliability and applicability of model results. In this study, the process-based biogeochemical model MONICA (Model of Nitrogen and Carbon dynamics on Agro-ecosystems) was evaluated with respect to soil organic carbon (SOC), using long-term monitoring data from 46 German agricultural sites. A revision and parameterisation of equations, encompassing crop- and fertiliser-specific C contents and the abiotic factors of soil temperature, soil water and clay content, were undertaken and included in the model. The modified version was also used for a Morris elementary effects screening method, which confirmed the importance of environmental and management factors to the model's performance. The model was then calibrated by means of Bayesian inference, using the Metropolis–Hastings algorithm. The performance of the MONICA model was compared with that of five established carbon turnover models (CCB, CENTURY, C-TOOL, ICBM and RothC). The original MONICA model systematically overestimated SOC decomposition rates and produced on average a ∼17 % greater mean absolute error (MAE) than the other models. The modification and calibration significantly improved its performance, reducing the MAE by ∼30 %. Consequently, MONICA outperformed CENTURY, CCB and C-TOOL, and produced results comparable with ICBM and RothC. Use of the modified model allowed mostly adequate reproduction of site-specific SOC stocks, while the availability of a nitrogen, plant growth and water submodel enhanced its applicability when compared with models that only describe carbon dynamics.

A fuzzy logic evaluation of synergies and trade-offs between agricultural production and climate change mitigation

This study introduces a trade-off evaluation system, the Σommit index, which considers four components: crop yield, soil carbon stock changes, direct and indirect nitrous oxide emissions, and nitrate-nitrogen leaching across alternative agronomic case scenarios, i.e., combinations of management practices within specific pedo-climatic conditions. The four trade-off components have been estimated by combining standard equations and emission factors from the Guidelines for National Greenhouse Gas Inventories, complemented with Grey Water Footprint accounting Guidelines and other meta-analyses. The Σommit index has been developed using a harmonised dataset of ∼1.8 million agronomic case scenarios, leveraging fuzzy logic to aggregate the trade-off components into a value ranging from 0 (bad) to 1 (good). It has been tested under three narratives reflecting stakeholders' sustainability priorities (young farmers, agrochemical companies, EU Common Agricultural Policy paying agency), using alternative weighting schemes derived from expert opinion. Adding organic matter input, intermediate N fertilisation (50–150 kg ha−1), no-tillage, winter cereal cultivation, and irrigation for summer cereals have consistently achieved higher performance across all narratives. When assigning a higher weight to soil carbon stock changes, a broader range of Σommit index values emerged, while assigning higher importance to crop yield has led to a narrower evaluation. We openly release the dataset of agronomic case scenarios, along with the scripts to replicate the methodology and an interactive dashboard to inspect the results. These resources are meant to be used by different stakeholders (e.g., policymakers, Common Agricultural Policy payment agencies, farms, agrochemical industry) as a complement to the Intergovernmental Panel on Climate Change methodology to improve current understanding and awareness of environmental trade-offs and synergies in agricultural management.

The importance of accounting method and sampling depth to estimate changes in soil carbon stocks

BackgroundAs interest in the voluntary soil carbon market surges, carbon registries have been developing new soil carbon measurement, reporting, and verification (MRV) protocols. These protocols are inconsistent in their approaches to measuring soil organic carbon (SOC). Two areas of concern include the type of SOC stock accounting method (fixed-depth (FD) vs. equivalent soil mass (ESM)) and sampling depth requirement. Despite evidence that fixed-depth measurements can result in error because of changes in soil bulk density and that sampling to 30 cm neglects a significant portion of the soil profile’s SOC stock, most MRV protocols do not specify which sampling method to use and only require sampling to 30 cm. Using data from UC Davis’s Century Experiment (“Century”) and UW Madison’s Wisconsin Integrated Cropping Systems Trial (WICST), we quantify differences in SOC stock changes estimated by FD and ESM over 20 years, investigate how sampling at-depth (> 30 cm) affects SOC stock change estimates, and estimate how crediting outcomes taking an empirical sampling-only crediting approach differ when stocks are calculated using ESM or FD at different depths.ResultsWe find that FD and ESM estimates of stock change can differ by over 100 percent and that, as expected, much of this difference is associated with changes in bulk density in surface soils (e.g., r = 0.90 for Century maize treatments). This led to substantial differences in crediting outcomes between ESM and FD-based stocks, although many treatments did not receive credits due to declines in SOC stocks over time. While increased variability of soils at depth makes it challenging to accurately quantify stocks across the profile, sampling to 60 cm can capture changes in bulk density, potential SOC redistribution, and a larger proportion of the overall SOC stock.ConclusionsESM accounting and sampling to 60 cm (using multiple depth increments) should be considered best practice when quantifying change in SOC stocks in annual, row crop agroecosystems. For carbon markets, the cost of achieving an accurate estimate of SOC stocks that reflect management impacts on soils at-depth should be reflected in the price of carbon credits.

Carbon stock changes of drained nutrient-rich organic forest soils in Latvia

Impact of drainage of organic soils in forest land on soil carbon (C) stock changes is of high interest not only to accurately estimate soil C stock changes, but also to provide scientifically based recommendations for forest land management in context of climate change mitigation. To improve knowledge about long-term impact of drainage on nutrient-rich organic soils in hemiboreal forests in Latvia, 50 research sites representing drained conditions (Oxalidosa turf. mel. (Kp) and Myrtillosa turf. mel. (Ks) forest site types) and undrained conditions as control areas (Caricoso-phragmitosa, Dryopterioso-caricosa and Filipendulosa forest site types) were selected. Soil C stock changes after drainage was evaluated by comparing current C stock in drained organic soils to theoretical C stock before drainage considering impact of soil subsidence. During the 53-years period after drainage, the peat subsidence was higher in nutrient-rich Kp forest site type compared to moderate nutrient-rich Ks forest site type (peat subsided by 37.0 ± 4.8 and 23.3 ± 4.8 cm, respectively). In nutrient-rich Kp forest site type, soil C stock decreased by 4.98 ± 1.58 Mg C ha–1 yr–1 after drainage, while no statistically significant changes in soil C stock (0.19 ± 1.31 Mg C ha–1 yr–1) were observed in moderate nutrient-rich soils in Ks forest site type. Thus, in Ks forest site type, the main driver of the peat subsidence was the physical compaction, while in Kp forest site type contribution of organic matter decomposition and consequent soil C losses to subsidence of the peat was significant.

Net global warming potential index rather than soil carbon stock change could provide better understanding of the carbon balance in soil systems.

This study was conducted to determine the soil organic carbon (SOC) stock change factor for green manure crops that was developed by the Intergovernmental Panel on Climate Change (IPCC) Tier 2 method and compare this with the net global warming potential (GWP) index that is used to evaluate the contribution of green manuring to global warming. Four treatments were barley (Hordeum vulgare L.; B), hairy vetch (Vicia villosa R.; HV), a barley/hairy vetch mixture (BHV) and a conventional treatment (C). The aboveground biomass of green manure crops was incorporated into the soil on 25 May 2018, 26 April 2019, 29 April 2020, 30 April 2021 and 2 May 2022. Maize (Zea mays L.) was transplanted as the subsequent crop after the incorporation of green manures. SOC stock decreased with green manures, even though carbon input with green manures, including B, HV and BHV, was greater than that with C. The mean value of the SOC stock change factor for green manure crops, including B, HV and BHV was 0.627 and was significantly lower than that of the C. However, the net GWP also decreased with the incorporation of green manure crops, and the mean value of the relative net GWP index across B, HV and BHV was 0.853. These conflicting results were caused by different estimation methods between annual SOC change (△SOC) and net GWP. The estimation of SOC stock change using △SOC suggested by the IPCC method may overestimate the contribution of green manure crops to global warming. The net GWP method with comprehensive input and output of carbon in the soil system could provide a better understanding of the carbon balance in soil systems. In the current study, the comparison of △SOC and net GWP was conducted for at one site of upland soil for 5years. Therefore, further research on estimating the effect of green manure crops on net GWP in various types of soil for longer years should be conducted.

Агроэкологическая характеристика черноземов Каменной степи: влияние растительных сообществ и распашки

Changes in soil carbon stocks have a significant impact on atmospheric CO2 concentrations and the global carbon balance. Despite the proven effectiveness of agroforestry in erosion control and prevention of soil fertility loss, there are many controversial data suggesting that the impact of afforestation on Chernozem soils should be further investigated. The Kamennaya Steppe site (arable land surrounded by shelterbelt forests) is a reference site for monitoring studies at the Voronezh Carbon Test Site, where the carbon balance of agro-ecosystems is being studied and the ecological role of shelterbelt forests in changing soil properties and carbon sequestration is being evaluated. The study was focused on the evaluation of agro-ecological characteristics and the impact of tillage on Chernozems of Kamennaya Steppe under different vegetation types. The study of the chemical properties of chernozems was carried out using classical chemical methods; the analysis of heavy metals was carried out using the voltampermetric method. Comprehensive agro-ecological evaluation showed that the studied Vorony-Calcic Chernozems had a high content of humus, which reached 7-8% in the upper horizons, enriched with mineral nutrition elements, and had favorable physical and chemical properties. Forest and grassland vegetation contribute to enrichment of the soil with organic residues, while tillage and mineralization of organic matter on arable land led to a decrease in humus content. Data analysis suggested that the study area did not suffer from contamination. Furthermore, it was found that the organic matter of the studied chernozems was able to bind the studied metals and retain them in an unavailable state. This phenomenon was supported by rather high correlations between humus and total heavy metal content (r = 0.946 for Pb and r = 0.975 for Cd at p < 0.00001). It should be emphasized that shelterbelt forests could act as a biogeochemical barrier to the lateral migration of heavy metals. Cadmium is a rather mobile element potentially capable to migrate to adjacent environments. Therefore, regular monitoring of the agro-ecological condition of the Chernozems of the Kamennaya Steppe is required.

Increase in Soil Carbon Pool Stability Rather Than Its Stock in Coastal Saline—Alkali Ditches following Reclamation Time

Extensive drainage ditches are constructed to reduce soil salinity in reclaimed saline–alkali farmland, consequently forming plant growth hotspots and impacting soil carbon stocks therein. However, the investigation into changes in soil carbon stocks remains limited in these ditches. To address this, soil samples were collected from drainage ditches, which originated from the reclamation of saline–alkali farmland, at different reclamation years (the first, seventh, and fifteenth year). Moreover, fractions were separated from soil samples; a particle size separation method (particulate organic matter, POM; mineral–associated organic matter, MAOM) and a spatio–temporal substitution method were conducted to analyze the variations in soil carbon components and the underlying mechanisms. The results indicate that there were no significant variations in the contents and stocks of soil organic carbon (SOC) and soil inorganic carbon (SIC) following the increase in reclamation time. However, in the POM fraction, the SOC content (SOCPOM) and stock significantly decreased from 2.24 to 1.12 g kg−1 and from 19.02 to 12.71 Mg ha−1, respectively. Conversely, in the MAOM fraction, the SOC content (SOCMAOM) and stock significantly increased from 0.65 to 1.70 g kg−1 and from 5.30 to 12.27 Mg ha−1, respectively. The different changes in SOCPOM and SOCMAOM, as well as the result of the structural equation model, showed a possible transformation process from SOCPOM to SOCMAOM in the soil carbon pool under the driving force of reclamation time. The results in terms of the changes in soil carbon components demonstrate the stability rather than the stock of the soil carbon pool increase in coastal saline–alkali ditches following the excavation formation time. Although more long time series and direct evidence are needed, our findings further provide a case study for new knowledge about changes in the soil carbon pool within saline–alkali ditches and reveal the potential processes involved in the transformation of soil carbon components.

The emerging global agricultural soil carbon market: the case for reconciling farmers’ expectations with the demands of the market

In the absence of a global environmental policy framework to standardise the monitoring, reporting and verification of soil carbon stock changes and/or reductions in soil-derived greenhouse gas emissions, private sector and civil society organisations have played a key role in governing the production and trade, and/or direct sale of carbon credits. This paper takes the United Kingdom as a case study region where carbon codes, rather than environmental policies, have served to shape the agricultural soil carbon market. It explores innovative farmers' willingness to adopt soil health practices; interest in participating in soil carbon sequestration schemes; and expectations regarding their scope to derive benefits from the market. Data was collected through online questionnaires administered to 100 farmers and six private sector and civil society organisations. Results indicate farmers' adoption of practices does not necessarily translate into a willingness to adopt additional practices and/or an ability to engage with the carbon market. Moreover, there is, currently, a gap between farmers' expectations and market demands, as articulated by carbon standards. The paper adds to global literature on the agricultural soil carbon market by illustrating how descriptive case study research can enhance understanding of the opportunities and challenges associated with incentivising farmers' market participation. Furthermore, it generates insights of relevance for policymakers and practitioners globally by outlining how a temporary relaxation of carbon code rules could facilitate early and subsequent entrants’ engagement with the market; thereby kick-starting and supporting the growth and development of the market, and enhancing its transparency, robustness and integrity.

Fifty years after deep‐ploughing: Effects on yield, roots, nutrient stocks and soil structure

AbstractDeep‐ploughing far beyond the common depth of 30 cm was used more than 50 years ago in Northern Germany with the aim to break root‐restricting layers and thereby improve access to subsoil water and nutrient resources. We hypothesized that effects of this earlier intervention on soil properties and yields prevailed after 50 years. Hence, we sampled two sandy soils and one silty soil (Cambisols and a Luvisol) of which half of the field had been deep‐ploughed 50 years ago (soils then re‐classified as Treposols). The adjacent other half was not deep‐ploughed and thus served as the control. At all the three sites, both deep‐ploughed and control parts were then conventionally managed over the last 50 years. We assessed yields during the dry year 2019 and additionally in 2020, and rooting intensity at the year of sampling (2019), as well as changes in soil structure, carbon and nutrient stocks in that year. We found that deep‐ploughing improved yields in the dry spell of 2019 at the sandy sites, which was supported by a more general pattern of higher NDVI indices in deep‐ploughed parts for the period from 2016 to 2021 across varying weather conditions. Subsoil stocks of soil organic carbon and total plant‐available phosphorus were enhanced by 21%–199% in the different sites. Root biomass in the subsoil was reduced due to deep‐ploughing at the silty site and was increased or unaffected at the sandy sites. Overall, the effects of deep‐ploughing were site‐specific, with reduced bulk density in the buried topsoil stripes in the subsoil of the sandy sites, but with elevated subsoil density in the silty site. Hence, even 50 years after deep‐ploughing, changes in soil properties are still detectable, although effect size differed among sites.

A global dataset for the production and usage of cereal residues in the period 1997–2021

Crop residue management plays an important role in determining agricultural greenhouse gas emissions and related changes in soil carbon stocks. However, no publicly-available global dataset currently exists for how crop residues are managed. Here we present such a dataset, covering the period 1997–2021, on a 0.5° resolution grid. For each grid cell we estimate the total production of residues from cereal crops, and determine the fraction of residues (i) used for livestock feed/bedding, (ii) burnt on the field, (iii) used for other off-field purposes (e.g. domestic fuel, construction or industry), and (iv) left on the field. This dataset is the first of its kind, and can be used for multiple purposes, such as global crop modelling, including the calculation of greenhouse gas inventories, estimating crop-residue availability for biofuel production or modelling livestock feed availability.

The Evaluation of Carbon Farming Strategies in Organic Vegetable Cultivation

The urgent need to mitigate greenhouse gas (GHG) emissions has prompted the exploration of various strategies, including the adaptation of carbon farming practices, to achieve sustainability in agricultural systems. In this research, we assess the viability of carbon farming practices for organic vegetable growing in Europe. The study explores the potential benefits of these practices, including GHG emissions’ mitigation and improved soil health, biodiversity, and ecosystem services, while also acknowledging the need for further research to optimize implementation strategies and foster widespread adoption. However, the suitability and effectiveness of carbon farming practices in organic vegetable production systems remain uncertain. The analysis considers the measurement and estimation methods employed to assess changes in soil carbon stocks and the potential environmental and economic implications for farmers. Despite a substantial body of data demonstrating the sustainable attributes of carbon farming and its multifaceted advantages, a degree of hesitancy persists. Considering this, we propose undertaking a concise strengths, weaknesses, opportunities, and threats (SWOT) analysis to evaluate multiple aspects of carbon farming. The findings reveal that carbon farming practices can be viable and advantageous in organic vegetable production. Carbon farming practices, such as cover cropping, reduced tillage, compost application, and agroforestry, can significantly enhance the sustainability of organic farming systems. Implementing these practices can mitigate greenhouse gas emissions, improve soil health and fertility, and promote biodiversity conservation. Farmer education and support, policy measures, and continued research are crucial for maximizing the potential of these practices for a sustainable future. These practices also contribute to developing climate-friendly agricultural systems, promoting environmental resilience, and reducing the ecological footprint of organic vegetable production. However, further research is needed to optimize implementation strategies, address site-specific challenges, and foster widespread adoption of carbon farming practices in organic vegetable production.

Simulation Modeling of Forest Soil Respiration on the Example of Entic Carbic Podzol of Coniferous-Broad-Leaved Forest in the South of Moscow Region

The paper considers the results of calculations of the heterotrophic (HR) and total soil respiration for Entic Carbic Podzol under a coniferous-broad-leaved forest in the South of the Moscow region (54.89° N, 37.56° E), performed using the soil model Romul_Hum and a new version of the system of models EFIMOD3. The results of soil respiration modeling had a good correlation with the field measurement data. The Romul_Hum model simulates better the intensity of HR of the studied soil in wet than in dry years when it lightly overestimates the HR values. In the spatially detailed modeling of heterotrophic and root respiration using the EFIMOD3, the variability of carbon pools and fluxes associated with the distribution of the litterfall and hydrothermal conditions under the forest canopy was taken into account. The data obtained show that the intensity of HR at the beginning and middle of the growing season differs by about a factor of two, and HR values between different parts of the simulation site at the same time differ by more than 3.5 times. Spatial and temporal variability of the soil respiration affects the accuracy of estimates of C stocks in forest ecosystems. The used models are effective tools to analyze changes in soil carbon stocks, soil respiration, and carbon sink estimation in forest ecosystems, including tasks of forest management.

Quantifying impacts of forest fire on soil carbon in a young, intensively managed tree farm in the western Oregon Cascades

AbstractForest soils of the Pacific Northwest contain immense amounts of carbon (C). Increasing acreage burned by severe wildfire in the western Oregon Cascades threatens belowground C stocks. The objective of this research was to quantify the changes in soil C stocks, nitrogen (N) stocks, and relevant chemical and physical parameters after a severe wildfire in a young, intensively managed Pseudotsuga menziesii (Douglas‐fir) tree farm in the western Oregon Cascades. This longitudinal study was originally established to detect soil C changes after a harvest; therefore, it offers insight into long‐term soil C dynamics after compounding disturbances. Forest floor and 0–30 cm depth soil samples were collected for comparison before and after the fire and were then split into size fractions to assess the fire's effect on different grain sizes and forest floor compositions. Overall, soil C was approximately 40 Mg C ha−1 lower after the fire, equivalent to approximately 30% of soil C stocks. Of these decreases, two‐thirds were in the forest floor and one‐third were in the mineral soil. C stock losses were driven by changes in mass in every composite level. C concentration was unchanged in most levels while N concentration increased in certain levels. Losses extended further belowground than most previously studied soil C decreases from severe wildfire. The effects of wildfire on soil C stocks in industrial tree farms should be further explored to determine long‐term trajectories of soil C and N.