Changes In Carbon Stocks Research Articles

Sensitivity analysis of the FullCAM model: Context dependency and implications for model development to predict Australia's forest carbon stocks

In Australia, the Full Carbon Accounting Model (FullCAM) is used by the Australian Government for international reporting of greenhouse gas emissions and to predict carbon stock changes for carbon abatement projects. Consequently, over the last 20 years, it has been routinely applied at continental, regional and local scales, and has been subject to on-going development to improve its accuracy and representativeness. Given its importance, a sensitivity analysis could facilitate our understanding of model behaviour and aid the planning of future work and data collection. In particular, the sensitivity of a given model parameter is often context dependent such that it depends on the level of other parameters or variables.Key FullCAM parameters have generally been calibrated using data from empirical studies, with differing levels of confidence based on the sample size and data quality. The objective of this study was to apply a sensitivity analysis to examine (i) the sensitivity of FullCAM carbon stock outputs to its parameters and inputs, and how the sensitivity indices compare with the sample sizes used to calculate the respective parameters, (ii) the context dependency in terms of how the sensitivity varies with age, potential maximum biomass (a key FullCAM parameter), and disturbance severity or type, and (iii) to identify the implications for further development of FullCAM for woody vegetation systems.Of the 67 parameters tested, FullCAM carbon stock outputs were most sensitive to background mortality rates, age, potential maximum biomass, climate variability, age of maximum growth, decomposition or turnover parameters, and stand structure (regenerating or mature). The context dependency of the sensitivity analysis followed a consistent pattern depending on two main conditions, such that the sensitivity was higher when (i) the carbon stock was large and (ii) the parameter had a strong influence on that carbon stock. Several strong context dependencies occurred because the size of carbon stocks often vary through space and time within an ecosystem, and different processes (i.e. parameters) are more important at different times and locations. There was a strong context dependency in relation to age and potential maximum biomass, and FullCAM simulations indicated an interaction between fire disturbances and vegetation types. Lastly, background mortality was one of the least available inputs, but one to which FullCAM outputs were very sensitive. FullCAM was applied to show that the long-term contributions of low rates of background mortality to standing dead and debris C stocks were often as large as those from frequent (every 30 years) and intense harvesting and fire events because of the regular (annual) contribution of mortality and its accumulating influence of C stocks.

Cultivation of forage maize in boreal conditions – Assessment of trade-offs between increased productivity and environmental impact

The cultivation of whole crop forage maize (Zea mays L.) for cattle feed has a potential for increased forage yield while reducing nitrogen (N) fertilisation compared to perennial grass-based systems. However, the possible environmental trade-offs of forage maize cultivation remain unknown in the boreal region due to the short growing season which limits cultivation practices. The aim of this study was to compare the environmental impact of forage maize with more widely cultivated forage crops in Finland that include perennial silage grass mixtures and whole crop spring cereal harvested as silage. The use of plastic mulch film in forage maize cultivation was included in the assessment as well. A life cycle assessment (LCA) was conducted including impact categories for global warming potential; marine and freshwater eutrophication; terrestrial acidification; freshwater, marine and terrestrial ecotoxicity; land use; and fossil resource depletion. Additionally, soil organic carbon (SOC) stock changes under long-term cultivation of the studied forage crops were simulated with the C-TOOL and Yasso20 models with methodological comparisons. The only clear differences between the studied crops were that the land use was lower (−26–48%) for forage maize, and the freshwater eutrophication (+59–67%) and terrestrial acidification (+10–57%) were higher for perennial grasses compared with other forages. A risk for decreased SOC stock under continuous forage maize cultivation was observed. Forage maize could be used to supplement perennial grass cultivation without major associated environmental risks. Future research shall be conducted on the effect of forage choices on the environmental impact of boreal dairy milk production and on decreasing the current high uncertainty associated with nitrous oxide (N2O) emission factors and SOC stock modelling choices.

Spatial and Temporal Evolution and Prediction of Carbon Storage in Kunming City Based on InVEST and CA-Markov Model

Land use/cover change is an important driving factor for carbon stock changes in terrestrial ecosystems and affects the carbon cycle of the whole ecosystem. Taking Kunming City as a case study, based on the modified carbon density coefficient, this study analyzed the spatio-temporal characteristics of carbon storage changes in the terrestrial ecosystem under different land use scenarios from 2000 to 2020 and "three-line" constraints by coupling the carbon storage module of the InVEST model and CA-Markov model. The results showed that:① cultivated land, forest land, and grassland were the main types of land use in Kunming City, and land use transfer also occurred among the three types. ② From 2000 to 2020, the overall carbon storage in Kunming City was low in the south and high in the north, and the carbon storage decreased yearly with a cumulative loss of 5.27×106 t. The degradation of forest land and grassland was the main reason for the decrease in carbon storage. ③ From 2020 to 2030, the carbon storage of the four scenarios should decrease, and the decline in carbon storage in the inertia development scenario was the most obvious, which was mainly caused by the rapid expansion of construction land. The cultivated land protection scenario effectively slowed down the reduction in carbon storage compared with the inertia development scenario. The ecological protection scenario could enhance the carbon sequestration capacity of the study area, with carbon storage reaching 262.49×106 t, but could not effectively control the reduction in cultivated land area. The scenario of preventing urban expansion effectively inhibited the disorderly expansion of construction land and indirectly prevented further reduction in carbon storage. Therefore, the cultivated land protection scenario, ecological protection scenario, and urban expansion prevention scenario can be considered comprehensively in the study area, which could not only increase the carbon sink space of the study area but also ensure food and ecological security.

Forest carbon stock development following extreme drought-induced dieback of coniferous stands in Central Europe: a CBM-CFS3 model application

BackgroundWe analyze the forest carbon stock development following the recent historically unprecedented dieback of coniferous stands in the Czech Republic. The drought-induced bark-beetle infestation resulted in record-high sanitary logging and total harvest more than doubled from the previous period. It turned Czech forestry from a long-term carbon sink offsetting about 6% of the country's greenhouse gas emissions since 1990 to a significant source of CO2 emissions in recent years (2018–2021). In 2020, the forestry sector contributed nearly 10% to the country's overall GHG emissions. Using the nationally calibrated Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) at a regional (NUTS3) spatial resolution, we analyzed four scenarios of forest carbon stock development until 2070. Two critical points arise: the short-term prognosis for reducing current emissions from forestry and the implementation of adaptive forest management focused on tree species change and sustained carbon accumulation.ResultsThis study used four different spruce forest dieback scenarios to assess the impact of adaptive forest management on the forest carbon stock change and CO2 emissions, tree species composition, harvest possibilities, and forest structure in response to the recent unprecedented calamitous dieback in the Czech Republic. The model analysis indicates that Czech forestry may stabilize by 2025 Subsequently, it may become a sustained sink of about 3 Mt CO2 eq./year (excluding the contribution of harvested wood products), while enhancing forest resilience by the gradual implementation of adaptation measures. The speed of adaptation is linked to harvest intensity and severity of the current calamity. Under the pessimistic Black scenario, the proportion of spruce stands declines from the current 43–20% by 2070, in favor of more suited tree species such as fir and broadleaves. These species would also constitute over 50% of the harvest potential, increasingly contributing to harvest levels like those generated by Czech forestry prior to the current calamity. The standing stock would only be recovered in 50 years under the optimistic Green scenario.ConclusionThe results show progress of adaptive management by implementing tree species change and quantify the expected harvest and mitigation potential in Czech forestry until 2070.

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.

Assessment of land use cover changes, carbon sequestration and carbon stock in dry temperate forests of Chilas watershed, Gilgit-Baltistan

Abstract Land use and land cover change are affecting the global environment and ecosystems of the different biospheres. Monitoring, reporting and verification (MRV) of these changes is of utmost importance as they often results in several global environmental consequences such as land degradation, mass erosion, habitat deterioration as well as micro and macro climate of the regions. The advance technologies like remote sensing (RS) and geographical information system (GIS) are helpful in determining/ identifying these changes. In the current study area, changes in carbon stocks, notably in forest areas, are resulting in considerable dynamics of carbon stocks as a result of climate change and carbon sequestration. This study was carried out in the Diamer district of the Gilgit Baltistan (GB) Pakistan to investigate the change in cover change/land use change (particularly Forest Land use) as well as carbon sequestration potential of the forests in the district during almost last 25years. The land cover, temporal Landsat data (level 1, LIT) were downloaded from the USGS EROS (2016), for 1979-1989, 1990-2000 and 2001-2012. Change in land uses, particularly forest cover was investigated using GIS techniques. Forest inventory was carried out using random sampling techniques. A standard plot of size 0.1 ha (n=80) was laid out to determine the tree density, volume, biomass and C stocks. Simulation of C stocks was accomplished by application of the CO2FIX model with the data input from inventory. Results showed a decrease in both forest and snow cover in the region from 1979-2012. Similarly decrease was seen in tree volume, tree Biomass, dynamics of C Stocks and decrease was in occur tree density respectively. It is recommended we need further more like project such as BTAP (Billion Tree Afforestation Project) and green Pakistan project to increase the forest cover, to control on land use change, protect forest ecosystem and to protect snow cover.

Metagenomic insights into microbial diversity and carbon cycling related genes along the elevational gradient in an arid mountain ecosystem

Understanding the elevational patterns of soil microbial carbon (C) metabolic potentials is instrumental for predicting changes in soil organic carbon (SOC) stocks in the face of climate change. However, such patterns remain uncertain in arid mountain ecosystems, where climosequences are quite different from other ecosystems. To address this gap, this study investigated the distribution determinants of microbial communities, C-cycling functional genes, and SOC fractions along the elevational gradient (1 707−3 548 m, a mean annual precipitation (MAP) range of 38 to 344 mm) of the north slope of Central Kunlun Mountain, using a metagenomic approach. Results showed that elevation significantly influenced the α-diversity (Shannon index) and composition of microbial communities as well as the C-cycling functional genes. The α-diversity of microbial taxonomy and C-cycling functional genes linearly increased with the increase in MAP along the elevational gradient. The elevational patterns of genes encoding glycoside hydrolases and glycosyltransferases (GTs) were mainly driven by electrical conductivity (EC), mean average temperature (MAT), MAP, and plant diversity. Furthermore, mineral-associated organic carbon (MAOC), particulate organic carbon (POC), and their sum generally increased with elevation. However, the MAOC/POC ratio followed a unimodal pattern, suggesting greater stability of the SOC pool in the mid-elevation regions. This unimodal pattern was likely influenced by the abundance of Actinobacteria and genes encoding GTs and carbohydrate esterases (CEs) and threshold effects of EC and MAT. In summary, our findings indicate that the distribution patterns of microbial communities and C-cycling functional genes along the elevational gradient in an arid ecosystem are distinct from those of regions with higher MAP, facilitating the prediction of climate change effects on SOC metabolism under more arid conditions. Soil salinity, plant diversity, precipitation, and temperature are the main regulatory factors of microbial C metabolism processes, and they potentially play a central role in mediating SOC pool stability.

Space-time mapping of soil organic carbon stock and its local drivers: Potential for use in carbon accounting

The measurement and tracking of changes in soil organic carbon (SOC) stocks and its underpinning drivers are important in greenhouse gas accounting and carbon trading schemes. While repeated direct measurement of a location over time is the ‘gold standard’ for SOC stock change estimation, this is currently unfeasible at scale due to sample collection and analysis costs. Here, we used a data-driven, space–time digital soil mapping modelling approach (ST-DSM) coupled with an interpretive machine learning (IML) technique to both predict and quantify the relative contributions of covariates to annual SOC stocks and their uncertainty at 0–30 cm depth and at a 90 m spatial resolution for Australia between 1990 and 2018. A quantile regression forest model was calibrated using data from a datacube comprising of SOC stock values collected over the prediction years and a suite of dynamic and static environmental covariates. The evaluation of the ST-DSM model on a test set was satisfactory. Long-term annual mean (Mg C/ha), and total (Pg C) topsoil SOC stock were 37.6 (12.3 – 101.1, 90 % PI) and 28.3 (9.25 – 83.1, 90 % PI) respectively. The mean annual rate of SOC stock change over the Australian continent was 0.11 (±0.22) Mg C/ha yr−1 and the total net change was 23.5 Tg C yr−1, indicating Australia’s soils were a net sink of SOC over the 29-year period. However, SOC stocks declined in the montane ecoregion, a great concern given its fragility and high SOC stock. The long-term mean fraction of photosynthetic vegetation was the most important individual local contributor to SOC stock prediction in many parts of Australia. The aggregated effect of covariates based on the soil forming factors indicates vegetation as the principal local driver of SOC stock across most of the Australian continent, followed by climate. The evaluation of our results against independent, temporally paired field data and estimates from a nationally accepted SOC process-based model yielded promising results. Our approach demonstrates the use of readily available and inexpensive covariates to estimate SOC stock changes, as well as the underlying drivers over a larger area but at a spatial resolution suitable for decision making. This approach presents a new monitoring and verification possibility for carbon projects and national carbon accounting especially with the growing number of existing profile observations in soil databases.

The changes in soil organic carbon stock and quality across a subalpine forest successional series

Soil organic carbon (SOC) affects the function of terrestrial ecosystem and plays a vital role in global carbon cycle. Yet, large uncertainty still existed regarding the changes in SOC stock and quality with forest succession. Here, the stock and quality of SOC at 1-m soil profile were investigated across a subalpine forest series, including shrub, deciduous broad-leaved forest, broadleaf-conifer mixed forest, middle-age coniferous forest and mature coniferous forest, which located at southeast of Tibetan Plateau. The results showed that SOC stock ranged from 9.8 to 29.9 ​kg⋅m−2, and exhibited a hump-shaped response pattern across the forest successional series. The highest and lowest SOC stock was observed in the mixed forest and shrub forest, respectively. The SOC stock had no significant relationships with soil temperature and litter stock, but was positively correlated with wood debris stock. Meanwhile, the average percentages of polysaccharides, lignins, aromatics and aliphatics based on FTIR spectroscopy were 79.89%, 0.94%, 18.87% and 0.29%, respectively. Furthermore, the percentage of polysaccharides exhibited an increasing pattern across the forest successional series except for the sudden decreasing in the mixed forest, while the proportions of lignins, aromatics and aliphatics exhibited a decreasing pattern across the forest successional series except for the sudden increasing in the mixed forest. Consequently, the humification indices (HIs) were highest in the mixed forest compared to the other four successional stages, which means that the SOC quality in mixed forest was worse than other successional stages. In addition, the SOC stock, recalcitrant fractions and HIs decreased with increasing soil depth, while the polysaccharides exhibited an increasing pattern. These findings demonstrate that the mixed forest had higher SOC stock and worse SOC quality than other successional stages. The high proportion of SOC stock (66% at depth of 20–100 ​cm) and better SOC quality (lower HIs) indicate that deep soil have tremendous potential to store SOC and needs more attention under global change.

The Carbon Stock Change of Vegetation and Soil in the Forest Due to Forestry Projects

The Carbon Stock Change of Vegetation and Soil in the Forest Due to Forestry Projects

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.

Cost Valuation and Climate Mitigation Impacts of Forest Management: A Case Study from Piatra Craiului National Park, Romania

With the intensification of the effects of climate change, the urgent need to address their drivers, especially greenhouse gas emissions, has become essential. In this context, forests offer a robust solution, with their potential to store and mitigate carbon emissions. However, striking a balance is critical given the significant economic contribution of the forestry and wood-based industries, which account for about 5% of Romania’s GDP and employ 6% (around 300 thousand) of its active workforce. This study, conducted in the Piatra Craiului National Park located in Romania’s Southern Carpathians, we utilize the EFISCEN application to generate three distinct 50-year forest evolution scenarios based on harvest intensity, namely Business As Usual (BAU), Maximum Intensity (MAX), and No Harvest (MIN), on two historical different managed forests, i.e., conservation and production. The study aims to guide forest owners in decision making with scenario modeling tools, with the objectives of assessing the forest carbon sequestration potential and evaluating the economic feasibility. In the most probable scenario, the BAU scenario, the growing stock increases from 2.6 million m3 to 3.8 million m3 over 50 years, with a more than 40% increase. Comparing the carbon stock change for all tree harvest scenario types indicates that the MIN scenario has the highest carbon sink capacity in the next 50 years; the BAU scenario is a well-balanced option between carbon sink and wood provision and has an optimal EUR 3.7 million in annual revenue. The MAX scenario can boost the growth and increase the annual revenue from wood by 35% but is effective only for a short time and thus has the smallest calculated revenue in time. Achieving a win–win relationship between carbon sequestration and wood supply is imperative, as well as good planning and scenarios to contribute to climate mitigation and also as provisions for local communities and to sustain the local economy.

The role of fiscal instruments in the implementation of low-carbon agriculture

Purpose. The study purpose is to determine the aspects for improving the fiscal toolkit as an economic lever for regulating agricultural land use with the optimized approach to the selection of areas of introduction of the low-carbon development for the formation of organizational and economic management conditions towards the ensuring of restoration and preservation of agricultural resource potential.
 Methodology / approach. In this work, we used the following research methods: monographic, statistical analysis, graphic, correlation and regression analysis. The national and international documents of legal framework for regulating the processes of agricultural land use, materials of the State Statistics Service of Ukraine were used.
 Results. Based on the ecological and economic efficiency analysis of agricultural land use, the priority of obtaining profits in contrast to the problems of the restoration and preservation of the agricultural resource potential was demonstrated, thanks to which Ukraine took the lead in many commodity crops export. The soil fertility decline is a reason of formed threat to agroecological and food security. Based on the assessment of the nitrogen balance flows, the amount of removal of nutrients from the soil cover was estimated.
 Originality / scientific novelty. The expediency of using an improved tax instrument for land use as an economic lever for the formation of organizational and economic conditions of management with a focus on the introduction of the principles of the green economy is substantiated. This improvement consists in the correction factor proposed for the first time to the calculated volumes of tax collections. This coefficient allows taking into account the characteristics of the land use effectiveness in combination with the coefficients of carbon stock changes of the internationally recognized methodology UN Intergovernmental Panel on Climate Change (IPCC). Based on the improvement of the target agroecological zoning approach (on the example of the Odesa region), an approach to establishing the priority of land plots from the point of view of the perspective of introducing low-carbon land use is proposed.
 Practical value / implications. The proposed approach opens the possibility to optimize efforts to introduce low-carbon land use and therefore to restore and preserve agro-resource potential. The national crop production competitiveness is ensured by this. Therefore, this approach can be taken as a basis for the introduction of the latest green economy tools for the agricultural land use sector at the level of territorial communities.

Changes in soil organic carbon stocks and its physical fractions along an elevation in a subtropical mountain forest

Soil microorganisms are the drivers of soil organic carbon (SOC) mineralization, and the activities of these microorganisms are considered to play a key role in SOC dynamics. However, studies of the relationship between soil microbial carbon metabolism and SOC stocks are rare, especially in different physical fractions (e.g., particulate organic carbon (POC) fraction and mineral-associated organic carbon (MAOC) fraction). In this study, we investigated the changing patterns of SOC stocks, POC stocks, MAOC stocks and microbial carbon metabolism (e.g., microbial growth, carbon use efficiency and biomass turnover time) at 0–20 cm along an elevational gradient in a subtropical mountain forest ecosystem. Our results showed that SOC and POC stocks increased but MAOC stocks remained stable along the elevational gradient. Soil microbial growth increased while microbial turnover time decreased with elevation. Using structural equation modeling, we found that heightened microbial growth is associated with elevated POC stocks. Moreover, MAOC stocks positively correlate with microbial growth but show negative associations with both POC stocks and soil pH. Overall, the increase in SOC stocks along the elevational gradient is primarily driven by changes in POC stocks rather than MAOC stocks. These findings underscore the importance of considering diverse soil carbon fractions and microbial activities in predicting SOC responses to elevation, offering insights into potential climate change feedbacks.

Changes in Soil Organic Carbon Stocks Due to Land Use Changes in the Extended São Francisco River Basin

As the largest carbon reservoir in terrestrial ecosystems, soils play a critical role in food production, mitigation and adaption to climate change, and sustainability of agroecosystems. In this context, the aim of this study is to estimate variations in soil carbon stocks resulting from land use and management changes in different biomes that compose the Bacia Estendida do Rio São Francisco (BESF - Extended São Francisco River Basin), between 1985 and 2017. For this, remote sensing data and information from the IBGE agriculture and livestock census were used, in addition to emission factors to estimate soil organic carbon (SOC) changes. The results indicate that BESF had about 5.70 million ha degraded in the analyzed period, in addition to an increase of 0.72 Tg C year-1 in SOC stocks. The sub-medium São Francisco River basin recorded the highest SOC gain, with an increase of 0.54 Tg C ha-1; on the other hand, the sub-medium São Francisco River sub-basin had the greatest SOC losses, with an estimated reduction of 0.07 Tg C year-1. In short, this study provides important evidence on changes in SOC stocks in the region, emphasizing the importance of native vegetation conversion to agriculture and livestock systems under sustainable soil management for mitigating greenhouse gas emissions and maintaining soil quality.

Effects of Drainage on Carbon Stock in Hemiboreal Forests: Insights from a 54-Year Study

In the Northern Hemisphere, forests play an important role in carbon storage. During the past few decades in the eastern Baltic and Nordic regions, forest drainage has been a common occurrence, which also has an effect on carbon stock. Most of the studies on this issue were carried out in boreal zones and were focused on short-term effects. Thus, our aim was to evaluate the long-term (after 54 years) effect of drainage on carbon stock (CS) changes in organic soil (Fibric histosols) in hemiboreal forests. Three forest types were selected in drained (Myrtillosa turf. mel (Mmel)) and undrained (Caricoso–phragmitosa (CP) and Sphagnosa (Sph)) parts of the same area. Surface level changes, soil penetration resistance, and soil and tree biomass carbon stock were assessed to evaluate the drainage effect. Drainage caused an average surface level drop of 25 cm, but did not deplete the soil carbon pool, resulting in significantly and substantially higher (2 to 6 times) tree biomass carbon stock. The drainage of organic soils in managed wet forests leads to an increased long-term contribution to climate change mitigation, thus such areas should be established or maintained in conjunction with areas that maximize other ecosystem services to ensure the sustainability of forest landscapes.

Mind the gap: reconciling tropical forest carbon flux estimates from earth observation and national reporting requires transparency

BackgroundThe application of different approaches calculating the anthropogenic carbon net flux from land, leads to estimates that vary considerably. One reason for these variations is the extent to which approaches consider forest land to be “managed” by humans, and thus contributing to the net anthropogenic flux. Global Earth Observation (EO) datasets characterising spatio-temporal changes in land cover and carbon stocks provide an independent and consistent approach to estimate forest carbon fluxes. These can be compared against results reported in National Greenhouse Gas Inventories (NGHGIs) to support accurate and timely measuring, reporting and verification (MRV). Using Brazil as a primary case study, with additional analysis in Indonesia and Malaysia, we compare a Global EO-based dataset of forest carbon fluxes to results reported in NGHGIs.ResultsBetween 2001 and 2020, the EO-derived estimates of all forest-related emissions and removals indicate that Brazil was a net sink of carbon (− 0.2 GtCO2yr−1), while Brazil’s NGHGI reported a net carbon source (+ 0.8 GtCO2yr−1). After adjusting the EO estimate to use the Brazilian NGHGI definition of managed forest and other assumptions used in the inventory’s methodology, the EO net flux became a source of + 0.6 GtCO2yr−1, comparable to the NGHGI. Remaining discrepancies are due largely to differing carbon removal factors and forest types applied in the two datasets. In Indonesia, the EO and NGHGI net flux estimates were similar (+ 0.6 GtCO2 yr−1), but in Malaysia, they differed in both magnitude and sign (NGHGI: -0.2 GtCO2 yr−1; Global EO: + 0.2 GtCO2 yr−1). Spatially explicit datasets on forest types were not publicly available for analysis from either NGHGI, limiting the possibility of detailed adjustments.ConclusionsBy adjusting the EO dataset to improve comparability with carbon fluxes estimated for managed forests in the Brazilian NGHGI, initially diverging estimates were largely reconciled and remaining differences can be explained. Despite limited spatial data available for Indonesia and Malaysia, our comparison indicated specific aspects where differing approaches may explain divergence, including uncertainties and inaccuracies. Our study highlights the importance of enhanced transparency, as set out by the Paris Agreement, to enable alignment between different approaches for independent measuring and verification.

Testing the feasibility of quantifying change in agricultural soil carbon stocks through empirical sampling

There is disagreement about the potential for regenerative management practices to sequester sufficient soil organic carbon (SOC) to help mitigate climate change. Measuring change in SOC stocks following practice adoption at the grain of farm fields, within the extent of regional agriculture, could help resolve this disagreement. Yet sampling demands to quantify change are considered infeasible primarily because within-field variation in stock sizes is thought to obscure accurate quantification of management effects on incremental SOC accrual. We evaluate this ‘infeasibility assumption’ using high-density (e.g., 0.1 ha sample–1), within-field, sampling data from 45 cropland fields inventoried for SOC. We explore how more typical within-field sampling densities, as well as field numbers and magnitude of simulated change in SOC stocks, impacts the ability to accurately quantify management effects on SOC change. We find that (1) stock change estimates for individual fields are inaccurate and variable, where marked losses and gains in SOC stocks are frequently estimated even when no change has occurred. Higher sampling densities (e.g., 1.2 versus 4.0 ha sample–1) narrow the range of estimated stock changes but inaccuracies remain large. (2) The accuracy of stock change estimates at the project level (i.e., multiple fields) were similarly sensitive to sampling density. In contrast to individual fields, however, higher sampling densities, as well as a greater number of fields (e.g., 30), generated robust and accurate, mean project-level estimates of carbon accrual, with ∼ 80 % of the estimates falling within 20 % of the simulated stock change. Yet such monitoring designs do not account for dynamic baselines, which necessitates measurement of stock changes in control, non-regenerative fields. We find (3) that higher sampling densities (e.g., 1.2 versus 4.0 ha sample–1), field numbers (e.g., 30 versus 10 pairs of fields), and magnitudes of simulated SOC stock change (+3 and +5 versus +1 Mg C ha−1 10 y–1) are then collectively required to make accurate estimates of management effects on stock change at the project level. The simulated effect sizes that could be consistently detected under these conditions included rates of SOC accrual considered achievable and meaningful for climate mitigation (e.g., 3 Mg C ha−1 10 y–1), with field numbers and sampling densities that are reasonable given current sampling methods. Our findings reveal the potential to use empirical approaches to accurately quantify, at project scales, SOC stock responses to practice change. We provide recommendations for data that government, farmer and corporate entities should measure and share to build confidence in the effects of regenerative practices, freeing the SOC debate from overreliance on theory and data collected at scales mismatched with agricultural management.

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.