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• Litter processing by fauna was studied along successional gradient in rain forest. • Litter removal from soil surface is accelerated by soil fauna. • Soil fauna promote C storage in mineral soil. • Fauna reduced overall loss of C from the mesocosms. Mesocosm studies in temperate soils indicate that soil fauna may promote accumulation of C in mineral soil. To test if this effect apply also in tropics we used field mesocosms that were either accessible or inaccessible to soil fauna. To explore potential interaction with traditional land use we locate these mesocosms along a succession gradient following traditional swidden agriculture in the lowland tropical rain forest of Papua New Guinea. Soil fauna densities did not show any significant changes along the succession gradient. Litter fall in primary forest was significantly higher than in younger succession stages. Litter stock on the soil surface follows the same pattern as litter fall. Litter stock was a few percent higher than annual litter fall suggests that litter removal from soil surface takes slightly over one year. Our Mesocosm experiment shows the same speed of litter removal (about one year). Litter removal from surface and its incorporation of organic matter into mineral soil is faster in the fauna treatment compared to the non-fauna treatment. Overall loss of C from the system was higher when fauna was absent. Fauna reduced overall loss of C from the soil in average for more then 40%. In conclusion soil fauna play important role in organic matter transformation and soil C storage in tropical ecosystem. Fauna removal substantially reduce overall soil C storage. [ABSTRACT FROM AUTHOR]

Poplars grown in short rotation coppice on agricultural land are a promising bioenergy crop. This study aimed to evaluate the soil organic matter (SOM) quality and viable microbial consortium under six-years-old poplar (Populus maximowiczii) and under wheat (Triticum aestivum) at a test site in central Germany. The SOM molecular composition and stability was determined by pyrolysis-field ionization mass spectrometry (Py-FIMS). The microbial consortium was assessed in terms of microbial phospholipid fatty acid (PLFA) profiles. Py-FIMS and the PLFAs agreed in showing crop-specific differences in the SOM quality and in the associated microbial communities. Higher proportions of carbohydrates, long-chained fatty acids, sterols and suberins at the expense of N-containing compounds under poplar than under wheat were associated with lower concentrations of microbial PLFAs in the organic matter. A higher ratio of total fungal to bacterial (f/b) PLFAs, a lower ratio of Gram-positive to Gram-negative bacterial PLFAs and lower biomass of arbuscular mycorrhizal fungi in the organic matter were revealed under poplar than under wheat. Lower N- and increased C-availability in the SOM promoted fungal vs. bacterial colonization, increased the SOM stability by a lower decomposability and caused SOM accumulation under poplar.

The study was the first attempt to identify the habitat use pattern of red-crowned cranes (Grus japonensis) around the demilitarized zone (DMZ) by overlapping coordinates with the land cover classification (LCC). Daily habitat use pattern was highly different (P = 0.000) between daytime (06:00⁻18:00) and nighttime (18:00⁻06:00). Cranes in Cheolwon used agricultural paddies more frequently in the daytime (P = 0.002), and forest areas at night and this indicated that cranes presumably use rice paddies for feeding and forests for resting, respectively. Cranes night time in Paju used wetlands more often than random expectation based on the available wetland surface area (P = 0.017). This indicated a different habitat use pattern between coastal (Paju) and inland (Cheolwon) areas. Securing agricultural paddies is important for providing crucial areas for feeding, and forests should be important for rest during the night time in Cheolwon, which support crane populations during their wintering migration in Korea.

Organo-mineral complexes (OMCs) are referred to as biogeochemical black boxes and are widely thought to contribute to the long-term preservation of organic matter. However, the history and potential research directions of OMC research, as well as the deep applications of OMCs, have not been fully investigated. We conducted a comprehensive bibliometric study based on the Science Citation Index core database publications from 1959 to 2020 to fill this research gap in OMC studies. The results showed that a total of 751 publications involving OMCs (OMCPs) were published. There was a significant positive correlation between the frequency of international associations and the number of OMCPs. A dendrogram containing six categories and 130 keywords was constructed to represent the research content of OMCPs. In particular, the keyword co-occurrence analysis and a laboratory-scale practice jointly verified the feasibility of using silicate minerals and manure compost to produce synthetic OMCs. The life span prediction analysis revealed that the research on OMCs is in the climax stage, while the current number of studies is still less than 50% of the saturation amount. The two most potentially promising research directions are the use of OMCs in agriculture and pollutant control, which currently account for less than 30% and 25% of the saturation amount, respectively. This report clarified the research gap and predicted the development trend of OMC research using bibliometrics for the first time, and highlighted the importance of OMCs in improving agricultural production while stabilizing pollutant migration in agricultural soil. [Display omitted] • Researches on organo-mineral complexes (OMCs) are now in the climax stage. • A total of 130 keywords in six categories were involved in the OMC studies. • OMCs have good potential in agricultural and pollution control applications. • Keyword analysis and a practice proved the feasibility of OMCs in an application. • Publications on OMCs were reviewed using bibliometrics for the first time. [ABSTRACT FROM AUTHOR]

Agricultural management practices are frequently non conservative and can lead to substantial loss of soil organic carbon and soil fertility, but for many regions in Africa the knowledge is very limited. To study the effect of local agricultural practices on soil organic carbon content and to explore effective ways to increase soil carbon storage, field experiments were conducted on an upland rice soil (Lixisol) in northern Benin in West Africa. The treatments comprised two tillage systems (no-tillage, and manual tillage), two rice straw managements (no rice straw, and rice straw mulch at 3 Mg ha −1 ) and three nitrogen fertilizer levels (no nitrogen, 60 kg ha −1 , 120 kg ha −1 ). Phosphorus and potassium fertilizers were applied to be non-limiting at 40 kg P 2 O 5 ha −1 and 40 kg K 2 O ha −1 per cropping season. Heterotrophic respiration was higher in manual tillage than no-tillage, and higher in mulched than in non-mulched treatments. Under the current management practices (manual tillage, with no residue and no nitrogen fertilization) in upland rice fields in northern Benin, the carbon added as aboveground biomass and root biomass was not enough to compensate for the loss of carbon from organic matter decomposition, rendering the upland rice fields as net sources of atmospheric CO 2 . With no-tillage, 3 Mg ha −1 of rice straw mulch and 60 kg N ha −1 , the soil carbon balance was approximately zero. With no other changes in management practices, an increase in nitrogen level from 60 kg N ha −1 to 120 kg N ha −1 resulted in a positive soil carbon balance. Considering the high cost of inorganic nitrogen fertilizer and the potential risk of soil and air pollution often associated with intensive fertilizer use, implementation of no-tillage combined with application of 3 Mg ha −1 of rice straw mulch and 60 kg N ha −1 could be recommended to the smallholder farmers to compensate for the loss of carbon from organic matter decomposition in upland rice fields in northern Benin. [ABSTRACT FROM AUTHOR]

Agriculture is an important source of greenhouse gases, but can also be a significant sink. Nitrogen fertilization is effective in increasing agricultural production and carbon storage. We explored the effects of different rates of nitrogen fertilization on biomass, carbon density, and carbon sequestration in fields under the cultivation of Jerusalem artichoke as well as in soil in a coastal saline zone for two years. Five nitrogen fertilization rates were tested (in g urea m − 2 ): 4 (N1), 8 (N2), 12 (N3), 16 (N4), and 0 (control, CK). The biomass of different organs of Jerusalem artichoke during the growth cycle was significantly higher in N2 than the other treatments. Under different nitrogen treatments, carbon density in organs of Jerusalem artichoke ranged from 336 to 419 g C kg − 1 . Carbon sequestration in Jerusalem artichoke was higher in treatments with nitrogen fertilization compared to the CK treatment. The highest carbon sequestration was found in the N2 treatment. Soil carbon content was higher in the 0–10 cm than 10–20 cm layer, with nitrogen fertilization increasing carbon content in both soil layers. The highest soil carbon sequestration was measured in the N2 treatment. Carbon sequestration in both soil and Jerusalem artichoke residue was increased by nitrogen fertilization depending on the rates in the coastal saline zone studied. [ABSTRACT FROM AUTHOR]

Coastal dunes support biodiverse habitats of conservation interest and provide other essential but often overlooked benefits to society, such as carbon sequestration, thanks to their high soil carbon accumulation rates. The recently established coastal dune Natura 2000 network in the Italian Adriatic coast aims at protecting dune habitats diversity, yet its capacity to provide other ecosystem services, and the potential trade-offs with biodiversity provision have so far not been evaluated. In this paper we conduct this analysis for a key ecosystem service: carbon storage and sequestration. We i) quantify soil carbon stocks and sequestration within four coastal dune EU habitat types along the Adriatic Natura 2000 network; ii) upscale these data to create an inventory of carbon stocks for all dune Natura 2000 sites in the study area; iii) collate biodiversity data of the selected EU habitat types using plant diversity measures as surrogates of coastal dune biodiversity and iv) explore the trade-offs between carbon storage and biodiversity value for the selected habitats. Italian Adriatic coastal dune Natura 2000 sites sequester 4998 t of CO 2 e per year, with the majority in wooded dunes. Wooded dunes showed significantly higher soil carbon density than the other dune habitats, and had a much greater area, but they were characterized by lower species richness. By contrast, the endangered fixed dunes, which survive in few residual patches along the study area, showed the highest plant diversity for both total species richness and dune focal species, but had a much lower carbon density and extent. Although further analyses of additional services would be desirable for a more comprehensive assessment, these findings suggest that conservation actions should favor restoration of the natural dune zonation, since it guarantees both dune species diversity and carbon storage. The carbon stocks and EU habitat type extents produced in this study constitute the first systematic inventory for dune systems in the Mediterranean. [ABSTRACT FROM AUTHOR]

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In grassland, introduction of legume potentially can play a significant role in increasing soil carbon (C) and nitrogen (N) storage through increasing biomass C input. It has been reported that grass–legume ratio (GLR) is important in assessing benefits of grass–legume mixtures, however, little is known about how GLR affects soil C and N storage. As an effort to understand the effects and mechanisms of GLR on soil carbon and nitrogen storage, biological nitrogen fixation (BNF) by legumes, and changes in C and N storage in plants and soil were examined under swards with different densities of grasses and legumes over 4 years in a temperate steppe grassland. Results showed that total N storage in 0–40 and overall 0–150 cm soil depths varied as GLR changed, reaching peak values when the GLR was equivalent to 1:1. Increased relative legume abundance significantly enhanced soil C storage in both 0–40 and 0–150 cm soil depths, which was primarily attributed to an increase of aboveground biomass C. Soil organic C and total N varied with GLR changes, leading to stoichiometric shifts in soil C:N ratios, possibly influencing soil C storage through changing plant community structure and soil biochemistry. It is suggested that introducing legumes in steppe grasslands with a GLR of 1:1 could increase resources use efficiency and improve the sustainability of the environment. [ABSTRACT FROM AUTHOR]

Accounting for one quarter of China’s land area, the endorheic Shiyang River basin is a vast semi-arid to arid region in China’s northwest. Exploring the impact of changes in land use on this arid area’s carbon budget under global warming is a key component to global climate change research. Variation in the region’s soil carbon storage due to land use changes occurring between 1973 and 2012 was estimated. The results show that land use change has a significant impact on the soil carbon budget, with soil carbon storage having decreased by 3.89 Tg between 1973 and 2012. Grassland stored the greatest amount of soil carbon (114.34 Mg ha−1), whereas considerably lower carbon storage occurred in woodland (58.53 Mg ha−1), cropland (26.75 Mg ha−1) and unused land (13.47 Mg ha−1). Grasslands transformed into cropland, and woodlands degraded into grassland have substantially reduced soil carbon storage, suggesting that measures should be adopted to reverse this trend to improve soil productivity.

Biodegradable mulch film potentially offers an encouraging alternative to conventional (petroleum-based) plastic films. Since biodegradable films are more susceptible to rapid degradation, more microplastics (MPs) are likely to be generated than conventional films within the same time frame, probably leading to more severe MPs pollution and associated effects. However, the effect of biodegradable mulch film residues and associated MPs pollution on plant-soil health remains uncertainty. Here, we evaluated the potential effect of bio-MPs pollution on soil carbon (C) and nutrient (i.e., N and P) cycling, soil biology (microorganisms and mesofauna), and plant health, as these are crucial to agroecosystem functioning and the delivery of key ecosystem services. Unlike the inert (and therefore recalcitrant) C contained within petroleum-based MPs, at least 80% of the C from bio-MPs is converted to CO 2 , with up to 20% immobilized in living microbial biomass (i.e., < 0.05 t C ha−1). Although biodegradable films are unlikely to be important in promoting soil C storage, they may accelerate microbial biomass turnover in the short term, as well as CO 2 production. Compared to conventional MPs, bio-MPs degradation is more pronounced, thereby inducing greater alterations in microbial diversity and community composition. This may further alter N 2 O and CH 4 emissions, and ultimately resulting in unpredictable consequences for global climate warming. The extent to which this may occur, however, has yet to be shown in either laboratory or field studies. In addition, bio-MPs have a large chance of forming nanoplastics, potentially causing a stronger toxic effect on plants relative to conventional MPs. Consequently, this would influence plant health, crop productivity, and food safety, leading to potential health risks. It is unclear, however, if these are direct effects on key plant processes (e.g. signaling, cell expansion) or indirect effects (e.g. nutrient deficiency or acidification). Overall, the question as to whether biodegradable mulch films offer a promising alternative to solve the conventional plastic legacy in soil over the long term remains unclear. [Display omitted] • Bioplastics (Bio-MPs) are unlikely to be important in promoting soil C storage. • Bio-MPs act as labile C sources to stimulate microbial growth and soil N and P cycling. • Bio-MPs are much easier to form nanoplastics and cause stronger toxic to plants. • Uncertainty of bio-MPs pollution remains on plant-soil health. [ABSTRACT FROM AUTHOR]

Since agriculture directly contributes to global anthropogenic greenhouse gas (GHG) emissions, integrating trees into agricultural landscapes through agroforestry systems is a viable adaptive strategy for climate change mitigation. The objective of this study was to evaluate the carbon (C) sequestration and financial benefits of C sequestration according to Quebec's Cap-and-Trade System for Greenhouse Gas Emissions Allowances (C & T System) or the Système de plafonnement et d'échange de droits d'émission de gaz à effet de serre du Québec (SPEDE) program for two experimental 10-year-old tree-based intercropping (TBI) systems in southern Quebec, Canada. We estimated total C stored in the two TBI systems with hybrid poplar and hardwoods and adjacent non-TBI systems under agricultural production, considering soil, crop and crop roots, litterfall, tree and tree roots as C stocks. The C sequestration of the TBI and adjacent non-TBI systems were compared and the market value of the C payment was evaluated using the net present value (NPV) approach. The TBI systems had 33% to 36% more C storage than adjacent non-TBI systems. The financial benefits of C sequestration after 10 years of TBI practices amounted to of $2,259-$2,758 CAD ha 1 and $1,568-$1,913 CAD ha 1 for St. Edouard and St. Paulin sites, respectively. We conclude that valorizing the C sequestration of TBI systems could be an incentive to promote the establishment of TBI for the purpose of GHG mitigation in Quebec, Canada. [ABSTRACT FROM AUTHOR]

Coffee agroforestry systems (CAS) are considered as a climate change mitigation option through carbon sequestration. However, most studies on CAS have concentrated on management and productivity of the coffee plants with little known about the soil organic carbon (SOC) stocks. We conducted a study to quantify and compare the SOC stocks among Coffea arabica L. (Arabica coffee), Coffee canephora Pierre ex Froehn (Robusta coffee) agroforestry systems and Coffee monoculture (coffee monocrops) in Uganda. Soil samples were collected at 0–15 cm and 15–30 cm and tested using routine soil testing procedures. We found that there was higher SOC under CAS than coffee monocrops. When intercropped with non- fruit tree species, Robusta CAS produced higher SOC (57.564 tC/ha) compared to the Arabica CAS (54.543 tC/ha). In contrast, Arabica CAS stored more SOC (54.01 tC/ha) compared to Robusta CAS (49.635 tC/Kg) when intercropped with fruit trees like Artocarpus heterophyllus Lam. and Mangifera indica L. Under the coffee monocrop systems, Robusta coffee sequestered 4.86 tC/ha more SOC than Arabica coffee. The study showed that a farmer growing Robusta coffee intercropped with non-fruit trees is likely to benefit more from soil carbon credits than a farmer growing Arabica coffee with the same trees. Farmers growing Arabica coffee would sequester more carbon if intercropped with fruit trees. There is need for policy incentives that encourage the planting and maintenance of shade trees in coffee plantations for the benefit of carbon sequestration. [ABSTRACT FROM AUTHOR]

Many studies have shown that elevated atmospheric CO2 concentrations result in increased plant carbon inputs to soil that can accelerate the decomposition of native soil organic matter, an effect known as priming. Consequently, it is important to understand and quantify the priming effect for future predictions of carbon-climate feedbacks. There are potential pitfalls, however, when representing this complex system with a simple, first-order model. Here, we show that a multi-pool soil carbon model can match the change in bulk turnover time calculated from overall respiration and carbon stocks (a one-pool approach) at elevated CO2, without a change in decomposition rate constants of individual pools (i.e., without priming). Therefore, the priming effect cannot be quantified using a one-pool model alone, and even a two-pool model may be inadequate, depending on the effect size as well as the distribution of soil organic carbon and turnover times. In addition to standard measurements of carbon stocks and CO2 fluxes, we argue that quantifying the fate of new plant inputs requires isotopic tracers and microbial measurements. Our results offer insights into modeling and interpreting priming from observations. [ABSTRACT FROM AUTHOR]

Straw incorporation (SI) is a common practice in China and has important implications for agricultural sustainability. This study aimed to quantitatively summarise the response of top soil (0-20 cm) carbon (C) to SI under different agricultural management regimes. Results indicated that compared with straw removal (SR), SI significantly increased soil C storage by 12 %. Moreover, incorporation of chopped straw with tillage treatment (ploughing and rotary tillage) increased C storage compared to unchopped straw without tillage treatment. SI implementation with upland cropping, in the northwest and northeast resulted in higher C storage compared with rice cropping, and in the northern and southern regions. Changes in soil C were observed based on SI variables, including tillage and straw amounts in fine-textured soils, however straw amount rather than tillage treatment exhibited a greater influence on soil C in coarse-textured soils. We concluded SI implementation with increased amounts of chopped straw for a longer duration was favourable to soil C sequestration in Chinese croplands. Furthermore, we estimated if SI was popularised across all of China's agricultural regions, soil C sequestration potential would reach 48.2 ~ 56.2 Tg C year. SI practices should therefore be encouraged. [ABSTRACT FROM AUTHOR]

Plant and soil carbon pools are two important elements of forest ecosystems and both are affected by many environmental factors. Although forest types are typically characterized using species composition, the ways in which soil carbon storage (C S ) is distributed between plants and soil in different forest types and the factors influencing this distribution remain unclear. In this study, we calculated C S in plants and soil by sampling 108 tree plots and 324 soil profiles to determine whether plant and soil C S varied significantly among different forest types in this region. Boosted regression tree analysis was used to detect factors influencing forest C S allocation. The results showed that plant C S varied from 68.09 t ha −1 in aspen-white birch forests (AW) to 117.81 t ha −1 in mixed Korean pine-broadleaved hardwood forests (KB). Conversely, soil C S varied from 153.23 t ha −1 in KB to 261.58 t ha −1 in AW. Forest management was the main factor influencing plant C S while soil C S was most influenced by factors relevant to moisture. The influence on the ratio of plant C S to soil C S was quite complex because the dynamics of the relationship were affected by managerial, climatic, and topographical factors. In addition to species composition, ecosystem C S also varied in different forest types and was influenced by complex factors related to climate, topography, and forest management. [ABSTRACT FROM AUTHOR]

Management of soil in agricultural ecosystem is considered to be important in maintaining soil health and soil carbon storage. Various combinations of inorganic fertilizers, FYM and crop residues were assessed in a wheat crop grown in alluvial soil for two consecutive years. We studied several attributes like soil organic carbon (SOC), soil total carbon (TC), soil carbon storage (SCS), soil moisture content (SMC), easily mineralizable N along with above ground and below ground biomass, photosynthetic rate and grain yields during various growth stages. Wheat biomass yield was increased with application of organic amendments, while carbon assimilation by plant photosynthesis during the reproductive stages enhanced with increment of SOC. We recorded about ∼10.88% and 10.52% organic SCS in soil depth of 0–15 cm and about ∼11.50% and 12.46% in soil depth of 15–30 cm under 100% NPK + CR + FYM and 80% NPK + CR + FYM treatments, respectively. Hence, CR and FYM in combination can maintain SOC stock considerably and 80% NPK + CR + FYM substitutes 20% inorganic fertilizer without compromising crop growth and development. [ABSTRACT FROM AUTHOR]

• Alpine steppe is sensitive to N but not P in Qilian mountain. • The species diversity was negatively correlated with N and NP, but not P. • P is ineffective on plant diversity under N enrichment. • MN may counteract the negative effects of N enrichment. Plant diversity strongly affected the grassland productivity and soil C and N storage. Nitrogen enrichment weakens the stability of the ecosystem through decreased biodiversity. Mowing is a viable management tool for the maintenance of diversity in grasslands. However, it is unclear how plant diversity affects soil C and N storage in mowing (or phosphorus) under N enrichment in the semi-arid alpine steppe. In the present study, a 3-year trial has investigated the effects of nitrogen, mowing (or phosphorus), and their interactions on plant diversity and soil C and N storage in a semi-arid alpine steppe in Qilian mountains, northern China. We found that aboveground biomass (AGB) was significantly increased in N (nitrogen added alone) and NP (both nitrogen and phosphorus added), significantly decreased in M (mowing) across the three years (2019–2021) (P < 0.05), and significantly increased by 21.4% in the third year in MN (nitrogen added at the time of mowing). Plant diversity was significantly decreased in N and NP, but had no significant effect under M, MN, and P across the three years. We found that SOC stock was significantly decreased by 13% in the 0–10 cm soil layer in N, while increased by 6% at the 10–20 cm soil layer in MN. In contrast, NP had no significant effect on SOC stock and TN stock, while both NO 3 –N and AP significantly increased. M increased the relative biomass of sedge and forb, while N increased the relative biomass of grass and decreased the relative biomass of forb. Forb is positively correlated with C storage and negatively correlated with N storage, while the grass is the opposite. Therefore, the results indicated that mowing modulated the effects of N addition on diversity loss and carbon stock loss. In contrast, phosphorus is ineffective for the negative effect of nitrogen on grassland species diversity. [ABSTRACT FROM AUTHOR]

Due to the importance of wetlands as a global carbon pool, explicit research on and management of the carbon storage of wetlands have drawn much attention. Within a single climatic zone, South Korea has various types of inland wetlands such as tidal salt marshes, freshwater lakes, rivers and peatlands, thereby providing an excellent platform for scientific investigation to identify patterns and key controlling factors of carbon budget in different inland wetlands. We estimated the amount of soil organic carbon (SOC) of 2444 inland wetlands in South Korea by cluster analysis and Monte-Carlo simulation using data from South Korea's National Wetland Inventory and their economic values by literature review. In addition, we identified key controlling factors that are closely related to SOC of 34 inland wetlands by correlation analysis and ANOVA test. We found that the total SOC stock of inland wetlands in South Korea is 16.3 ± 0.4 TgC (22.3 ± 0.6 kgC m−2), which is 5.3–5.5% of the total SOC stock of the country, and the annual carbon sequestration rate is 60.7 ± 9.8 gC m−2 yr−1. The economic value of the total SOC stock is 2.0 ± 0.1 billion USD (2.8 ± 0.1 USD m−2), and that of the annual sequestration rate is 5.5 ± 0.9 million USD yr−1 (7.5 ± 1.2 10−3 USD m−2 yr−1). The mean atmospheric temperature and soil characteristics including water content, total nitrogen and electrical conductivity showed positive correlations with SOC, suggesting the importance of hydrology and water chemistry as key determinants of SOC. In addition, inland wetlands with different dominant plant species showed significantly different SOC, probably because primary production and chemical composition of vegetation are strongly associated with carbon input into wetlands. However, annual precipitation and soil pH showed no correlation with SOC. Our results demonstrate that the carbon budget of inland wetlands in South Korea is considerable, and its economic value is closely related to characteristics of soil and vegetation. • The total SOC stock of inland wetlands in South Korea is 16.3 ± 0.4 TgC (2.0 ± 0.1 billion USD). • The annual carbon sequestration rate of inland wetlands in South Korea is 60.7 ± 9.8 gC m−2 yr−1 (7.5 ± 1.2 10−3 USD m−2 yr−1). • The key controlling factors of inland wetlands' SOC are MAT, soil WC, TN, EC, and dominant plant species. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) is a significant component of the global carbon (C) cycle. Changes in SOC storage affect atmospheric CO2 concentrations on decadal to centennial timescales. The C-TOOL model was developed to simulate farm- and regional-scale effects of management on medium- to long-term SOC storage in the profile of well-drained agricultural mineral soils. C-TOOL uses three SOC pools for both the topsoil (0–25 cm) and the subsoil (25–100 cm), and applies temperature-dependent first order kinetics to regulate C turnover. C-TOOL also enables the simulation of 14 C turnover. The simple model structure facilitates calibration and requires few inputs (mean monthly air temperature, soil clay content, soil C/N ratio and C in organic inputs). The model was parameterised using data from 19 treatments drawn from seven long-term field experiments in the United Kingdom, Sweden and Denmark. It was found that the initial SOC content had to be optimised for each experiment, but also that one set of values for other model parameters could be applied at all sites. With this set of parameters, C-TOOL can be applied more widely to evaluate effects of management options on SOC storage in temperate agricultural soils. C-TOOL simulates observed losses of SOC in soils under intensive agricultural use and the gain in SOC derived from large inputs of animal manure and inclusion of perennial grassland. The model simulates changes in SOC for the entire profile, but lack of data on subsoil SOC storage hampers a proper model evaluation. Experimental verification of management effects on subsoil C storage, subsoil C inputs from roots, and vertical transport of C in the soil profile remains prioritised research areas. [ABSTRACT FROM AUTHOR]

Abstract: Increasing atmospheric concentrations of greenhouse gases has caused grievous global warming and associated consequences. Lowering carbon footprint to promote the development of cleaner production demands the immediate attention. In this study, the carbon footprint calculations were performed on five cropping systems in North China Plain from 2003 to 2010. The five cropping systems included sweet potato → cotton → sweet potato → winter wheat–summer maize (SpCSpWS, 4-year cycle), ryegrass–cotton → peanut → winter wheat–summer maize (RCPWS, 3-year cycle), peanut → winter wheat–summer maize (PWS, 2-year cycle), winter wheat–summer maize (WS, 1-year cycle), and continuous cotton (Cont C), established in a randomized complete-block design with three replicates. We used a modified carbon footprint calculation with localized greenhouse gas emissions parameters to analyze the carbon footprint of each cropping system per unit area, per kg biomass, and per unit economic output. Results showed that the lowest annual carbon footprint values were observed in SpCSpWS among the five cropping systems, which were only 27.9%, 28.2% and 25.0% of those in WS rotation system (the highest carbon footprint) in terms of per unit area, per unit biomass, and per unit economic output, respectively. The five cropping systems showed the order of SpCSpWS < Cont C < RCPWS < PWS < WS sorting by their annual carbon footprint calculated by all the three metrics above-mentioned. Results revealed that appropriate diversified crop rotation systems could contribute to decreased carbon footprint compared with conventional intensive crop production system in North China Plain. [Copyright &y& Elsevier]

The semi-arid grasslands in Inner Mongolia, China have been degraded by long-term grazing. A series of ecological restoration strategies have been implemented to improve grassland service. However, little is known about the effect of these ecological restoration practices on soil carbon and nitrogen storage. In this study, characteristics of vegetation and soil properties under continued grazing and exclusion of livestock for six years due to a nationwide conservation program-'Returning Grazing Lands to Grasslands (RGLG)' were examined in semi-arid Hulun Buir grassland in Inner Mongolia, China. The results show that removal of grazing for six years resulted in a significant recovery in vegetation with higher above and below-ground biomass, but a lower soil bulk density and pH value. After six years of grazing exclusion, soil organic C and total N storage increased by 13.9% and 17.1%, respectively, which could be partly explained by decreased loss and increased input of C and N to soil. The effects of grazing exclusion on soil C and N concentration and storage primarily occurred in the upper soil depths. The results indicate that removal of grazing pressure within the RGLG program was an effective restoration approach to control grassland degradation in this region. However, more comprehensive studies are needed to evaluate the effectiveness of the RGLG program and to improve the management strategies for grassland restoration in this area. [ABSTRACT FROM AUTHOR]

Tree-based intercropping (TBI) systems, consisting of a medium to fast-growing woody species planted in widely-spaced rows with crops cultivated between tree rows, are a potential sink for atmospheric carbon dioxide (CO2). TBI systems contribute to farm income in the long-term by improving soil quality, as indicated by soil carbon (C) storage, generating profits from crop plus tree production and potentially through C credit trading. The objectives of the current study were: (1) to evaluate soil C and nitrogen (N) stocks in soil depth increments in the 0-30 cm layer between tree rows of nine-year old hybrid poplar-hay intercropping systems, to compare these to C and N stocks in adjacent agricultural systems; and (2) to determine how hay yield, litterfall and percent total light transmittance (PTLT) were related to soil C and N stocks between tree rows and in adjacent agricultural systems. The two TBI study sites (St. Edouard and St. Paulin) had a hay intercrop with alternating rows of hybrid poplar clones and hardwoods and included an adjacent agricultural system with no trees (i.e., the control plots). Soil C and N stocks were greater in the 0-5 cm depth increment of the TBI system within 1 m of the hardwood row, to the west of the poplar row, compared to the sampling point 1 m east of poplar at St. Edouard (p = 0.02). However, the agricultural system stored more soil C than the nine-year old TBI system in the 20-30 cm and 0-30 cm depth increments. Accumulation of soil C in the 20-30 cm depth increment could be due to tillage-induced burial of non-harvested crop residues at the bottom of the plow-pan. Soil C and N stocks were similar at all depth increments in TBI and agricultural systems at St. Paulin. Soil C and N stocks were not related to hay yield, litterfall and PTLT at St. Paulin, but hay yield and PTLT were significantly correlated (R = 0.87, p < 0.05, n = 21), with lower hay yield in proximity to trees in the TBI system and similar hay yields in the middle of alleys as in the agricultural system. Nine years of TBI practices did not produce significant gains in soil C and N stocks in the 0-30 cm layer, indicating that the total C budget, including C sequestered in trees and unharvested components (litterfall and roots), must be assessed to determine the long-term profitability of TBI systems in Canada. [ABSTRACT FROM AUTHOR]

Adopting field investigation and indoor analysis methods, the distribution patterns of soil active carbon and soil carbon storage in the soil profiles of Quercus aliena var. acuteserrata (Matoutan Forest, I), Pinus tabuliformis (II), Pinus armandii (III), pine-oak mixed forest (IV), Picea asperata (V), and Quercus aliena var. acuteserrata (Xinjiashan Forest, VI) of Qinling Mountains were studied in August 2013. The results showed that soil organic carbon (SOC), microbial biomass carbon (MBC), dissolved organic carbon (DOC), and easily oxidizable carbon (EOC) decreased with the increase of soil depth along the different forest soil profiles. The SOC and DOC contents of different depths along the soil profiles of P. asperata and pine-oak mixed forest were higher than in the other studied forest soils, and the order of the mean SOC and DOC along the different soil profiles was V>IV>I>II>III>VI. The contents of soil MBC of the different forest soil profiles were 71. 25-710. 05 mg.kg-1, with a content sequence of I>V>IV>III>II>VI. The content of EOC along the whole soil profile of pine-oak mixed forest had a largest decline, and the order of the mean EOC was IV>V>I>II>III>VI. The sequence of soil organic carbon storage of the 0-60 cm soil layer was V>I>IV>III>VI>II. The MBC, DOC and EOC contents of the different forest soils were significanty correlated to each other. There was significant positive correlation among soil active carbon and TOC, TN. Meanwhile, there was no significant correlation between soil active carbon and other soil basic physicochemical properties. [ABSTRACT FROM AUTHOR]

Understanding the impacts of eco-construction project on grassland soil carbon storage is crucial to assess the effectiveness of the project and its role in carbon cycling of the grassland ecosystems. Using IPCC carbon budget inventory method, this paper analyzed the influence of Beijing and Tianjin Sand Source Control Project (BTSSCP) on the grassland soil carbon storage between 2000 and 2006 in Xilingol League, Inner Mongolia, and evaluated the time needed to reach the maximal soil carbon density for three management practices (i. e. , sown pasture, aerial sowing pasture, and grazing exclosure). Results showed that the BTSSCP significantly increased soil carbon storage, with a carbon sequestration of 59. 26 × 104 t C from 2000 to 2006. The rate and effectiveness of soil carbon sequestration varied significantly with management practices, with the highest rate in sown pasture (0. 25 t C ∙ hm-2 ∙ a-1) while a greater benefit of soil carbon sequestration in the grazing exclosure (63 million yuan). Compared with other grassland vegetations, lowland meadow and temperate meadow steppe both had higher carbon sequestration rates of 0.14 t C ∙ hm-2 ∙ a-1. Long time would be needed to reach the maximum soil carbon density in grassland under the three practices, yet shorter for sown pasture with average of 57. 75 years. [ABSTRACT FROM AUTHOR]

Exotic earthworm introductions can alter above- and belowground properties of temperate forests, but the net impacts on forest soil carbon (C) dynamics are poorly understood. We used a mesocosm experiment to examine the impacts of earthworm species belonging to three different ecological groups (Lumbricus terrestris [anecic], Aporrectodea trapezoides [endogeic], and Eisenia fetida [epigeic]) on C distributions and storage in reconstructed soil profiles from a sandy temperate forest soil by measuring C02 and dissolved organic carbon (DOC) losses, litter C incorporation into soil, and soil C storage with monospecific and species combinations as treatments. Soil C02 loss was 30% greater from the Endogeic X Epigeic treatment than from controls (no earthworms) over the first 45 days; C02 losses from monospecific treatments did not differ from controls. DOC losses were three orders of magnitude lower than C02 losses, and were similar across earthworm community treatments. Communities with the anecic species accelerated litter C mass loss by 31-39% with differential mass loss of litter types (Acer rubrum > Populus grandidentata > Fagus grandifolia > Quercus rubra > Pinus strobus) indicative of leaf litter preference. Burrow system volume, continuity, and size distribution differed across earthworm treatments but did not affect cumulative C02 or DOC losses. However, burrow system structure controlled vertical C redistribution by mediating the contributions of leaf litter to A-horizon C and ? pools, as indicated by strong correlations between (1) subsurface vertical burrows made by anecic species, and accelerated leaf litter mass losses (with the exception of P. strobus); and (2) dense burrow networks in the A-horizon and the C and ? properties of these pools. Final soil C storage was slightly lower in earthworm treatments, indicating that increased leaf litter C inputs into soil were more than offset by losses as C02 and DOC across earthworm community treatments. [ABSTRACT FROM AUTHOR]

Abstract: Land-use change resulting from natural restoration probably enhances the carbon sequestration capacity of terrestrial ecosystems. To explore those factors which foster changes in the soil carbon pool in forest restoration, a study comparing soil organic carbon at different vegetation succession stages along a 150-year chronosequence was conducted in the Ziwuling forest region located in the central part of the Loess Plateau, China. It showed that in long-term (~150yr) secondary forest succession the soil organic carbon storage (Cs), soil organic carbon (SOC), total nitrogen (TN), and C/N ratio all increased rapidly and tended to be at their highest at roughly the 50-year restoration mark. From this point onward the values gradually stabilized indicating that the SOC and the TN accumulated mainly in the early restoration stages. The Cs was significantly and positively correlated with the SOC, the TN, and the C/N ratio (P <0.01). The Cs in the soil was higher in the upper rather than the lower soil layers. However, the increments of the Cs mainly changed in the lower soil layers. Soil water storage was not the key factor influencing the Cs. The results suggested that changes to the Cs were the result of the accumulation of the SOC and the TN during forest succession and this capacity has shown to be positively related to forest succession on the Loess Plateau, China. [Copyright &y& Elsevier]

Abstract: Whether farmland serves as a carbon (C) source or sink depends on the balance of soil organic carbon (SOC) sequestration and greenhouse gas (GHG) emissions. Tillage practices critically affect the SOC concentration, SOC sequestration rate and soil carbon storage (SCS). The objective of this paper is to assess the tillage effects on SOC sequestration, SCS and C footprint. Tillage experiments were established on a double cropping system of winter wheat (Triticum aestivum L.) and summer corn (Zea mays L.) in the North China Plain since 2001 with three treatments: no tillage (NT), rotary tillage (RT) and conventional tillage (CT). In order to assess SOC sequestration efficiency under different tillage systems, SCS, SOC sequestration rate, hidden carbon cost (HCC), indexes of sustainability (I s ) and C productivity (CP) were computed in this study. Results showed that the SCS increased with years of residue retention. The SCS attained the highest degree in 2007, which was about 25%–30% higher than that in 2004. The net SOC sequestration rate was the highest in NT and lowest in CT, while HCC was lowest under NT and highest under CT. The value of I s for CT, RT and NT treatments was 1.46, 1.79 and 1.88, respectively, and that of CP was 11.02, 12.79 and 10.57, respectively. Therefore, it can be concluded that NT provides a good option for increasing SOC sequestration for agriculture in the North China Plain. [Copyright &y& Elsevier]

Abstract: Rehabilitation of degraded lands needs appropriate mix of land use and erosion control measures, and is often associated with carbon (C) sequestration in the soil profile. However, topographic attributes play a deterministic role in the rate of C accretion in degraded sloping lands. This study was carried out to assess the effect of slope aspect on soil C sequestration, soil aggregation and soil moisture retention in aggradation phase of a denuded land in eastern India. Eight treatments of horti-silvi-pastural system integrated with in-situ moisture conservation were taken in randomized block design during 2000 to 2006. Indigofera teysmanni was taken as the silviculture component and hedgerows of the species were used uniformly for all the treatments. A significant interaction effect of the rehabilitation system and slope aspect was observed for residual soil moisture content, soil organic C (SOC) content, SOC stock, size distribution of aggregates and C content in aggregate fractions. Treatments with trenches of 0.45×0.45×1.0m dimension at 0.5mu/s of fruit plants conserved significantly higher soil moisture even at 87mm of evaporativity. On an average, the north facing (NF) aspect had 1.13 and 0.75g 100g−1 higher soil moisture than the east facing (EF) aspect in the 0–15cm and 15–30cm soil depths, respectively. The SOC concentration was higher by 11–12% in the NF than the EF aspect. In the 0–30cm soil profile, the SOC stock varied from 31.55 to 37.91Mgha−1 in the EF aspect and from 35.01 to 41.28Mgha−1 in the NF aspect, as compared to the initial stock of 18.19 and 19.06Mgha−1 in the two aspects, respectively. The NF aspect had 0.35 to 3.17Mgha−1 higher SOC stock in the 0–15cm soil, 0.64 to 3.03Mgha−1 in the 15–30cm soil and 1.85 to 4.59Mgha−1 in the whole 0–30cm soil profile. Averaged over all the rehabilitation systems, the NF aspect accumulated extra C to the tune of 0.19, 0.18 and 0.36Mgha−1 yr−1 than the EF aspect in the 0–15, 15–30 and 0–30cm soil layers, respectively. Under all the systems and slope aspects, small macroaggregates (>250μm) constituted the highest proportion, with values varying from 50.4–65.4% in the EF to 61.7–71.7% in the NF aspect. The C content in small macroaggregates was also higher than that in microaggregates and silt+clay size fractions. The study indicates slope aspect to be a significant factor in soil C sequestration, which also affects the aggregation pattern of soils under recovery. [Copyright &y& Elsevier]

Abstract: Dolomite formation in soils constitute a particular challenge because of: 1) scant magnesium content in continental environments as opposed to the marine medium, 2) the kinetic problem related to the incorporation of magnesium into the carbonate, and 3) the unknown role of soil dolomites in the global carbon cycle. Pedogenic dolomite formed at deeper soil levels (subsoil) before the development of petrocalcic horizon barriers was investigated in a semiarid region of SE Spain (Guadix–Baza basin). Mineralogical characterization, textural relationships and isotopic data concerning soil dolomite, together with the results of a precipitation experiment, provided fuller knowledge of the processes and conditions governing neoformation of dolomite in these soils. In the study case, dolomite enrichment occurs beyond the limit of major biological activity, which coincides with the rooting depth of native perennial plants in the semiarid soils studied. Textural studies reveal the corrosion of inherited dolomite crystals in the upper soil horizons and the formation of dolomite in depth in relation to a clayey material, composed mainly of smectites. Stable isotope distribution in dolomites throughout the profiles indicates a fractionation with depth. This is explained by the formation of dolomites after the dissolution of the pedogenic calcite. The calcite detected in the subsoil is interpreted here as a precursor of the neoformed dolomites that transport the isotopic signal associated with biological activity of soils to deeper layers. Dolomite formation appears to be favoured by the presence of clay minerals in the precipitation media. Clays retain water during evapotranspiration stages, which drastically change the transport properties of the media and promote the incorporation of Mg into the structure of the neoformed Ca,Mg-carbonate. As confirmed by laboratory experiments, diffusion-controlled crystal-growth processes lead to the formation a precursory “protodolomite” with disordered Ca,Mg distribution from a fluid locally supersaturated in dolomite. [Copyright &y& Elsevier]

Respiration by plants and microorganisms is primarily responsible for mediating carbon exchanges between the biosphere and atmosphere. Climate warming has the potential to influence the activity of these organisms, regulating exchanges between carbon pools. Physiological 'down-regulation' of warm-adapted species (acclimation) could ameliorate the predicted respiratory losses of soil carbon under climate change scenarios, but unlike plants and symbiotic microbes, the existence of this phenomenon in heterotrophic soil microbes remains controversial. Previous studies using complex soil microbial communities are unable to distinguish physiological acclimation from other community-scale adjustments. We explored the temperature-sensitivity of individual saprotrophic basidiomycete fungi growing in agar, showing definitively that these widespread heterotrophic fungi can acclimate to temperature. In almost all cases, the warm-acclimated individuals had lower growth and respiration rates at intermediate temperatures than cold-acclimated isolates. Inclusion of such microbial physiological responses to warming is essential to enhance the robustness of global climate-ecosystem carbon models. [ABSTRACT FROM AUTHOR]

Warming is known to reduce soil carbon (C) stocks by promoting microbial respiration, which is associated with the decomposition of microbial residue carbon (MRC). However, the relative contribution of MRC to soil organic carbon (SOC) across temperature gradients is poorly understood. Here, we investigated the contribution of MRC to SOC along two independent elevation gradients of our model system (i.e., the Tibetan Plateau and Shennongjia Mountain in China). Our results showed that local temperature increases were negatively correlated with MRC and SOC. Further analyses revealed that rising temperature reduced SOC via decreasing MRC, which helps to explain future reductions in SOC under climate warming. Our findings demonstrate that climate warming has the potential to reduce C sequestration by increasing the decomposition of MRC, exacerbating the positive feedback between rising temperature and CO 2 efflux. Our study also considered the influence of multiple environmental factors such as soil pH and moisture, which were more important in controlling SOC than microbial traits such as microbial life-style strategies and metabolic efficiency. Together, our work suggests an important mechanism underlying long-term soil C sequestration, which has important implications for the microbial-mediated C process in the face of global climate change., (© 2022 John Wiley & Sons Ltd.)