MCTR1 enhances the resolution of lipopolysaccharide‐induced lung injury through STAT6‐mediated resident M2 alveolar macrophage polarization in mice

Acute respiratory distress syndrome (ARDS) is a fatal disease characterized by excessive infiltration of inflammatory cells. MCTR1 is an endogenously pro‐resolution lipid mediator. We tested the hypothesis that MCTR1 accelerates inflammation resolution through resident M2 alveolar macrophage polarization. The mice received MCTR1 via intraperitoneal administration 3 days after LPS stimulation, and then, the bronchoalveolar lavage (BAL) fluid was collected 24 hours later to measure the neutrophil numbers. Flow cytometry was used to sort the resident and recruited macrophages. Post‐treatment with MCTR1 offered dramatic benefits in the resolution phase of LPS‐induced lung injury, including decreased neutrophil numbers, reduced BAL fluid protein and albumin concentrations and reduced histological injury. In addition, the expression of the M2 markers Arg1, FIZZ1, Remlα, CD206 and Dectin‐1 was increased on resident macrophages in the LPS + MCTR1 group. Resident macrophage depletion abrogated the therapeutic effects of MCTR1, and reinjection of the sorted resident macrophages into the lung decreased neutrophil numbers. Finally, treatment with MCTR1 increased STAT6 phosphorylation. The STAT6 inhibitor AS1517499 abolished the beneficial effects of MCTR1. In conclusion, MCTR1 promotes resident M2 alveolar macrophage polarization via the STAT6 pathway to accelerate resolution of LPS‐induced lung injury.     

Real-time measurement of particulate matter deposition in the lung

Abstract

Air pollution and cigarette smoke are recognized health risks. A method was developed for the measurement of the deposition fraction (DF) of polydisperse particulate matter (PM) in human airways. Ten normal volunteers [three females, age range 18–67 years, mean age (SD) 43.9 (14)] made single breath exhalations after inhalation to total lung capacity. The exhaled breath was diverted to a multichannel laser diffraction chamber where the particulate profiler measured 0.3–1.0-µm particles. DF was inversely related to expiration flow-rate, 0.69 (0.02) at 4 l min^?1 and 0.5 (0.01) at 13 l min^?1, respectively (p<0.05), and was influenced by the inhalation flow-rate [0.70 (0.02) at 3 l min^?1 and 0.59 (0.02) at 13 l min^?1, respectively (p<0.05)], while no differences were found between nasal and oral inhalation (0.68 (0.05) versus 0.67 (0.06), p>0.05). Higher breath holding times were associated with elevated DF [0.74 (0.02) at 20 s, and 0.62 (0.05) without breath holding (p<0.01)]. When the expiratory flow was controlled and the breath hold time standardized, DF was reproducible (CV?=?4.85%). PM can be measured in the exhaled breath and its DF can be quantified using a portable device. These methods may be useful in studies investigating the health effects of air pollution and tobacco smoke.     

城市森林调控空气颗粒物功能研究进展

受城市扩张、工业发展、汽车保有量增加的影响,空气颗粒物目前已成为诸多城市空气的首要污染物。而城市森林作为城市生态建设中最大的唯一具有自净功能的生态系统,不仅为城市高污染环境下的居民提供了相对洁净的休闲游憩空间,还对净化空气颗粒物起重要作用。从城市森林调控空气颗粒物的机理、分析方法、植物个体、群落及不同类型城市森林调控空气颗粒物的功能差异及其时空变化规律等方面进行阐述。结果表明:目前有关物理降尘的研究较多,涉及化学除尘的研究尚缺;应用重量法测定植物滞尘量的研究较多,质量浓度法测定城市森林净化空气颗粒物功能的研究较少。在未来一段时间,森林植被化学除尘的过程与机理,城市森林调控空气颗粒物的多方面、系统性研究及相关研究成果的转化与实际应用将会是重要的研究方向。     

Placental mitochondrial methylation and exposure to airborne particulate matter in the early life environment: An ENVIRONAGE birth cohort study

Most research to date has focused on epigenetic modifications in the nuclear genome, with little attention devoted to mitochondrial DNA (mtDNA). Placental mtDNA content has been shown to respond to environmental exposures that induce oxidative stress, including airborne particulate matter (PM). Damaged or non-functioning mitochondria are specifically degraded through mitophagy, exemplified by lower mtDNA content, and could be primed by epigenetic modifications in the mtDNA. We studied placental mtDNA methylation in the context of the early life exposome. We investigated placental tissue from 381 mother-newborn pairs that were enrolled in the ENVIRONAGE birth cohort. We determined mtDNA methylation by bisulfite-pyrosequencing in 2 regions, i.e., the D-loop control region and 12S rRNA (MT-RNR1), and measured mtDNA content by qPCR. PM_2.5 exposure was calculated for each participant''s home address using a dispersion model. An interquartile range (IQR) increment in PM_2.5 exposure over the entire pregnancy was positively associated with mtDNA methylation (MT-RNR1: +0.91%, P = 0.01 and D-loop: +0.21%, P = 0.05) and inversely associated with mtDNA content (relative change of −15.60%, P = 0.001) in placental tissue. mtDNA methylation was estimated to mediate 54% [P = 0.01 (MT-RNR1)] and 27% [P = 0.06 (D-loop)] of the inverse association between PM_2.5 exposure and mtDNA content. This study provides new insight into the mechanisms of altered mitochondrial function in the early life environment. Epigenetic modifications in the mitochondrial genome, especially in the MT-RNR1 region, substantially mediate the association between PM_2.5 exposure during gestation and placental mtDNA content, which could reflect signs of mitophagy and mitochondrial death.     

The application of sterol biomarkers to the study of the sources of particulate organic matter in the Solo River system and and Serayu River,Java, Indonesia

Sterols were analyzed in suspended particles collected in January 1991 in the Solo River system and in the Serayu River, Java, Indonesia. Free sterols were extracted from particles larger than 0.7 μm and analyzed, after derivatization into their trimethylsilyl esters, by GC and GC/MS. Concentrations of total sterols ranged from 438 to 7922 ng/1, or from 2.4 to 183.8 ng/mg of total suspended matter, which varied from 3.3 to 400 and 471 mg/l, respectively in the Serayu River and at the downstream station in the Solo River. POC concentrations also varied in a wide range, from 0.91 to 4.72 and 6.13% of TSM, respectively at the above stations, and were associated with sterol/POC values ranging from 0.15 to 1.75 μg/mg. Eleven structures of C₂₇, C₂₈ and C₂₉ sterols and associated stanols were identified. 28Δ^3,22 was only found at downstream stations in the Solo River and in the Serayu River. This unique distribution, different from that of other C₂₇, C₂₈ and C₂₉ sterols, suggests a predominantly autochthonous origin for these compounds associated with an increased planktonic biosynthesis near the estuary. Concentrations of 28Δ⁵, 29Δ^5,22 and 29Δ⁵ showed similar spatial distributions and increased downstream, reflecting the significant accumulation of organic matter originating from the vegetation of the various drainage basins. Values of the autochthonous versus terrigenous sterol index, defined as 27Δ⁵/29Δ^5,22 + 29Δ⁵ were in the 1.4–1.9 range at upstream stations, whereas at downstream stations lower values were found, 0.4–0.6, which also corresponded to higher concentrations of TSM and lower POC values. Insofar as the stanol/stenol values can be used to estimate the bacterial activity of oxic waters, simultaneous variations of C₂₇, and C₂₉ stenol/stanol pairs suggest rather different bacterial degradation capacities of autochthonous versus allochthonous organic matter. The wide differencies between the values of the stenol/stanol pairs observed in one of the main tributaries and in downstream stations of the Solo River is evidence that allochthonous organic matter is much more resistant than autochthonous matter. The low index value observed in the Serayu River indicates the highly refractory nature of both autochthonous and allochthonous organic material.     

Long non‐coding RNA expressed in macrophage co‐varies with the inflammatory phenotype during macrophage development and polarization

Advances in microarray, RNA‐seq and omics techniques, thousands of long non‐coding RNAs (lncRNAs) with unknown functions have been discovered. LncRNAs have presented a diverse perspective on gene regulation in diverse biological processes, especially in human immune response. Macrophages participate in the whole phase of immune inflammatory response. They are able to shape their phenotype and arouse extensive functional activation after receiving physiological and pathological stimuli. Emerging studies indicated that lncRNAs participated in the gene regulatory network during complex biological processes of macrophage, including macrophage‐induced inflammatory responses. Here, we reviewed the existing knowledges of lncRNAs in the processes of macrophage development and polarization, and their roles in several different inflammatory diseases. Specifically, we focused on how lncRNAs function in macrophage, which might help to discover some potential therapeutic targets and diagnostic biomarkers.     

Conceptualizing soil organic matter into particulate and mineral‐associated forms to address global change in the 21st century

Managing soil organic matter (SOM) stocks to address global change challenges requires well‐substantiated knowledge of SOM behavior that can be clearly communicated between scientists, management practitioners, and policy makers. However, SOM is incredibly complex and requires separation into multiple components with contrasting behavior in order to study and predict its dynamics. Numerous diverse SOM separation schemes are currently used, making cross‐study comparisons difficult and hindering broad‐scale generalizations. Here, we recommend separating SOM into particulate (POM) and mineral‐associated (MAOM) forms, two SOM components that are fundamentally different in terms of their formation, persistence, and functioning. We provide evidence of their highly contrasting physical and chemical properties, mean residence times in soil, and responses to land use change, plant litter inputs, warming, CO₂ enrichment, and N fertilization. Conceptualizing SOM into POM versus MAOM is a feasible, well‐supported, and useful framework that will allow scientists to move beyond studies of bulk SOM, but also use a consistent separation scheme across studies. Ultimately, we propose the POM versus MAOM framework as the best way forward to understand and predict broad‐scale SOM dynamics in the context of global change challenges and provide necessary recommendations to managers and policy makers.     

Impaired cardiac mitochondrial function and contractile reserve following an acute exposure to environmental particulate matter

Background

It has been suggested that mitochondrial function plays a central role in cardiovascular diseases associated with particulate matter inhalation. The aim of this study was to evaluate this hypothesis, with focus on cardiac O₂ and energetic metabolism, and its impact over cardiac contractility.

Methods

Swiss mice were intranasally instilled with either residual oil fly ash (ROFA) (1.0 mg/kg body weight) or saline solution. After 1, 3 or 5 h of exposure, O₂ consumption was evaluated in heart tissue samples. Mitochondrial respiration, respiratory chain complexes activity, membrane potential and ATP content and production rate were assessed in isolated mitochondria. Cardiac contractile reserve was evaluated according to the Langendorff technique.

Results

Three hours after ROFA exposure, tissue O₂ consumption was significantly decreased by 35% (from 1180 ± 70 to 760 ± 60 ng-at O/min g tissue), as well as mitochondrial rest (state 4) and active (state 3) respiration, by 30 and 24%, respectively (control state 4: 88 ± 5 ng-at O/min mg protein; state 3: 240 ± 20 ng-at O/min mg protein). These findings were associated with decreased complex II activity, mitochondrial depolarization and deficient ATP production. Even though basal contractility was not modified (control: 75 ± 5 mm Hg), isolated perfused hearts failed to properly respond to isoproterenol in ROFA-exposed mice. Tissue O₂ consumption rates positively correlated with cardiac contractile state in controls (r² = 0.8271), but not in treated mice (r² = 0.1396).

General Significance

The present results show an impaired mitochondrial function associated with deficient cardiac contractility, which could represent an early cardiovascular alteration after the exposure to environmental particulate matter.     

施用生物炭对华北平原农田土壤容重、阳离子交换量和颗粒有机质含量的影响

以华北平原高产农田3年定位试验为基础,研究了生物炭与矿质肥配施对土壤容重、阳离子交换量和颗粒有机质组分中碳、氮含量的影响.试验共设4个处理：单施氮磷钾肥（CK）;氮磷钾肥+2250 kg·hm^-2生物炭（C₁）;氮磷钾肥+4500 kg·hm^-2生物炭（C₂）;炭基缓释肥（750 kg·hm^-2,CN）.结果表明： 与CK相比,C₁和C₂处理显著降低了0～7.5 cm土层容重,降低幅度分别为4.5%和6.0%;施用生物炭增加了0～15 cm土层的阳离子交换量,其中C₂处理增加了24.5%;在0～7.5 cm土层,C₁处理土壤颗粒有机质组分中的碳、氮浓度较CK处理分别增加了250%和85%,C₂处理分别增加了260%和120%.施用生物炭3年后土壤理化特性得到明显改善,并在碳增汇和温室减排方面具有潜在积极效应.     

Long-term effects of elevated atmospheric CO2 on below-ground biomass and transformations to soil organic matter in grassland

We determined the effects of elevated [CO₂] on the quantity and quality of below-ground biomass and several soil organic matter pools at the conclusion of an eight-year CO₂ enrichment experiment on native tallgrass prairie. Plots in open-top chambers were exposed continuously to ambient and twice-ambient [CO₂] from early April through late October of each year. Soil was sampled to a depth of 30 cm beneath and next to the crowns of C4 grasses in these plots and in unchambered plots. Elevated [CO₂] increased the standing crops of rhizomes (87%), coarse roots (46%), and fibrous roots (40%) but had no effect on root litter (mostly fine root fragments and sloughed cortex material >500 μm). Soil C and N stocks also increased under elevated [CO₂], with accumulations in the silt/clay fraction over twice that of particulate organic matter (POM; >53 μm). The mostly root-like, light POM (density ≤1.8 Mg m^-3) appeared to turn over more rapidly, while the more amorphous and rendered heavy POM (density >1.8 Mg m^-3) accumulated under elevated [CO₂]. Overall, rhizome and root C:N ratios were not greatly affected by CO₂ enrichment. However, elevated [CO₂] increased the C:N ratios of root litter and POM in the surface 5 cm and induced a small but significant increase in the C:N ratio of the silt/clay fraction to a depth of 15 cm. Our data suggest that 8 years of CO₂ enrichment may have affected elements of the N cycle (including mineralization, immobilization, and asymbiotic fixation) but that any changes in N dynamics were insufficient to prevent significant plant growth responses. This revised version was published online in June 2006 with corrections to the Cover Date.     

萘对川西亚高山森林土壤呼吸、可溶性有机质和微生物生物量的影响

通过原位控制试验,研究了萘对川西亚高山森林土壤动物抑制效率、土壤呼吸、可溶性有机质和微生物生物量的影响.结果表明:萘施用显著抑制了大型和中小型土壤节肢动物的个体密度和类群数量,个体密度分别下降76.3%~78.5%和83.3%~84.8%,类群数量分别降低48.3%~56.1%和45.8%~58.3%.萘处理与对照的土壤呼吸速率季节动态呈单峰曲线,分别以2月和8月为最低值和最高值,而且未受萘施用的显著影响.与对照相比,萘处理显著降低了8月和10月土壤可溶性碳和可溶性氮含量,以及4月和8月微生物生物量碳,增加了4月的微生物生物量碳氮比.萘处理和采样时间的交互作用显著影响了微生物生物量碳和微生物生物量氮,但对土壤动物个体密度和类群数量以及可溶性碳含量影响不显著.总体上,萘作为抑制剂,在川西亚高山森林土壤能够有效地抑制土壤动物节肢动物,且并未显著影响土壤呼吸,但对土壤碳氮组分造成了不同程度的影响.     

A new approach to estimate the in situ fractional degradation rate of organic matter and nitrogen in wheat yeast concentrates

In the classic in situ method, small particles are removed during rinsing and hence their fractional degradation rate cannot be determined. A new approach was developed to estimate the fractional degradation rate of nutrients in small particles. This approach was based on an alternative rinsing method to reduce the particulate matter loss during rinsing and on quantifying the particulate matter loss that occurs during incubation in the rumen itself. To quantify particulate matter loss during incubation, loss of small particles during the in situ incubation was studied using undegradable silica with different particle sizes. Particulate matter loss during incubation was limited to particles smaller than ~40 μm with a mean fractional particulate matter loss rate of 0.035 h⁻¹ (first experiment) and 0.073 h⁻¹ (second experiment) and an undegradable fraction of 0.001 and 0.050, respectively. In the second experiment, the fractional particulate matter loss rate after rinsing in a water bath at 50 strokes per minute (s.p.m.) (0.215 h⁻¹) and the undegradable fraction at 20 s.p.m. (0.461) were significantly larger than that upon incubation in the rumen, whereas the fractional particulate matter loss rate (0.140 and 0.087 h⁻¹, respectively) and the undegradable fraction (0.330 and 0.075, respectively) after rinsing at 30 and 40 s.p.m. did not differ with that upon rumen incubation. This new approach was applied to estimate the in situ fractional degradation rate of insoluble organic matter (OM) and insoluble nitrogen (N) in three different wheat yeast concentrates (WYC). These WYC were characterised by a high fraction of small particles and estimating their fractional degradation rate was not possible using the traditional washing machine rinsing method. The new rinsing method increased the mean non-washout fraction of OM and N in these products from 0.113 and 0.084 (washing machine method) to 0.670 and 0.782, respectively. The mean effective degradation (ED) without correction for particulate matter loss of OM and of N was 0.714 and 0.601, respectively, and significant differences were observed between the WYC products. Applying the correction for particulate matter loss reduced the mean ED of OM to 0.676 (30 s.p.m.) and 0.477 (40 s.p.m.), and reduced the mean ED of N to 0.475 (30 s.p.m.) and 0.328 (40 s.p.m.). These marked reductions in fractional degradation rate upon correction for small particulate matter loss emphasised the pronounced effect of correction for undegraded particulate matter loss on the fractional disappearance rates of OM and N in WYC products.     

Tidal variation in bacteria,phytoplankton, zooplankton,mysids, fish and suspended particulate matter in the turbidity zone of the Elbe estuary; Interrelationships and causes

In June 1992, an extensive investigation programme was carried out in the turbidity zone of the Elbe river. Special attention was paid to salinity and suspended particulate matter (SPM) and their influence on bacteria, phytoplankton, zooplankton, mysids and fish. SPM was separated into three fractions of different settling velocities. Mean settling velocity (w_s) was 0.05 cm s⁻¹. The major part of SPM belonged to the slow settling fraction (w_s<0.02 cm s⁻¹). Bacterial exoenzymatic activity showed a positive correlation with SPM and chlorophyll-a content, and also to total dissolved free amino acids. Phytoplankton biomass reached maximum values of 5.7 μg chlorophyll-a l⁻¹ at ebb tide. Chlorophyll-a correlated negatively with salinity, indicating riverine input of phytoplankton. A positive correlation was found between chlorophyll-a and dissolved oxygen. Abundance of zooplankton species and their developmental stages varied over the tidal cycles; abundance of cirriped larvae and copepodite stages of the dominant speciesEurytemora affinis (Copepoda, Crustacea) was positively correlated with salinity. Individual filtering rates (IFR) ofEurytemora affinis were negatively affected by the SPM content of the water. Maximum IFR for adults was 7.2 ml h⁻¹. Community grazing reached maximum rates of 30.3 ml l⁻¹ h⁻¹ (i.e. 72.7% d⁻¹). The dominant mysidNeomysis integer showed maximum abundance at night, possibly resulting from diel vertical migration. Abundance ofN. integer was positively correlated with SPM content. The fish community, consisting of 17 fish species, was characterised by high densities of smelt (Osmerus eperlanus). A positive correlation was found between salinity and abundance of typical marine fish species, such as sprat (Sprattus sprattus). Similar temporal variation of abundance of smelt, sprat, andEurytemora copepodites indicates processes of habitat preference of these planktivorous fish in relation to optimal food supply. SPM was the factor controlling both distribution of organisms and the turnover of nutrients. Salinity only was important for the distribution of organisms.     

Soil organic matter,nutrient distribution,fungal and microbial biomass and enzyme activities in a forest beech stand on the Apennines of southern Italy

The aim of this study was to analyse the amount and qualitative characteristics of organic matter (OM) in the litter horizon (considering leaf litter at different decomposition stages) and underlying soil to a 30-cm depth in a beech stand on the Apennines in southern Italy. Distribution of major nutrients as well as fungal and microbial biomass were also evaluated, in addition to beech leaf nutrient content monitor from full expansion to abscission in order to estimate annual nutrient input to soil from litterfall and nutrient retranslocation before abscission. OM was significantly higher in leaf litter. C/N ratio and the Na, Mn, Fe levels also decreased along the decomposition continuum, whereas N and S contents slowly decreased with soil depth. Generally, leaf nutrient content was also significantly lower in dead leaves, indicating efficient retranslocation to persistent organs. Fungal biomass was the highest in leaf layers, with no significant changes between spring and autumn samplings. Enzyme activities did not differ significantly along the decomposition continuum but marked decreases were found in the upper soil layer; these remained relatively constant, with the exception of laccase, at deeper soil depths. No seasonal effect on enzyme activities and OM content was found.     

Comparative study of the formation of oxidative damage marker 8-hydroxy-2'-deoxyguanosine (8-OHdG) adduct from the nucleoside 2'-deoxyguanosine by transition metals and suspensions of particulate matter in relation to metal content and redox reactivity

An association between exposure to ambient particulate matter (PM) and increased incidence of mortality and morbidity due to lung cancer and cardiovascular diseases has been demonstrated by recent epidemiological studies. Reactive oxygen species (ROS), especially hydroxyl radicals, generated by PM, have been suggested by many studies as an important factor in the oxidative damage of DNA by PM. The purpose of this study was to characterize quantitatively hydroxyl radical generation by various transition metals in the presence of H₂O₂ in aqueous buffer solution (pH 7.4) and hydroxylation of 2'-deoxyguanosine (dG) to 8-hydroxy-2'-deoxyguanosine (8-OHdG) under similar conditions. The order of metals' redox reactivity and hydroxyl radical production was Fe(II), V(IV), Cu(I), Cr(III), Ni(II), Co(II), Pb(II), Cd(II). Then, we investigated the generation of hydroxyl radicals in the presence of H₂O₂ by various airborne PM samples, such as total suspended particulate (TSP), PM₁₀, PM_2.5 (PM with aerodynamic diameter 10 and 2.5 μm), diesel exhaust particles (DEP), gasoline exhaust particles (GEP) and woodsmoke soot under the same conditions. When suspensions of PMs were incubated with H₂O₂ and dG at pH 7.4, all particles induced hydroxylation of dG and formation of 8-OHdG in a dose-dependent increase. Our findings demonstrated that PM's hydroxyl radical (HO√) generating ability and subsequent dG hydroxylation is associated with the concentration of water-soluble metals, especially Fe and V and other redox or ionizable transition metals and not their total metal content, or insoluble metal oxides, via a Fenton-driven reaction of H₂O₂ with metals. Additionally, we observed, by Electron paramagnetic resonance (EPR), that PM suspensions in the presence of H₂O₂ generated radical species with dG, which were spin-trapped by 2-methyl-2-nitroso-propane (MNP).     

Bacterial abundance and production in river sediments as related to the biochemical composition of particulate organic matter (POM)

The major proportion of heterotrophic activity in running waters islocalized on the solid surfaces of sediments in the benthic and hyporheic zoneand is dominated by microorganisms. However, this assertion is based on thestudies of small streams, and little is known about the microbial metabolism oforganic matter in river ecosystems. We therefore explored the relationshipsbetween bacterial abundance and production and the gradients of organic matterquality and quantity in sediments of a sixth-order lowland river (Spree,Germany). We found vertical gradients of detrital variables (particulateorganicmatter (POM), particulate organic carbon (POC), nitrogen (PN), and protein) andof bacterial variables (abundance, production, turnover time, and proportion ofbacterial carbon in total POC) in two different sediment types. These gradientswere steeper in stratified sediments than in the shifting sediments. Detritalvariables correlated strongly with bacterial abundance and production. The bestcorrelation was found for detrital variables indicating substrate quantity andquality (r_S = 0.90 for PN with abundance). Although bacterialbiomasscomprised only 0.7% of the POC (1.9% of PN, 3.4% of the protein) in sediments,the turnover of sedimentary organic carbon was fast (median = 62d), especially in the shifting sediments. Our findings demonstratethat sediment dynamics significantly foster organic carbon metabolism in riversystems. Thus, these sediments, which are typical for lowland rivers, stronglyinfluence the metabolism of the whole ecosystem.     

Carbon sequestration potential in perennial bioenergy crops: the importance of organic matter inputs and its physical protection

To date, only few studies have compared the soil organic carbon (SOC) sequestration potential between perennial woody and herbaceous crops. The main objective of this study was to assess the effect of perennial woody (poplar, black locust, willow) and herbaceous (giant reed, miscanthus, switchgrass) crops on SOC stock and its stabilization level after 6 years from plantation on an arable field. Seven SOC fractions related to different soil stabilization mechanisms were isolated by a combination of physical and chemical fractionation methods: unprotected (cPOM and fPOM), physically protected (iPOM), physically and chemically protected (HC‐μs + c), chemically protected (HC‐ds + c), and biochemically protected (NHC‐ds + c and NHC‐μs + c). The continuous C input to the soil and the minimal soil disturbance increased SOC stocks in the top 10 cm of soil, but not in deeper soil layers (10–30; 30–60; and 60–100 cm). In the top soil layer, greater SOC accumulation rates were observed under woody species (105 g m^?2 yr^‐1) than under herbaceous ones (71 g m^?2 yr^‐1) presumably due to a higher C input from leaf‐litter. The conversion from an arable maize monoculture to perennial bioenergy crops increased the organic C associated to the most labile organic matter (POM) fractions, which accounted for 38% of the total SOC stock across bioenergy crops, while no significant increments were observed in more recalcitrant (silt‐ and clay‐sized) fractions, highlighting that the POM fractions were the most prone to land‐use change. The iPOM fraction increased under all perennial bioenergy species compared to the arable field. In addition, the iPOM was higher under woody crops than under herbaceous ones because of the additional C inputs from leaf‐litter that occurred in the former. Conversion from arable cropping systems to perennial bioenergy crops can effectively increase the SOC stock and enlarge the SOC fraction that is physically protected within soil microaggregates.