Sequestration Response Research Articles

Soil water content and RubisCO activity control the carbon storage in soil under different land uses in Sanjiang Plain, China

Soil carbon storage plays a crucial role in mitigating the climate warming and is significantly impacted by the land use pattern. To better understand soil carbon stability and the underlying microbial mechanism, based on qPCR, ELISA, and fluorescence techniques, the effects of land use changes on soil microbial abundance, enzyme activity, and soil carbon storage were investigated in the complex ecosystems of cropland, forestland, and wetland along three typical river (Wolvlan river, Bielahong river, Wusuli river) basin in Sanjiang Plain, China. We hypothesised that croplands soil carbon storage is lower than forestlands and wetlands, which is regulated by soil water content, microbe and enzyme activity. Results showed that topsoil TC in wetlands (85.54 mg·g−1) was higher than those in croplands (33.46 mg·g−1) and forestlands (46.13 mg·g−1). Topsoil water content increased 73.90 % and 71.64 % in wetlands than in farmland and forestlands, respectively. Additionally, reclamation diminished topsoil carbon storage. In croplands, soil dissolved organic carbon, microbial biomass carbon, microbial biomass nitrogen, available nitrogen, bacterial abundance, and soil enzymes (i.e., RubisCO, β-glucosidase, cellobiohydrolase, 1,4-N-acetylglucosaminidase and acid phosphatase) activities were substantially lower than those in wetlands. Structural equation modeling showed that soil carbon storage was positively related to soil water content and RubisCO activity but negatively related to soil bacterial abundance. Soil water content had the largest standardised total positive effect coefficient and indirectly influenced soil carbon storage by affecting RubisCO activity. Soil depth had a greater effect on SMC, hydrolase and site had a greater effect on bacteria and fungi abundance. The results highlight that the alteration of carbon fixing enzyme activity by soil water content is a crucial mechanism for soil carbon sequestration in response to land-use change. Management strategies that conserve natural wetlands, increase soil water content and minimize land disturbance would be effective in maintaining soil carbon stocks.

Repeatable self-healing with carbon sequestration function using ammonium bicarbonate

Repeatable self-healing at the same cracking site is one of the essential issues in self-healing concrete. The inorganic admixture ammonium bicarbonate (NH4HCO3) was proposed as the primary healing agent in this study to achieve repeatable self-healing. Among ammonium carbamate (NH2COONH4), NH4HCO3, ammonium acetate (CH3COONH4) and calcium hydroxide (Ca(OH)2), the molar ratio of precipitation reaction and the effect of calcium extraction were determined. Whether before or after the self-healing, ammonia water (NH3·H2O) invariably exists in the products and will be carbonised to regenerate NH4HCO3, which was verified by Fourier transform infrared (FT-IR). The proposed self-healing solution achieves a two-in-one strategy for calcium extraction and carbon sequestration in response to the global strategy for carbon neutrality. Self-healing experiments have been performed. The results suggested that the healing efficiency of the crack area of the tri-component (NH2COONH4, NH4HCO3 and CH3COONH4) is up to five times higher than that of the control group. Three cycles of self-healing in the simulated system and actual crack environment concluded that the regeneration potential of NH4HCO3 could be enhanced after the completion of more cyclic self-healing processes due to the increasing amount of NH3·H2O at the same cracking site.

Diversified responses of vegetation carbon uptake to urbanization: a national-scale analysis

IntroductionUrbanization converts vegetated lands into impervious surfaces and often degrades vegetation carbon sequestration in urban ecosystems. At the same time, the impact on urban vegetation growth from urban expansion could be spatially diverse given different natural environments and urban management practices.MethodsHere we applied time-series remotely sensed images and analyzed the urban growth for all the prefecture-level cities across China during 2001–2019, and compared the impact of urbanization on vegetation carbon uptake proxied by MODIS (MOD17A2H) net primary productivity (NPP) on Google Earth Engine platform.ResultsThe result indicated that at the national scale, the carbon uptake flux in urban areas was only 19% compared to that in the nonurban vegetated counterparts. The total urban area expanded by 22% and the vegetation carbon uptake in the newly urbanized zones was averagely reduced by 16% during the period, but with high spatio-temporal heterogeneity among cities and with exceptions demonstrating even improved NPP, highlighting diversified responses of vegetation carbon sequestration to urban sprawl. The changes of vegetation carbon sequestration in response to urbanization were found to be spatially clustered.DiscussionWe conclude that urban land management strategies unique to cities may attribute to the diversified responses of vegetation carbon capture to urbanization.

Plant invasion mediates the regulation of topsoil organic carbon sequestration by the fungal community in coastal wetlands

Spartina alterniflora, which is native to the Atlantic coast, has extensively invaded mangroves/marshes and hence seriously altered coastal soil organic carbon (SOC) sequestration along the Pacific coast. Fungi are directly engaged in the SOC cycle, but how the fungal community impacts coastal carbon sequestration in response to S. alterniflora invasion remains unclear. We explored the fungal community shifts in relation to SOC changes by comparing 6 pairs of independent sites (i.e., dominant native plants vs. S. alterniflora) along a 2,500 km coastal transect in southeastern China. Our results showed that the invasion reduced the fungal diversity and shifted the assemblage processes of the abundant subcommunity, not the rare subcommunity, from determinism (0.409) to stochasticity (0.556). The invasion decreased network topological properties (e.g., network size, centrality, natural connectivity, etc.), cohesion, robustness, and the relative abundance of keystone taxa but increased the vulnerability of the fungal community. Importantly, the Shannon index, total cohesion and keystone taxa of the fungal community were significantly positively correlated with SOC concentration, SOC storage and recalcitrant organic carbon (ROC) but not with labile organic carbon (LOC). The structural equation model further showed that the fungal community diversity, complexity and keystone taxa directly regulated SOC storage under S. alterniflora invasion. Overall, we provide new insights into fungal community shifts and cooccurrence patterns under S. alterniflora invasion, helping us better understand the impact of invasion on SOC cycling and its microbial mechanisms, which will benefit future restoration and optimal coastal management.

Plant species diversity enhances soil gross nitrogen transformations in a subtropical forest, southwest China

Abstract Plant species diversity (PSD) regulates ecosystem structure and functions, and is a key issue we need to consider when design vegetation restoration projects. Increasing PSD has been shown to promote or decrease soil nitrogen (N) availability, but the underlying mechanisms have not been well explored. Here, 45 plots with the Shannon–Weiner indices ranging from 0.15 to 3.57 were selected in a subtropical forest to explore the effect of PSD on soil N transformations. Higher PSD significantly enhanced the rates of gross N mineralization, gross nitrification, microbial N immobilization, net N mineralization, net nitrification and the contents of soil total N and inorganic N. Structural equation modelling showed that PSD indirectly impacted gross N transformations via its roles in regulating soil organic matter, mineral and microbial traits. Higher PSD stimulated gross N mineralization and nitrification mainly via its positive effects on microbial biomass content and gene abundances of chiA, archaeal or bacterial amoA, while increased microbial N immobilization mainly due to its stimulation of soil organic matter. Synthesis and applications. Our findings highlight the crucial role of PSD in stimulating soil N availability and provide a mechanistic understanding which can be integrated into Earth system models to better predict soil N availability and C sequestration in response to PSD.

Tradeoffs of fungal and bacterial residues mediate soil carbon dynamics under persistent drought in subtropical evergreen forests

Global climate change has greatly accelerated hydrological processes, causing significant increases in frequency and intensity of drought events, which may have a great impact on soil carbon (C) dynamics. Microbial residues are frequently represented as the important constituents involved in soil C formation and stability. However, how persistent drought influences microbial residues to regulate soil C cycling remains elusive, especially in forest ecosystems. In this study, we investigated drought effects on microbial (fungal and bacterial) residues and soil C dynamics by a 7-year filed experiment (2013−2020) with a 70 % rainfall reduction in a subtropical evergreen forest of Eastern China. Soil samples (0–10 cm) were collected in 2014, 2015, 2016, and 2020 with drought duration of 1, 2, 3, and 7 years, and soil moisture, soil temperature, soil organic carbon (SOC) and soil nitrogen (N) were measured. The contents of microbial (fungal and bacterial) residues were quantified by amino sugar biomarkers. Our results showed that fungal residues significantly decreased with increasing drought duration, which were mainly induced by the decline of soil N and soil moisture, causing a decrease in soil C under the 7-year persistent drought. In contrast, bacterial residues increased with drought duration due to fast adaption of bacteria to drought and aggregate protection. The retention of bacterial residues might be preserved as a “nutrient reservoir” to cope with the long-term drought in the near future. These results suggest that persistent drought-induced tradeoffs between fungal and bacterial residues mediate soil C dynamics. Fungal residues were the essential prerequisite for soil C sequestration in response to drought, while bacterial residues may mainly regulate soil C cycling under the prolonged drought. Therefore, microbial residues are imperative to understand the responses of microbial-derived C to drought, which could be integrated into terrestrial C models to accurately predict soil C dynamics in unpredictable climate regimes in forest ecosystems.

The interconnected dynamics of ribonucleoprotein condensates and the endoplasmic reticulum

A hallmark of eukaryotic cells is the ability to compartmentalize essential reactions into membrane‐bound and membrane‐less organelles. Membrane‐bound organelles work together through transport vesicles and membrane‐to‐membrane organelle contact sites to traffic cargo and distribute lipids throughout the cell. Conversely, many membrane‐less organelles are condensates of messenger RNAs and proteins (RNPs), which participate throughout the mRNA life cycle. Our recent work uncovered that these two classes of organelles – membranous and membrane‐less – join forces to potentially shunt mRNAs between the endoplasmic reticulum and RNP condensates involved in mRNA silencing, degradation and sequestration in response to stress. We use two model RNP condensates, processing (P)‐bodies and stress granules, to dissect the relationships between the endoplasmic reticulum and RNP condensate biogenesis, composition, and disassembly.

Jet stream position explains regional anomalies in European beech forest productivity and tree growth

The mechanistic pathways connecting ocean-atmosphere variability and terrestrial productivity are well-established theoretically, but remain challenging to quantify empirically. Such quantification will greatly improve the assessment and prediction of changes in terrestrial carbon sequestration in response to dynamically induced climatic extremes. The jet stream latitude (JSL) over the North Atlantic-European domain provides a synthetic and robust physical framework that integrates climate variability not accounted for by atmospheric circulation patterns alone. Surface climate impacts of north-south summer JSL displacements are not uniform across Europe, but rather create a northwestern-southeastern dipole in forest productivity and radial-growth anomalies. Summer JSL variability over the eastern North Atlantic-European domain (5-40E) exerts the strongest impact on European beech, inducing anomalies of up to 30% in modelled gross primary productivity and 50% in radial tree growth. The net effects of JSL movements on terrestrial carbon fluxes depend on forest density, carbon stocks, and productivity imbalances across biogeographic regions.

Interleukin-6 triggers toxic neuronal iron sequestration in response to pathological α-synuclein.

SUMMARYα-synuclein (α-syn) aggregation and accumulation drive neurodegeneration in Parkinson’s disease (PD). The substantia nigra of patients with PD contains excess iron, yet the underlying mechanism accounting for this iron accumulation is unclear. Here, we show that misfolded α-syn activates microglia, which release interleukin 6 (IL-6). IL-6, via its trans-signaling pathway, induces changes in the neuronal iron transcriptome that promote ferrous iron uptake and decrease cellular iron export via a pathway we term the cellular iron sequestration response, or CISR. The brains of patients with PD exhibit molecular signatures of the IL-6-mediated CISR. Genetic deletion of IL-6, or treatment with the iron chelator deferiprone, reduces pathological α-syn toxicity in a mouse model of sporadic PD. These data suggest that IL-6-induced CISR leads to toxic neuronal iron accumulation, contributing to synuclein-induced neurodegeneration.

Grassland management strategies influence soil C, N, and P sequestration through shifting plant community composition in a semi-arid grasslands of northern China

Current studies regarding the effects of grassland management strategies on the soil nutrient cycle have mostly focused on soil organic carbon (SOC). Less is known about the responses of SOC, total nitrogen (TN), and total phosphorous (TP) stocks to grassland management strategies at different soil depths. We therefore quantified vertical variations in SOC, TN, and TP stocks as well as controlling factors under three grassland management strategies (i.e., enclosure control, grazing twice a year, grazing combined with mowing) in 2014 and 2017 in a semi-arid grassland of northern China. We found that grazing twice a year and grazing combined with mowing led to an increase in plant production as well as soil C and N sequestration during 2014 to 2017. Changes in plant aboveground biomass (AGB), belowground biomass (BGB), and root-to-shoot ratio (R:S) all exerted significant positive effects on changes in soil C and N sequestration in the surface soil layer (0–30 cm), while changes in AGB and plant community composition played a more important role in mediating soil C, N, and P sequestration in response to grassland management strategies in the subsoil layer (30–100 cm). Specifically, grassland management strategies influence soil C, N, and P sequestration capacity by altering plant community composition. The results of this study provide new insights into the response mechanisms of plants and soils to grassland management practices and offer a range of new possible strategies that might be applied to the effective management of semi-arid grasslands.

Organic phosphorus cycling may control grassland responses to nitrogen deposition: a long-term field manipulation and modelling study

Abstract. Ecosystems limited in phosphorous (P) are widespread, yet there is limited understanding of how these ecosystems may respond to anthropogenic deposition of nitrogen (N) and the interconnected effects on the biogeochemical cycling of carbon (C), N, and P. Here, we investigate the consequences of enhanced N addition for the C–N–P pools of two P-limited grasslands, one acidic and one limestone, occurring on contrasting soils, and we explore their responses to a long-term nutrient-manipulation experiment. We do this by combining data with an integrated C–N–P cycling model (N14CP). We explore the role of P-access mechanisms by allowing these to vary in the modelling framework and comparing model plant–soil C–N–P outputs to empirical data. Combinations of organic P access and inorganic P availability most closely representing empirical data were used to simulate the grasslands and quantify their temporal response to nutrient manipulation. The model suggested that access to organic P is a key determinant of grassland nutrient limitation and responses to experimental N and P manipulation. A high rate of organic P access allowed the acidic grassland to overcome N-induced P limitation, increasing biomass C input to soil and promoting soil organic carbon (SOC) sequestration in response to N addition. Conversely, poor accessibility of organic P for the limestone grassland meant N provision exacerbated P limitation and reduced biomass input to the soil, reducing soil carbon storage. Plant acquisition of organic P may therefore play an important role in reducing P limitation and determining responses to anthropogenic changes in nutrient availability. We conclude that grasslands differing in their access to organic P may respond to N deposition in contrasting ways, and where access is limited, soil organic carbon stocks could decline.

K63-linked ubiquitylation induces global sequestration of mitochondria

Even though K63-linked polyubiquitin chains do not target proteins for proteasomal degradation, they play nevertheless a complementary protective role in maintaining protein homeostasis by directing malfunctioning proteins and organelles to inclusion bodies or autophagosomes. A paradigm for this process is the sequestration and autophagic degradation of dysfunctional mitochondria. Although studies have shown that K63-ubiquitylation of mitochondrial proteins by the ubiquitin ligase Parkin is important in this process, it is presently not clear if this modification also suffices to initiate this cascade of events. To address this question, we have engineered the ubiquitin ligase ProxE3, which in an inducible manner synthesizes K63-linked ubiquitin chains on the surface of mitochondria. We found that the presence of K63-linked ubiquitin chains on mitochondria resulted in the recruitment of the ubiquitin adaptor p62 and induced a dramatic redistribution of mitochondria, which was reminiscent to the Parkin-facilitated sequestration in response to mitochondrial uncoupler. However, ProxE3 did not induce autophagic degradation of mitochondria. Our data show that K63-linked ubiquitin chains at the mitochondrial membrane are sufficient for the induction of mitochondrial sequestration, but not mitophagy, without the need of extrinsically inflicting mitochondrial dysfunction.

Iron Regulation in Elderly Asian Elephants (Elephas maximus) Chronically Infected With Mycobacterium tuberculosis.

Restriction of nutrients to pathogens (nutritional immunity) is a critical innate immune response mechanism that operates when pathogens such as Mycobacterium tuberculosis have the potential to evade humoral immunity. Tuberculosis is of growing concern for zoological collections worldwide and is well-illustrated by infections of Asian and African elephants, where tuberculosis is difficult to diagnose. Here, we investigated hematological parameters and iron deposition in liver, lung, and spleen of three Asian elephants (Elephas maximus) infected with Mycobacterium tuberculosis. For reference purposes, we analyzed tissue samples from control M. tuberculosis-negative elephants with and without evidence of inflammation and/or chronic disease. Molecular analyses of bacterial lesions of post mortally collected tissues confirmed M. tuberculosis infection in three elephants. DNA sequencing of the bacterial cultures demonstrated a single source of infection, most likely of human origin. In these elephants, we observed moderate microcytic anemia as well as liver (mild), lung (moderate) and spleen (severe) iron accumulation, the latter mainly occurring in macrophages. Macrophage iron sequestration in response to infection and inflammation is caused by inhibition of iron export via hepcidin-dependent and independent mechanisms. The hepatic mRNA levels of the iron-regulating hormone hepcidin were increased in only one control elephant suffering from chronic inflammation without mycobacterial infection. By contrast, all three tuberculosis-infected elephants showed low hepcidin mRNA levels in the liver and low serum hepcidin concentrations. In addition, hepatic ferroportin mRNA expression was high. This suggests that the hepcidin/ferroportin regulatory system aims to counteract iron restriction in splenic macrophages in M. tuberculosis infected elephants to provide iron for erythropoiesis and to limit iron availability for a pathogen that predominantly proliferates in macrophages. Tuberculosis infections appear to have lingered for more than 30 years in the three infected elephants, and decreased iron availability for mycobacterial proliferation may have forced the bacteria into a persistent, non-proliferative state. As a result, therapeutic iron substitution may not have been beneficial in these elephants, as this therapy may have enhanced progression of the infection.

Effects of land use and land cover change on carbon sequestration and adaptive management in Shanghai, China

Achieving well-being for all, while mitigating climate change, is a central idea in the UN Sustainable Development Goals (SDGs) and one of the most pressing global challenges. Land use and land cover change are affecting the global and regional climate change through the carbon emissions. Meanwhile, carbon sequestration could replenish and contribute to the decrease of CO2 emissions. Rapid urbanized areas have typical urbanized characteristics and carbon reduction target. Therefore, it is a vital issue to explore the carbon sequestration in rapid urbanized area. This paper analyzed the mechanism between carbon sequestration and land use and land cover change in Shanghai city. Based on the Landsat TM/ETM images from 1990 to 2015 and using the InVEST model, we assessed the temporal and spatial variations of carbon sequestration in response to the expansion of built-up areas and obtained a reliable estimate of terrestrial carbon sequestration at 30 m × 30 m grid scale, including biomass and soil carbon stocks. The results show that the total carbon stock decreased by 73.19 × 105 t during the period 1990–2015, representing 0.48% per year. The urbanization process in response to land use and land cover change has significant negative impacts on carbon sequestration capacity in the urban ecosystem. According to these results, some potential policy measures are proposed for mitigating terrestrial carbon losses for Shanghai, which are mainly manifested in adaptive management for carbon sequestration, contributing to achieve SGDs and sustainable development.

Warming and elevated CO2 interactively affect the photosynthetic carbon of maize plant retained in major farming soils

ABSTRACT Warming and elevated CO2 (eCO2) may influence the input of photosynthetic carbon (C) into soils and subsequent soil C storage. The biochemical properties vary among soils, which likely act different roles in the fate of photosynthetic C and soil C sequestration in response to warming and eCO2. However, the interactive effects of climate change and soil types on the photosynthetic C retained in soil and relevant mechanisms are poorly understood. We performed a pot experiment in open-top chambers to examine the effects of eCO2 (550 ppm) combined with elevated temperature (eT, 2 °C higher than the air temperature) on the retention of plant-C of maize (Zea mays L.) grown in Phaeozem, Fluvisol, Kastanozem and Acrisol with 13CO2 labeling at the silking stage. The proportion of 13C to the total fixed 13C increased by 44.6%, 96.1% and 41.9% in Phaeozem under eT, eCO2 and eT plus eCO2 treatments compared with control, while decreased in other three soils in response to either eCO2, eT or eT plus eCO2. The effect of climate change on fresh C input in maize cropping soils depended on soil type, and soil net C losses may occur in the Fluvisol, Kastanozem and Acrisol under climate change. Abbreviations: eCO2: elevated CO2, 550ppm; eT: warming; aCO2: ambient CO2, 400ppm; aT: ambient temperature; OTC: open-top chamber; DOC: dissolved organic carbon; SOC: soil organic carbon; C: carbon; S: soil; T: temperature.

Is There a Role for Glutaredoxins and BOLAs in the Perception of the Cellular Iron Status in Plants?

Glutaredoxins (GRXs) have at least three major identified functions. In apoforms, they exhibit oxidoreductase activity controlling notably protein glutathionylation/deglutathionylation. In holoforms, i.e., iron–sulfur (Fe–S) cluster-bridging forms, they act as maturation factors for the biogenesis of Fe–S proteins or as regulators of iron homeostasis contributing directly or indirectly to the sensing of cellular iron status and/or distribution. The latter functions seem intimately connected with the capacity of specific GRXs to form [2Fe–2S] cluster-bridging homodimeric or heterodimeric complexes with BOLA proteins. In yeast species, both proteins modulate the localization and/or activity of transcription factors regulating genes coding for proteins involved in iron uptake and intracellular sequestration in response notably to iron deficiency. Whereas vertebrate GRX and BOLA isoforms may display similar functions, the involved partner proteins are different. We perform here a critical evaluation of the results supporting the implication of both protein families in similar signaling pathways in plants and provide ideas and experimental strategies to delineate further their functions.

Soil Carbon Sequestration in Long-Term Fertilization Under Jute-Rice-Wheat Agro-Ecosystem

ABSTRACTSoil organic carbon (SOC) sequestration in response to long-term fertilizer management practices under jute-rice-wheat agro-ecosystem in alluvial soils was studied using a modeling approach. Fertilizer management practices included nitrogen (N), phosphorus (P) and potassium (K) fertilization, manure application, and root-stubble retention of all three crops. Soil carbon (C) model RothC was used to simulate the critical C input rates needed to maintain initial soil C level in long timescale (44 years). SOC change was significantly influenced by the long-term fertilizer management practices and the edaphic variable of initial SOC content. The effects of fertilizer combination “100%NPK+FYM” on SOC changes were most significant over “100%NPK” fertilization. If the 100% NPK fertilizer along with manure applied with stubble and roots retention of all crops, alluvial soils of such agro-ecosystem would act as a net C sink, and the average SOC density kept increasing from 18.18 Mg ha−1 during 1972 to the current average of ∼22 Mg ha−1 during 2065 s. On an average, the critical C input was estimated to be 5.30 Mg C ha−1 yr−1, depending on local soil and climatic conditions. The critical C input could be effectively estimated using a summary model driven by current SOC level, mean annual temperature, precipitation, and soil clay content. Such information will provide a baseline for assessing soil C dynamics under potential changes in fertilizer and crop residues management practices, and thus enable development of management strategies for effectively mitigating climate change through soil C sequestration.

Influencia de la fertilización mineral sobre la retención de carbono en una plantación de pino

Con el objetivo de estimar el efecto que ejerce la fertilización mineral sobre la retención de carbono aplicada de forma fraccionada en los primeros cinco años de establecida la plantación el trabajo consistió en la evaluación de 288 árboles de diferentes edades durante los primeros 41 años de edad en una plantación de Pinus caribaea, establecida en la Estación Experimental Forestal de Viñales en Pinar del Río, Cuba. A partir de un diseño de bloques al azar, se establecieron siete tratamientos diferenciados por las dosis de NPK y regímenes de aplicación, más un tratamiento testigo sin la aplicación de fertilizante químico. Se realizaron mediciones de altura y diámetro y se calculó el volumen a diferentes edades. El análisis evidenció que las dosis de 600 g árbol-1, 800 g árbol-1 y 1 000 g árbol-1 favorecen la retención de carbono de P. caribaea. Con la aplicación de una dosis única de 300 g árbol-1 se obtienen valores inferiores a los del tratamiento testigo.

Modulation of Litter Decomposition by the Soil Microbial Food Web Under Influence of Land Use Change.

Soil microbial communities modulate soil organic matter (SOM) dynamics by catalyzing litter decomposition. However, our understanding of how litter-derived carbon (C) flows through the microbial portion of the soil food web is far from comprehensive. This information is necessary to facilitate reliable predictions of soil C cycling and sequestration in response to a changing environment such as land use change in the form of agricultural abandonment. To examine the flow of litter-derived C through the soil microbial food web and it’s response to land use change, we carried out an incubation experiment with soils from six fields; three recently abandoned and three long term abandoned fields. In these soils, the fate of 13C-labeled plant litter was followed by analyzing phospholipid fatty acids (PLFA) over a period of 56 days. The litter-amended soils were sampled over time to measure 13CO2 and mineral N dynamics. Microbial 13C-incorporation patterns revealed a clear succession of microbial groups during litter decomposition. Fungi were first to incorporate 13C-label, followed by G− bacteria, G+ bacteria, actinomycetes and micro-fauna. The order in which various microbial groups responded to litter decomposition was similar across all the fields examined, with no clear distinction between recent and long-term abandoned soils. Although the microbial biomass was initially higher in long-term abandoned soils, the net amount of 13C-labeled litter that was incorporated by the soil microbial community was ultimately comparable between recent and long-term abandoned fields. In relative terms, this means there was a higher efficiency of litter-derived 13C-incorporation in recent abandoned soil microbial communities compared to long-term abandoned soils, most likely due to a net shift from SOM-derived C toward root-derived C input in the soil microbial food web following land-abandonment.

Shifts in soil organic carbon dynamics under detritus input manipulations in a coniferous forest ecosystem in subtropical China

The underlying mechanism of how shifts in plant detritus input impact soil organic carbon (SOC) dynamics is not fully understood. Here we investigated the soil C content in different fractions (aggregates, labile and recalcitrant pool) after two years of detritus input manipulations (i.e. detritus input and removal treatment–DIRT: control, CK; double litter, DL; no litter, NL; no roots, NR; no aboveground litter and no roots, NRNL) in a coniferous forest (Platycladus orientalis (Linn.) Franco) ecosystem in subtropical China. The root exclusion treatments (NR and NRNL) significantly decreased the macro-aggregate (>2000 μm) fraction by 23.4%–27.7% compared to CK after two-year detritus input manipulation, and accordingly decreased the C content in macroaggregates. In contrast, the aboveground litter removal and addition (DL and NL) did not significantly impact those properties. Labile SOC significantly declined in the detritus removal treatments, while recalcitrant SOC remained relatively stable. In addition, root exclusion significantly reduced total microbial biomass and most of the taxonomic biomarkers compared to the CK. Fungal biomass were positively correlated with the proportion of macroaggregates across treatments. Principal component analysis revealed the separation of root exclusion treatments from the other detritus input manipulations was based on lower soil C content and proportion of macroaggregates. Overall, our results suggest that future shifts in plant detritus input, especially decreases in belowground litter inputs, can strongly and rapidly reduce SOC pools by reducing the proportion of macroaggregates and the C content in macroaggregates, highlighting the importance of root in regulating soil C sequestration in response to future climatic scenarios.