In floodplain wetlands, alterations in hydrological patterns resulting from climate change and human activities could potentially diminish the carbon sequestration capacity of the soils, thereby having a negative impact onglobal climate change. However, the magnitude of the influence of hydrological regime change on soil carbon remains inadequately monitored. To address this research gap, we collected 306 upper layer (0–20cm) soil samples from the Dongting Lake floodplain between 2013 and 2022. The random forest (RF) algorithm was used to analyze the spatial distribution of soil organic carbon (SOC) in the upper soil layer of Dongting Lake floodplain and the impact of climate and hydrological changes in the past decade on surface SOC in the East Dongting Lake area was studied. In 2022, the SOC concentration of the Dongting Lake floodplain upper layer soil ranged from 3.34 to 17.67g kg^–1, averaging 10.43g kg^–1, with a corresponding SOC density of (2.65±0.49)kg m^–2and total SOC stock of 6.82Tg C (2.87–13.48Tg C). From 2013 to 2022, the SOC concentration of the upper soil layer of the East Dongting Lake area decreased from 18.37 to 10.82g kg^–1. This reduction could be attributed to climate and hydrological changes which reduce SOC input by reducing vegetation growth and accelerating SOC decomposition. Above 21.4m elevation, the amount of SOC loss increased with elevation, the loss being related to the decline in Miscanthuscommunity biomass and greater susceptibility of higher altitude areas to climate and hydrological changes. Our results highlight the need for strengthening wetland SOC management to increase SOC in the soils to helpcombat climate change.

Insight into the carbon turnover in soil aggregates and density fractions is essential for reducing the uncertainty in estimating carbon pools on the Tibetan Plateau, and how they vary with land use type is unclear. In this study, the effect of land use type on carbon storage and fractionation was quantified based on organic carbon and its ¹³C abundance at the microscale of soil aggregates and density fractions in Tibetan alpine ecosystems. The sequence of soil aggregate destruction in the land use types of plantation (13.1%)<shrubland (32.7%)<grassland (47.9%)<farmland (61.8%) shows that plantations strengthen the soil structure. Plantation land had a greater contribution of light fraction organic carbon (28.3%) but a lower contribution of mineral-associated organic carbon (40.6%) to the carbon stock compared to farmland (13.5 and 70.3%). Interestingly, plantation land enhanced the aggregational differentiation of organic carbon and ¹³C in each density fraction, whereas no such phenomenon existed in the soil organic carbon. Carbon isotope analyses revealed that carbon transfer in the plantation land occurred from the light fraction in macroaggregates (–24.9‰) to the mineral-associated fraction in microaggregates (–19.9‰). When compared to the other three land use types, the low transferability of carbon in aggregates and density fractions in plantation land provides a stable carbon pool for the Tibetan Plateau. This study shows that plantations can mitigate global climate change by slowing carbon transfer and increasing carbon storage at the microscale of aggregates and density fractions in alpine regions.

A comprehensive assessment of grain supply, demand, and ecosystem service flows is essential for identifying grain movement pathways, ensuring regional grain security, and guiding sustainable management strategies. However, current studies primarily focus on short-term grain provision services while neglecting the spatiotemporal variations in grain flows across different scales. This gap limits the identification of dynamic matching relationships and the formulation of optimization strategies for balancing grain flows. This study examined the spatiotemporal evolution of grain supply and demand in the Beijing-Tianjin-Hebei (BTH) region from 1980 to 2020. Using the Enhanced Two-Step Floating Catchment Area method, the grain provision ecosystem service flows were quantified, the changes in supply–demand matching under different grain flow scenarios were analyzed and the optimal distance threshold for grain flows was investigated. The results revealed that grain production follows a spatial distribution pattern characterized by high levels in the southeast and low levels in the northwest. A significant mismatch exists between supply and demand, and it shows a scale effect. Deficit areas are mainly concentrated in the northwest, while surplus areas are mainly located in the central and southern regions. As the spatial scale increases, the ecosystem service supply–demand ratio (SDR) classification becomes more clustered, while it exhibits greater spatial SDR heterogeneity at smaller scales. This study examined two distinct scenarios of grain provision ecosystem service flow dynamics based on 100 and 200 km distance thresholds. The flow increased significantly, from 2.17 to 11.81 million tons in the first scenario and from 2.41 to 12.37 million tons in the second scenario over nearly 40 years, forming a spatial movement pattern from the central and southern regions to the surrounding areas. Large flows were mainly concentrated in the interior of urban centers, with significant outflows between cities such as Baoding, Shijiazhuang, Xingtai, and Hengshui. At the county scale, supply–demand matching patterns remained consistent between the grain flows in the two scenarios. Notably, incorporating grain flow dynamics significantly reduced the number of grain-deficit areas compared to scenarios without grain flow. In 2020, grain-deficit counties decreased by 28.79 and 37.88%, and cities by 12.50 and 25.0% under the two scenarios, respectively. Furthermore, the distance threshold for achieving optimal supply and demand matching at the county scale was longer than at the city scale in both grain flow scenarios. This study provides valuable insights into the dynamic relationships and heterogeneous patterns of grain matching, and expands the research perspective on grain and ecosystem service flows across various spatiotemporal scales.

The lateral transport of labile organic carbon represents a critical pathway for soil organic carbon (SOC) loss, reducing organic carbon sequestration and increasing the risk of waterbody pollution. Livestock manureapplication on croplands serves as a common fertilizer reduction practice to sustain crop yields, enhance SOC sequestration, and reduce water erosion. However, limited quantitative assessments have examined the effects of livestock manure substitution on labile organic carbon lateral loss and fluxes in long-term experiments. This study conducted a three-year field investigation on subtropical sloping croplands to assess the impact of livestock manure substitution on dissolved organic carbon (DOC) and particulate organic carbon (POC) loss viasurface runoff, interflow and eroded sediments. There are four treatments: no fertilization (CK); chemical nitrogen fertilizer (SF),40% nitrogensubstitution with pig manure (PMF), and 100% nitrogensubstitution from pig manure (PM). Compared to SF treatment, long-term livestock manure substitution in PMF and PM treatments significantly (P<0.05) reduced annual cumulative surface runofffluxes by 13.5 and 21.6%, respectively. Manure applications decreased annual sediment fluxes by 12.9 and 19.1%, respectively. Soil water stable aggregates for mean weight diameter (MWD) increased significantly by 37.7 and 73.6%. Annual cumulative POC lossflux viaeroded sediment under PMF and PM treatments increased significantly (P<0.05) by 61.1 and 47.9%, respectively. The labile organic carbon loss fluxes, including DOC and POC losses, under PMF and PM treatmentsincreased significantly (P<0.05) by 11.9 and 31.4%, respectively. These results demonstrate that while water erosion intensity decreases due to enhanced soil aggregate stability, the risk of labile organic carbon loss increases after long-term livestock manure substitution in subtropical sloping croplands. Future research should examine labile organic carbon lateral migration under various soil types and slope gradients for livestock manure application in subtropical agricultural ecosystem croplands to better understand extreme rainfalleffects.

To examine the impact of anthropogenic land reconstruction, particularly the consolidation of small terraces into larger fields, on soil organic carbon (SOC), total nitrogen (TN) dynamics, rice yield, and its components, soil and plant samples were collected from seven newly reconstructed fields in Japanese Andosols in Tochigi, Japan. Samples were obtained from both the former low- and high-elevation sides within each field plot. During harvest season, nine rice plants were randomly selected from each plot (0.675 m2, comprising 3 rows and 3 hills per row), collected from a 3-m stretch along both the east (former low side) and west (former high side) ridges. Soil cores were collected from identical plots at two depths (0–15 and 15–30 cm) and combined into one composite sample per layer. Rice plant samples were air-dried for two weeks until reaching constant moisture content, after which stems and ears were separated and weighed to determine biomass, yield, yield components, and nitrogen uptake. This indicated that land reconstruction significantly affected rice yield and its components between the two sides of all field plots. SOC, TN, and their decomposition following land reconstruction showed notable changes, especially in the 15–30 cm subsurface soil layer. Additionally, grain weight demonstrated significant correlation with SOC, TN, and carbon decomposition in both the 0–15 and 15–30 cm layers, indicating that soil fertility to a depth of 30 cm was crucial for rice productivity after land reconstruction.

Rapidly improving infertile croplands and enhancing their soil organic carbon (SOC) pool necessitate substantial organic materials incorporation. Converting loose crop straw into granulated form facilitates uniform incorporation within the plough soil layer. As an innovative soil amelioration approach, the efficiency and patterns of SOC accumulation remain unclear. Two field experiments were conducted in infertile subtropical upland and paddy soils with 0, 30, 60, and 90Mg ha⁻¹granulated straw incorporation. After one year, SOC accumulation efficiency from straw input remained stable in upland (30.8–37.5%) with increasing amounts of straw incorporation, while declined from 60.0 to 38.3% in paddy. In both croplands, the contributions of lignin phenols to SOC increased with increasing straw incorporation, while the contributions from amino sugars remained constant at higher straw input levels. Subsequently, the ratios of lignin phenols to amino sugars increased with increasing straw incorporation, indicating faster plant residue accumulation compared to microbial necromass, as the granulation approach limited microbial involvement in straw transformation. Thus, single-time incorporation of substantial granulated straw presents an effective agricultural strategy for rapid amelioration of infertile croplands.

Phosphorus (P) is an essential nutrient element that is critical for plant growth and ecosystem functionality. The soil P cycle plays multiple roles, such as sustaining plant growth and productivity, regulating nutrient balance within ecosystems, and enhancing ecosystem adaptability and resilience. This cycle is influenced by factors such as the restorationapproachand microbial community dynamics. However, the extent to which the restorationapproach alters the P cycle in karst ecosystems and the underlying microbial mechanisms remain poorly understood. The P-cycle multifunctionality index (P-cycle MFI) serves as a comprehensive indicator for evaluating soil P cycle function, and it provides insights into changes in the P cycle betweendifferentrestorationapproaches. To investigate the shifts in soil P-cycle MFI and microbial mechanisms betweendifferentrestorationapproaches, we analyzed soil available P (AP), total P (TP), microbial biomass P (MBP), and the activities of acid phosphatase (ACP) and alkaline phosphatase (ALP). These data were used to calculate the P-cycle MFI by averaging the Z-scores between tworestoration approaches(artificial restorationof forest(AF)and natural restoration offorest (NF))and a control(cropland, CP) at six subtropical karst ecosystem sites in China. We also determinedthe soil organic carbon (SOC), exchangeable calcium (Ca) and magnesium (Mg), pH, bulk density(BD), microbial biomass C(MBC), and microbial biomass nitrogen (MBN), as well as thecommunity structure,relative abundance, diversity indices, and co-occurrence networks of phoD-harboring bacteria. The results showed that the community structureofphoD-harboring bacteria variedsignificantly among AF, NF, and CPand across differenttemperature gradients. Thesebacteria exhibited increasingcomplexityandtightness in co-occurrence networks from CPto AFand then to NF, along with the ACP and ALP activities,but notthe TP and AP contents. The P-cycle MFI values were significantly higher in NF compared to AF and CP, and the variation was significantly explained byrestoration approach, temperature, MBC, MBN, SOC, exchangeable Ca, BD, community structure ofphoD-harboring bacteria, and exchangeable Mg. Furthermore, natural restoration had a more substantial impact on the P-cycle MFI than temperature by enhancing SOC, microbial biomass, the complexity and co-occurrence network tightness of the phoD-harboring bacterial community structure, and ACP and ALP activities, but it reduced soil BD. The rare genera of phoD-harboring bacteria significantly influenced the variation of soil P-cycle MFI compared to the dominant genera. This study highlights the importance of rare genera of phoD-harboring bacteriain driving soilP-cycle multifunctionality in karst ecosystems, with natural restoration being more effective than artificial methods forenhancing soil organic matter and microbial community complexity.

Fungi play crucial roles in nutrient acquisition, plant growth promotion, and the enhancement of resistance to both abiotic and biotic stresses. However, studies on the fungal communities associated with peas (PisumsativumL.) remain limited. In this study, we systematically investigated the ecological effects of host niches (soil, root, stem, leaf, and pod) and genotypes on the diversity and composition of fungal communities in peas using a multi-level approach that encompassed pattern recognition (β-diversity decomposition), mechanism validation (neutral community model testing), and dynamic tracking methods (migration pathway source-tracking). The results revealed that the dominant fungal phyla across niches and genotypes were Ascomycota, Basidiomycota, and Mortierellomycota, and the community structures of the soil–plant continuum were primarily determined by the pea niches rather than genotypes. β-diversity decomposition was largely attributed to species replacement rather than richness differences, indicating strong niche specificity and microbial replacement across microhabitats. Neutral model analysis revealed that stochastic processes influenced genotype-associated communities, while deterministic processes played a dominant role in niche-based community assembly. Source-tracking analysis identified niche-to-niche fungal migration, with Erysiphe, Fusarium, Cephaliophora, Ascobolus, Alternaria, and Aspergillusas the key genera. Migration rates from exogenous to endogenous niches were low (1.3–61.5%), whereas those within exogenous (64.4–83.7%) or endogenous (73.9–96.4%) compartments were much higher, suggesting that the pea epidermis acts as a selective barrier that filters and enriches microbial communities prior to internal colonization. This study provides comprehensive insights into the mechanisms of host filtering, enrichment and microbial sourcing, which increases our understanding of the assembly rules of the pea-associated fungal microbiome.

Soil organic carbon (SOC) dynamics significantly influence ecosystem carbon source-sink balance, particularly in agroecosystems. However, uncertainty remains regarding optimal land use types for maximizing farmland carbon storage across different soil types, and identifying effective land management practices for enhanced carbon accumulation is essential for reducing agricultural emissions and strengthening carbon sinks. This study examined SOC variations in eastern Yunnan’s subtropical highlands (2,132 sites), analyzing topsoil (0–20cm) across five land uses (dryland, irrigated land, forestland, grassland and plantation) of five soil types (red, yellow, yellow-brown, brown, purple). The investigation explored relationships between SOC and edaphic factors (26 elements) to determine SOC influencing factors. The study area demonstrated a mean SOC content of 27.78g kg^–1, with distinct spatial heterogeneity characterized by lower values in the southwestern sector and higher concentrations in the northeastern region. Brown soils displayed the highest SOC content (P<0.05), followed by yellow-brown then red, yellow, and purple soils. Irrigation significantly enhanced SOC storage, particularly in brown soils where irrigated land contained 2.2-, 2.4-, and 1.6-times higher SOC than forestland, grassland, and dryland, respectively. Similar irrigation benefits occurred in purple, yellow, and yellow-brown soils, indicating moisture limitation as the primary SOC constraint. Notably, SOC exhibited strong positive correlations with nitrogen, sulfur, and selenium. Nitrogen fertilization demonstrated dual benefits: enhancing SOC sequestration and promoting Se enrichment in crops, potentially supporting specialty agriculture. Although land use impacts on SOC varied across soil types (P>0.05), irrigation consistently emerged as the optimal management for carbon sink enhancement. These findings suggest that targeted water management could effectively reduce farmland carbon emissions in moisture-limited subtropical highlands. Strategic nitrogen application offers co-benefits for soil fertility and selenium biofortification, providing practical pathways for climate-smart agriculture in similar ecoregions.

Microorganisms carrying cbbL, pmoAand coxLgenes play crucial roles in regulating soil-atmosphere exchanges of carbon trace gases (CO₂, CH₄, and CO). However, the geographical distribution patterns of these functional genes in agricultural ecosystems and their environmental drivers remain poorly understood. Here, we surveyed agricultural soils across four climate zones (tropical, subtropical, warm temperate, and mid-temperate) in eastern China to quantify the abundances of CO₂-assimilating bacteria (cbbLgene), methanotrophs (pmoAgene), and CO-oxidizing bacteria (coxLgene). We found significant ecosystem-specific patterns: the cbbLgene was more abundant in upland soils (averaging 9.46×10⁹ copies g^–1) than in paddy soils (6.44×10⁹copies g^–1). In contrast, methanotrophs abundance was 1 to 3 orders of magnitude higher in paddy (averaging 1.17×10⁸copies g^–1) than in upland (5.78×10⁶ copies g^–1) soils. The coxLgene maintained similar abundance levels across both soil types (averaging 6.12×10⁸vs. 5.91×10⁸copies g^–1).Structuralequation models revealed that spatial factors primarily shaped cbbLand pmoAin uplands, whereas total bacterial abundance was the dominant predictor for all three genes in paddy soils. These results highlight distinct ecological controls on microbial functional groups and provide a predictive framework for how land use and climate change may regulate microbial mediation of carbon gas fluxes across a continental-scale transect in eastern China.