The soils of alpine meadows on the Tibetan Plateau act as significant carbon reservoirs and are particularly vulnerable to warming. Nevertheless, the long-term (≥20 years) warming impact on SOC composition and deep soil dynamics in alpine meadows remains unclear. This study explored the effects of two decades of warming using open-top chambers on various aspects of alpine meadow ecosystems, including plant community composition and biomass, soil physicochemical characteristics, microbial communities, and SOC content in both bulk soil and its fractions. Prolonged warming had no impact on plant-derived C inputs, as indicated by both unchanged above- and below-ground biomass, but it reduced the light fraction carbon (LF-C) in the surface soil layer (0−10 cm) by 25%, with no notable changes observed in bulk SOC or heavy fraction carbon (HF-C) in the surface soil as well as deeper soil layers (10−50 cm). Additionally, long-term warming caused a notable rise in fungal-derived residues and an increase in aromatic carbon, while concurrently decreasing alkyl carbon in the surface soils. These findings imply that prolonged warming acce-lerates the breakdown of more readily decomposable organic matter, shifting the SOC pool towards a more chemically resistant state, even though there was no net change in bulk SOC.

Tropical forests exert the largest influence on the global carbon (C) cycle and climate, and soil microorganisms play an essential role in the feedbacks of the global C cycle and climate. However, the issue of how nutrient limitation of microbial metabolism affects the soil C cycle and its responses to climate change in tropical forests remains poorly understood. Here, we investigated the elevational patterns of microbial metabolic limitations in typical tropical forests by studying ecoenzymatic stoichiometry along three elevation gradients (with an overall elevation range of 100−1400 m above sea level (a.s.l.)) in south China. Results showed that microbial metabolism in tropical forest soils was strongly limited by phosphorus (P) and increased with increasing elevation, suggesting that there was greater microbial P limitation where temperatures were lower. In contrast, microbialC limitation was relatively low and did not show a consistent elevational pattern. Temperature emerged as the most significant predictor of microbial metabolic limitations, showing a positive correlation with microbial C limitation but a negative correlation with microbial P limitation. Based on an investigation of three topical forest elevation gradients (< 1500 m a.s.l.), our findings predict that global warming may alleviate microbial P limitation while exacerbate microbial C limitation.

Ammonia-oxidizing archaea (AOA) are key drivers of soil nitrification, but how they respond to climate warming across northern China’s diverse grassland types remains unclear. To address this, we analyzed 88 soil samples from 22 sites across three northern China grassland biomes based on metagenomic data, quantifying AOA temperature sensitivity as the regression slope of diversity indicators against mean annual temperature (MAT). Our results revealed MAT as the key factor influencing the relative abundance, richness, and composition of the potential AOA community. In alpine grassland, AOA communities exhibited the highest temperature sensitivity, with the steepest slopes of community composition and relative abundance, and a unique decrease in richness. This high sensitivity may reduce the AOA community diversity and destabilize nitrogen cycling in alpine grasslands. Structural equation modeling indicated that MAT impacted AOA communities via a direct route rather than indirect routes. These findings provide a scientific basis for assessing the potential risks of climate warming on grassland nitrogen cycling and informing early-warning and management strategies.

The physicochemical protection of soil organic carbon (SOC) by iron (Fe) (hydr)oxides and clay minerals is crucial to SOC preservation. While clay minerals restrict SOC mineralization, a lack of information exists on the regulatory mechanisms by which clay minerals and their interactions with Fe (hydr)oxides regulate the priming effect (PE). Here, we quantified the PE intensities in two forest soils (i.e., a sandy loam soil and a loam soil), amended without or with Fe (hydr)oxides (goethite) at two levels. The loam soil containing higher clay minerals showed a 26% lower SOC mineralization but a 28% greater PE than the sandy loam soil. This is likely because SOC encapsulated within clay particles serves as a substrate reservoir, which can be decomposed by activated microbes following exogenous C inputs. Contrasting goethite effects on the PE in different soils were detected. High goethite addition intensified the PE in sandy loam soil, while the PE in loam soil declined at both levels of addition. The underlying mechanisms were attributed to alterations in Fe-mediated co-precipitation situation and subsequent microbial metabolism. Overall, this study demonstrates a crucial role of clay minerals in SOC stabilization, with implication for soil management with Fe (hydr)oxides.

Soil microbial necromass carbon (MNC) plays a crucial role in the persistent soil organic carbon (SOC) pool. However, the impact of long-term different water-nitrogen managements on the soil MNC in the greenhouse vegetable production (GVP) remains unclear. Using a 12-year field experiment, coupled with soil physicochemical properties, C- and nitrogen (N)-related enzymatic kinetics and microbial communities’ measurements, the impact of six different water-nitrogen managements on MNC accumulation was examined. Our study showed that MNC constituted 47.7%–71.3% of SOC, with fungal necromass carbon (FNC) contributing 4.2-fold more than bacterial necromass carbon (BNC) on average. Compared to the high irrigation and chemical nitrogen fertilizer practices, water-saving practices under the high fertilization scenario increased BNC/SOC by 18.6% after the 12-year field manipulation. The reduced water-N treatments had the highest MNC/SOC proportions with an average of >60%, which was mainlyattributed to the increased FNC/SOC. The relative importance partitioningresults showed that root biomass, N-acetylglucosaminidase and C-cellobiohydrolase enzyme kinetics were the most important regulators of FNC/SOC, BNC/SOC and MNC/SOC, respectively. The partial least squares path modeling further revealed that soil substrates (e.g., root biomass and dissolved organic carbon) directly promoted FNC/SOC while suppressing BNC/SOC, whereas microbial communities enhanced both fractions. Hence, our study highlights the divergent response of FNC and BNC to the long-term water-nitrogen management in GVP. Therefore, optimized water-nitrogen management sustains crop productivity while enhancing MNC accumulation, thereby promoting SOC persistence and advancing green sustainable development of GVP.

Soil nematodes show the highest abundance among animals on Earth, which can affect plant residue decomposition by influencing plant roots and soil microbes, thus affecting plant- and microbial-derived carbon (C) sequestration. However, the relationships between soil nematodes, plant- and microbial-derived C under long-term fertilization remain unclear. The present work performed a 15-year field fertilization experiment (including four treatments: (1) no fertilizer (CK); (2) nitrogen, phosphorus, and potassium fertilizers (NPK); (3) NPK with straw (SNPK); and (4) NPK with pig manure (MNPK)) for investigating how soil nematodes affected soil plant- and microbial-derived C by determining soil nematode, bacterial, and fungal abundances as well as amino sugar and lignin phenol contents (their biomarkers), and their associated relationships. The results revealed that SNPK treatment increased the abundances of soil bacterivores and bacteria as well as the bacterial necromass C (BNC) content. As revealed by partial least squares path modeling (PLS-PM), bacterivores showed indirect and positive impacts on BNC through influencing the abundance of bacteria. Moreover, SNPK treatment increased fungal abundance and fungal necromass C (FNC) content but did not alter fungivore abundance. FNC was significantly and positively correlated with fungal abundance and bacterivore abundance. PLS-PM revealed that BNC indirectly influenced FNC by affecting fungal abundance; thus, bacterivores play an important role in affecting FNC by affecting BNC. Moreover, all the fertilization treatments increased the lignin phenol content, which was significantly and positively correlated with the bacterivore and plant parasite abundances, indicating that the elevated bacterivore and plant parasite abundances during fertilization may contribute to the formation of plant-derived C. Overall, these findings provide insights for developing fertilization strategies that utilize nematode-mediated C pathways to enhance soil C sequestration in agricultural systems.

Water availability and soil microbes critically influence plant survival and health in extreme desert ecosystems. Here, we investigated the dynamic changes in soil microbial traits associated with healthy and unhealthy Populus euphratica trees at varying distances from the river, while also examined the assembly mechanisms and ecological relationships between biotic and abiotic drivers. The results revealed nonlinear responses of microbial traits—including diversity, composition, functions, and network structure—to river proximity, exerting stronger effects than tree health status. Dominant and key taxa, as well as functions, differed between healthy and unhealthy trees. Mycorrhizal fungi were enriched in healthy stands, peaking at 4 km, while saprotrophic and parasitic fungi were more abundant in unhealthy stands, peaking at 6 km. Both healthy and unhealthy trees exhibited enrichment in primary bacterial functional categories—metabolism, environmental information processing, and cellular processes; however, differed in tertiary functional composition. Fungal networks were less complex than bacterial networks, though both were dominated by positive interactions. Community assembly for both fungal and bacterial communities was primarily driven by stochastic dispersal limitation. Soil available phosphorus, pH, grass cover, and litter cover were identified as critical ecological factors, regulating fungal and bacterial traits via distinct pathways. Biotic and abiotic interactions accounted for 42%‒72% of fungal and 68%‒84% of bacterial traits variation. β-diversity exhibited strong and contrasting effects on fungal and bacterial functional traits. Network intensity significantly positively influenced specific bacterial functional traits. These findings provide a theoretical foundation for understanding microbial adaptation mechanisms and ecological restoration in arid riparian forests.

Salinity adversely impacts soil ecosystems, by inducing osmotic stress, ionic imbalances, water deficit, and oxidative damage in plants. It also alters the composition of plant-associated microbial communities in the rhizosphere and roots, while disrupting microbial processes critical to nutrient cycles. Aloe vera (Aloe barbadensis Miller), a xerophytic succulent plant, produces acemannan, a bioactive polysaccharide in its leaf gel with pharmaceutical applications. Acemannan contributes to drought tolerance by facilitating water storage within the leaf gel tissue. This study examined the effects of soil salinity on rhizosphere properties, plant nutrient acquisition, acemannan accumulation, and plant-associated microbial communities in A. vera plants grown in the field in Laconia, Greece. Both acemannan and sodium (Na) accumulated in the leaf gel in response to soil salinity, showing a strong positive correlation. Significant differences in the composition and structure of the rhizosphere and root microbial communities were also observed under salinity, with the prokaryotic microbial community in the plant roots showing a pronounced shift towards functionally relevant membership and abundance of monoderms. Moreover, we observed significant co-variation of changes in the acemannan and Na concentrations in the leaf gel with changes in the prokaryotic rhizosphere soil community and the fungal community in the roots. Our findings demonstrate enhanced accemanan production and indicate links between osmolyte accumulation and microbial community adaptation in A. vera under soil salinity.

Effective crop residue management is crucial for phosphorus (P) cycling in agricultural ecosystems, yet the underlying mechanisms of various residue return strategies remain inadequately understood. This study presents the initial three-year results from a long-term field experiment in northeast China comparing four maize residue management practices: conventional ridge tillage without residue return (DT), no-tillage with surface residue retention (NT), three-year rotational tillage with depth-variable (15/20/35 cm) residue incorporation (VT), and annual deep tillage (0–35 cm) with residue incorporation (AT). Results demonstrated distinct depth-stratified impacts on soil phosphatase activities and P fractions. NT significantly enhanced the sum of phosphodiesterase (PDase), alkaline phosphomonoesterase (AlPase), and acid phosphomonoesterase (AcPase) activities by 26.0% compared to DT in surface soil (0–10 cm), increasing labile inorganic P accumulation by 16.9% compared to DT. Conversely, VT and AT increased phosphatase activities by 24.9% compared to DT and NT at 10–35 cm depths, with VT enhancing labile organic P conservation by 71% at intermediate depths (10–35 cm) and AT primarily increasing moderately labile organic P conservation by 465% in deeper soil (20–35 cm) compared to DT. Structural equation modeling revealed that NT and VT employed more diverse P regulatory pathways than AT and DT, suggesting greater functional resilience. This study establishes three-year rotational tillage as an optimal strategy for P conservation and availability throughout the plow layer while minimizing environmental losses, providing critical insights for sustainable agroecosystem management.

Understanding the relationship between soil microbial diversity and ecosystem multifunctionality is crucial for predicting ecosystem responses to environmental changes. In this study, an investigation was conducted into soil samples collected from 20 sites across five grassland types situated along an altitudinal gradient spanning 2300 m within the Tianshan Mountains, China. Microbial co-occurrence networks were constructed based on bacterial and fungal communities, with their complexity quantified using network topological features. The results revealed a significant variation in microbial diversity and network complexity across the aridity gradient. Bacterial α-diversity (Shannon index) unexpectedly showed a negative correlation with soil multifunctionality, likely reflecting intensified potential competitive associations and dominance of drought-tolerant specialists under arid conditions, whereas fungal diversity showed a weaker link. Microbial co-occurrence networks showed elevated connectivity and reduced modularity in arid regions, with potential competitive associations being dominated under water scarcity. Keystone taxa (species critical to network stability), such as Actinobacteria and Zygomycota, were identified as key players in maintaining ecosystem functions across different grassland types. Structural equation modeling (SEM) indicated that bacterial diversity and network complexity were negatively associated with soil multifunctionality. This study emphasizes the critical role of microbial networks in sustaining ecosystem functions along aridity gradients. It offers insights into management strategies towards enhancing soil multifunctionality, particularly in the context of climate change adaptation.

Nano-engineered amendments, such as nano zero-valent iron-modified biochar (nZVI-BC), offer promising potential for restoring degraded soils; however, their role in regulating soil carbon cycling, particularly under climate warming conditions, remains insufficiently understood. This study evaluates the effects of nZVI-BC and yak dung biochar (BC), applied at 1% and 5% (w/w), on soil organic carbon (SOC) dynamics in degraded alpine grasslands. Biochar was incorporated into three soil aggregate size fractions (< 0.25 mm, 0.25–2 mm, and >2 mm), and soils incubated at 5 °C and 15 °C for 28 days to measure SOC mineralization, priming effect, and temperature sensitivity (Q₁₀). When the temperature increased from 5 °C to 15 °C, SOC mineralization in all soil aggregate sizes significantly increased, with priming effects showing a positive enhancement and peaking under the 5% nZVI-BC treatment. Both types of biochar effectively enhanced SOC mineralization across most aggregate sizes and generally increased Q₁₀ values; however, in large macroaggregates, mineralization under the 5% nZVI-BC treatment was no longer at its peak, and its Q₁₀ value markedly decreased relative to the control. The study indicates that the effect of biochar on SOC mineralization is regulated by the interaction between aggregate size and temperature, with large macroaggregates being crucial for SOC sequestration. This highlights the potential of nZVI-BC in modulating soil carbon cycling and aggregate stability in cold-region soils. Leveraging the high reactivity of nZVI, future research could explore the co-benefits of nZVI-BC in synergistically enhancing soil carbon sequestration and remediating soil pollutants, thereby optimizing its ecological value and sustainable application in alpine ecosystems.

Plants can enhance their resistance to pathogens by regulating their associated microbial communities, which contributes to the ecological adaptability and potential application of afforestation species. However, microbial interactions in the rhizosphere and roots, and their implications for pathogen suppression in afforestation systems, remain unclear. In this study, we investigated the structure and potential functions of bacterial and fungal communities in roots, rhizosphere soil, and bulk soil of major afforestation species in northeastern China, Birch, Larch, and Poplar, using amplicon sequencing, with a particular focus on associations among functional microbial groups. In rhizosphere soils, the relative abundance of ectomycorrhizal (EcM) fungi was negatively correlated with that of pathogenic fungi in Birch and Larch forests. In roots, the relative abundance of saprotrophic fungi was negatively correlated with that of pathogenic fungi across all tree species. In contrast, major bacterial genera showed no consistent associations with pathogen abundance across compartments. Additionally, Larch forests showed a greater influx of bacterial and fungal taxa from the rhizosphere into the roots, yet root pathogen abundance remained comparatively low. These results suggest that negative associations between pathogenic fungi and EcM fungi in the rhizosphere, together with compartment specific microbial filtering and negative associations with saprotrophic fungi within roots, may contribute to reduced abundance of pathogenic fungi particularly in Larch. These results highlight the potential role of host-associated microbial community structure in mediating pathogen pressure and enhancing the ecological adaptability of afforestation species.

Most terrestrial plants acquire substantial amounts of mineral nitrogen (N) via associated arbuscular mycorrhizal fungi (AMF). These fungi, in turn, rely on hyphosphere microorganisms to release N in the forms of ammonia (NH₄⁺) and nitrate (NO₃^–) via organic matter decomposition. The stability of hyphospheric microbiomes is crucial for sustaining N supply, yet how these communities respond to different inorganic-N forms remains poorly understood. To address this, we conducted a greenhouse pot experiment using a model plant-mycorrhizal system consisting of Asiatic plantain and Funneliformis geosporum. We find that the addition of inorganic-N at a moderate agronomic dose (60 mg N kg⁻¹), regardless of its form, led to a shift in microbial community composition and a critical decrease in network complexity of the hyphospheric microbiomes. Notably, microbial community composition within the AMF hyphosphere exhibited high resilience, with its recovery rate reaching up to 92% (indexed by Bray−Curtis and Jaccard similarities) following AMF-mediated N depletion. By contrast, the interaction network of hyphospheric microbiomes displayed relatively lower resilience (64%), with the number of nodes and links progressively declining after N addition, largely due to disrupted associations between dominantand rare taxa. Whether this network state represents a persistent impairment or atransient stage requires further investigations on the basis of longer-term experiments. Our findings reveal an asynchronous resilience pattern of microbial community composition and network complexity within the AMF hyphosphere, offering an insight into the stability of soil microbiomes under fertilization in agricultural ecosystems.