Biochar has emerged as a nature-based solution to restore degraded drylands; however, its effects on soil microbiomes in semiarid and desertification-prone environments remain less understood. Here, we evaluated how biochar origin and application influence the structure of bacterial communities in a highly degraded Planosol from the Brazilian Caatinga biome. A controlled experiment was conducted using two biochar types, cashew bagasse-derived biochar (CB) and sewage-sludge biochar (SSB), applied at four doses (5, 10, 20, and 40 Mg ha⁻¹), plus an unamended control (0 Mg ha⁻¹), followed by 90 days of maize cultivation. Biochar changed bacterial community composition, with the emergence of distinct microbial assemblages depending on biochar type and dose. A single low dose (5 Mg ha⁻¹) of biochar was sufficient to enhance bacterial richness and Shannon diversity, while SSB promoted the dominance of stress-tolerant taxa (e.g., Bacillus). Functional prediction and co-occurrence networks revealed that CB promoted functions related to nitrogen cycling and chemoheterotrophy, whereas SSB favored metal-tolerant and hydrocarbon-degrading taxa. Network complexity increased with biochar addition, especially at intermediate SSB doses. Overall, CB promoted more stable ecological responses, while sewage-sludge biochar caused stronger shifts. Our results demonstrate that biochar origin and application rate are critical to microbial restoration, i.e., moderate doses stimulate diversity, ecological specialization, and soil multifunctionality, whereas higher inputs, especially of nutrient- and metal-rich biochars, may compress functional traits. Plant-derived biochars, particularly CB, demonstrated potential for restoring soil bacterial structure and resilience in degraded semiarid landscapes when applied at appropriate rates.

Ecosystem degradation restructures soil microbial interaction networks, yet the mechanistic pathways linking network topology to functional decline remain poorly understood. Here, we investigate how grasslandification, that is, “the conversion of alpine wetland meadows into degraded meadows,” alters cross-domain microbial networks across soil depths and plant root compartments on the Tibetan Plateau. Using integrated network analysis, multivariate modeling, and structural equation models (SEMs), we demonstrate that grasslandification drives a systematic restructuring of network architecture through declining connectivity and environmental filtering via soil chemistry and microbial biomass. These networks progressively lost connectivity and became more modular, indicating fragmentation into isolated functional modules with reduced synergistic interactions. Network robustness declined substantially, rendering degraded communities more susceptible to perturbations. Cross-domain ana-lyses revealed that vertical connectivity between soil layers remained intact despite surface degradation, while plant-associated networks became more sensitive, with disrupted rhizosphere-rhizoplane interactions. Keystone taxa shifted from fungal connectors in pristine meadows to bacterial module hubs in degraded meadows, signifying fundamental changes in community assembly. The SEMs highlighted that grasslandification affected soil multifunctionality mainly through indirect pathways mediated by soil chemistry and microbial biomass, while the direct effects of network topology were comparatively weak. This suggested that network changes represent emergent indicators of ecosystem state transitions rather than principal direct drivers of functional loss. We conclude that microbial network restructuring co-occurs with multifunctionality loss during grasslandification, and that network metrics provide early-warning indicators for ecosystem degradation in alpine regions under environmental stress.

Balancing timber production with biodiversity conservation is challenging. Collembola, a key soil mesofauna group, contribute significantly to forest ecosystem functioning and bioindication. We examined long-term, seasonal effects of four management treatments, gap-cutting (G), clear-cutting (CC), retention tree group (R), and preparation cutting (P), in an 80-year-old oak forest, with untreated controls (C), after five and eight years. Collembola responses differed by ecomorphological group and season. Epigeic densities were lowest in G plots after five years but recovered in the eighth year. Hemiedaphic forms were most abundant in C plots, while G and CC plots remained reduced. Euedaphic Collembola responded in the fifth year, particularly in R during spring, but differences largely disappeared by the eighth year. By year eight, G supported the most diverse and even communities, whereas diversity declined in C and R plots. Seasonal differences were strongest in spring but weakened over time. Our findings highlight Collembola’s capacity to recover after disturbance, supporting their use as indicators of ecological recovery. Treatments with limited canopy opening: G and P maintained community structure and enhanced diversity. As succession advanced, vegetation structure became a stronger driver than soil or seasonal factors. Collembola inform monitoring of forest regeneration and guiding sustainable management.

Sedimentary dissolved organic matter (DOM) plays a critical role in carbon cycling in arid inland river systems, yet its spatial variability and associated environmental factors remain poorly understood. Herein, we investigated the spatial heterogeneity of sedimentary DOM along the Niya River Basin (northwestern China) using optical spectroscopy coupled with PARAFAC modeling and multivariate statistical analyses. Results showed that DOM exhibited weak vertical differentiation but pronounced longitudinal heterogeneity along the upstream to downstream gradient. Six fluorescence components were identified, including humic-like and protein-like substances derived from terrestrial inputs and microbial processing. Upstream sediments were dominated by terrestrially derived DOM, whereas midstream and downstream regions reflected combined influences of hydrological transport and microbial transformation. Statistical analyses showed that grain-size parameters, including sand content and mean grain size, together with sediment physicochemical indicators such as TOC, TN, NH₄⁺, pH, and electrical conductivity, were strongly associated with variations in DOM composition. Hydrological conditions may also be indirectly linked to DOM variability through their covariance with sediment properties. Overall, our findings highlight that hydrological conditions and multi-factor associations are closely related to sedimentary DOM variability in arid inland rivers, providing new insights into carbon cycling and ecosystem functioning in water-limited environments.

Labile carbon availability can greatly affect the soil organic carbon (SOC) decomposition through priming effect (PE). However, the effects of temperature on CO₂ emissions, PE, and the underlying mechanisms in forest soils along urban-rural gradient are still unclear, which will induce uncertainties in the prediction of terrestrial-climate feedbacks during urbanization. In this study, we thus performed a 35-day incubation experiment using ¹³C-labeled glucose, with soils collected from urban, suburban, and rural forests to test effects of labile C addition on priming and the temperature sensitivity (Q₁₀ values) of SOC decomposition. Results showed that the cumulative CO₂ emissions were significantly increased with increasing glucose addition and rising temperature, which exhibited a decreasing trend from urban to rural forest soil. CO₂ emissions from native rural soil were obviously lower than that of urban and suburban soils at the end of the incubation regardless of temperature. Cumulative primed C increased with the amount of glucose added, and the values at 25 °C (suburban soil with low glucose addition excepted) were significantly higher than that at 15 °C. The magnitude of the positive priming declined along the urban-rural gradient soils incubated at 15 °C. There were no significant differences in the Q₁₀ values of SOC decomposition during incubation, which were significantly decreased after glucose addition. Redundancy analysis indicated that Gm‒ (18.97%), Gm+/Gm‒ (18.02%), and bacteria (11.28%) accounted for most of the variation in CO₂ emissions at 15 °C. Whereas at 25 °C, the ratios of F/B (23.27%), Actinomycetes (21.07%), and Gm‒ (17.51%) had higher explanatory power, suggesting the different roles of microbial group in SOC decomposition at varied temperature. Our results provide novel insights into forest soil carbon cycling mechanisms that mediating soil-climate feedbacks in the context of rapid urbanization and global warming.