Biochar has emerged as a promising carrier for microbial inoculants, yet its capacity to enhance inoculant persistence while preserving native soil microbial communities remains insufficiently documented. This study evaluated an olive-pomace-derived biochar as a carrier for Bacillus velezensis and Trichoderma virens in a Mediterranean Cambisol under controlled conditions. Biochar supported high initial microbial loadings (>108 CFU or spores g−1 biochar), strong short-term viability (76–88%), and clear colonization of pore surfaces as observed by scanning electron microscopy. Following a 30-day pot incubation, biochar-based inoculation enhanced microbial persistence compared with direct soil application, maintaining recoverable inoculant populations close to or above initial levels. Findings revealed that biochar maintained community-level structural and functional patterns at the resolution detectable by fingerprinting and metabolic profiling approaches. These results suggest that biochar functioned primarily as a physical carrier, providing protected microsites that may have contributed to the stabilization of introduced microorganisms while maintaining overall soil functional diversity. Our findings demonstrate that olive-pomace biochar can be valorized as an effective microbial carrier, suited to Mediterranean soils where early inoculant establishment is often constrained. Future research should assess the durability of these mechanisms under field conditions to determine their long-term relevance for soil biological functioning and restoration.
Coastal wetlands are experiencing long-term plant invasions, which pose a significant impact on the soil microbiome. However, the latitudinal diversity patterns of soil microbiome in blue carbon ecosystems under plant invasion remain poorly understood. In this study, 12 sample sites spanning over 2000 km were established along China’s coastlines, with paired mudflat and Spartina alterniflora-invaded habitats. Soil (mudflat sediments included, termed “soil” for consistency) bacterial diversity was assessed across topsoil, subsoil, and deep soil layers. In mudflat habitats, bacterial richness generally increased with latitude. In contrast, S. alterniflora invasion altered this pattern to a hump-shaped distribution. This shift was most pronounced in the topsoil compared to the subsoil and deep soil layers, a consistent trend across the dominant taxa. Additionally, plant invasion accelerated the spatial turnover of bacterial communities in the topsoil, but not in deeper layers. Environmental variables, including soil temperature and salinity, were the predominant factors shaping these latitudinal diversity patterns. Structural equation models revealed that soil temperature, rather than soil depth, was the primary direct driver of bacterial richness, and plant invasion reduced the influence of soil depth on this relationship. Overall, our study revealed that invasive plant regimes profoundly restructured the latitudinal diversity pattern of soil microbiomes, particularly in the topsoil. This study broadens our understanding of how plant invasion affects soil microbial biogeography and its underlying drivers in blue carbon ecosystems.
Drylands are crucial to global biogeochemical cycles, yet the linkages between soil multifunctionality (SMF) and microbial diversity, community assembly, and network architecture remain poorly understood. Here, we investigated these relationships across three grassland types—desert steppe, temperate desert, and temperate steppe—in the drylands of Kazakhstan. Despite contrasting environmental conditions, microbial α diversity did not differ significantly among grassland types and was more strongly associated with climatic factors than with grassland type per se. Fungal and bacterial communities exhibited distinct assembly patterns. Fungal communities were governed by dispersal limitation (57.46%–57.69%) and homogeneous selection (13.16%–16.40%), with community similarity correlated with both environmental and geographic distances. In contrast, bacterial communities were shaped predominantly by ecological drift (40.38%–42.88%), and their similarity was linked primarily to geographic distance. Microbial co-occurrence network also varied systematically across grassland types, shifting from more modular structures in desert steppe to more connected configurations in temperate desert and temperate steppe. Structural equation modeling showed that climatic variables, particularly mean annual temperature, exerted the strongest direct effects on SMF, whereas community assembly processes influenced SMF only indirectly through their regulation of microbial diversity. Overall, climatic gradients, rather than microbial richness per se, emerged as the primary correlates of SMF, with fungal and bacterial communities exhibiting divergent assembly processes and network organization along the aridity gradient. These findings provide an integrative, association-based framework for understanding how environmental gradients related to aridification correspond to microbial ecological organization and SMF in drylands.
Intensively managed Camellia oleifera plantations with acidified soil rely on nitrogen (N) fertilizers for high yields, but this accelerates soil acidification and boosts emissions of nitric oxide (NO) and nitrous oxide (N2O), endangering long-term sustainability. Green manure (GM) serves as an eco-friendly alternative, improving soil fertility and increasing ecosystem carbon and N inputs. However, the effects of GM species, legumes (Leg), gramineous (Gra), and their mixture (Leg-Gra) with residue incorporation on soil acidification and NO/N2O fluxes remain unclear. To clarify the mechanisms underlying GM intercropping with residue incorporation on soil NO and N2O emissions, we conducted an in situ study in intensively managed C. oleifera plantation ecosystems intercropping Leg, Gra, and Leg-Gra, or managed with N, manual weeding and natural grass to investigate how GM intercropping with residue incorporation influences soil acidification and NO/N2O emissions. 1) GM intercropping with residue incorporation reduced both NO and N2O emission rates compared to N. Specifically, Leg, Gra and Leg-Gra intercropping reduced the emission rates of N2O by 24.83%, 46.06% and 35.64% compared to N, respectively. 2) GM intercropping reduced the abundance of AOA and AOB genes, increases the abundance of nosZ, and decreases NO and N2O emissions. 3) Leg-Gra intercropping with residue incorporation increased soil organic carbon (SOC) by 9.96% and raised soil pH to 4.89, representing a 5.81% increase over N treatment. 4) Leg-Gra increased the decomposition rate of leguminous GM, accelerating nutrient release. Legume-gramineous intercropping effectively mitigates soil acidification, enhances SOC, and curbs NO/N2O emissions, offering a sustainable strategy for acidic agroforestry soils.
Soil gaseous nitrogen (N) losses, including nitric oxide (NO), nitrous oxide (N2O) and dinitrogen (N2), constitute an important component of ecosystem N budgets and strongly influence climate change. However, precisely distinguishing their highly complex production pathways remains a major challenge. Stable N isotope techniques, including 15N tracing and natural-abundance isotopocule approaches, provide critical tools for disentangling these pathways. Over the past two decades, Chinese researchers have developed and refined four major isotope-based source-partitioning methods, mainly including the three-pool source partitioning approach based on paired 15N labeling of NH4+, NO3−, and organic N, the combined 15N paired-labeling and isotope-pairing technique, the 15NO3− labeling and pairing approach coupled with nitrification inhibitors, and the N2O isotopocule site preference (SP) approach. These approaches have been applied in forests and croplands, improving understanding of the relative contributions of denitrification, nitrification, heterotrophic nitrification, codenitrification, and anammox to gaseous N production. This review summarizes the principles, designs, strengths, limitations, and applications of these four N isotope approaches in Chinese ecosystems, highlighting contributions of Chinese researchers to methodological innovation and in situ applications, and providing a China-based perspective for global studies of soil gaseous N losses and methodological support for N cycle model optimization and mitigation strategies.
