Global warming has intensified nitrous oxide (N2O) emissions, heightening the need for climate-smart ecological restoration in drylands. Afforestation is a key strategy for rehabilitating degraded sandy ecosystems, yet how afforestation types interact with global change drives, including variable precipitation and nitrogen (N) deposition to influence soil N2O emissions and their underlying microbial mechanisms remain unclear. This study investigated how afforestation-induced shifts in microbial functional traits regulate N2O emissions under varying water and N availability in semi-arid sandy regions.We conducted a full-factorial incubator experiment using soils from a 35-year restoration site in Horqin Sandy Land, including sand dune (Sd) and five afforestation type: Caragana microphylla (Cm), Populus simonii (Ps), Pinus sylvestris var. mongolica (Pm), and mixed forests (Ps+Pm, Pm+Cm), under two water levels (30% and 60% water holding capacity, WHC) and N addition (0 and 0.02% urea). We measured soil N2O emissions, net N transformation rates, and the abundances of key microbial functional genes. N addition significantly increasing N2O emissions at 60% WHC, with pure forests (Cm, Ps, and Pm) showing the highest emissions, while Pm+Cm consistently showed the lowest emissions. Under N addition and 30% WHC, Ps+Pm exhibited higher net N transformation rates, while Sd remained low rates. N2O emissions correlated positively with NO3--N and NH4+-N accumulation in pure stands and Ps+Pm. Pm exhibited elevated nirS and nirK abundances and lower pH, increasing emission risk, whereas Pm+Cm showed a higher nirS/nirK and lower (nirS+nirK)/nosZ, indicating stronger complete denitrification potential. These finding demonstrate that afforestation types shape microbial functional structure, modulating ecosystem reponses to water and N inputs. Pm+Cm effectively mitigate N2O emissions by promoting complete denitrification, offering a mechanistic basis for designing afforestation strategies to synergistically support ecological restoration and N2O mitigation in semi-arid regions.

To identify a suitable plastic film type for broccoli cultivation in the subtropical humid region of southern China, a field experiment was conducted with four treatments, including no film control (CK), reinforced polyethylene film (RF), biodegradable film PBAT + starch (BDF1), and biodegradable film PBAT + PLA (BDF2). Soil physiochemical properties, temperature and humidity dynamics, microbial community structure, and film degradation status were investigated. The results showed that the RF treatment improved available P and K contents, while the BDF2 treatment significantly increased soil organic matter, NH4+-N, water-soluble Ca2+, and Mg2+ contents. The soil temperature followed the order of RF > BDF1 > BDF2 > CK, and the humidity was BDF1 > RF > CK > BDF2, with RF treatment showing a more stable soil temperature, while BDF2 treatment fluctuated the most. There were no significant differences in bacterial diversity among the treatments, while the highest fungal diversity was observed in the BDF2. Water-soluble Mg was the key factor driving the changes in microbial community structure (p < 0.05). The film degradation rate followed BDF2 > BDF1 > RF. Collectively, RF is suitable for targeting short-term yield improvement, while BDF2 has significant advantages in sustainable cultivation in the long-term.

Livestock grazing has been shown to shape the biodiversity of grasslands, thereby impacting ecosystem stability. Overgrazing may promote the encroachment of shrubs into these habitats through niche partitioning, specifically differences in above-versus below-ground resource usage between woody and herbaceous plants. However, grazing effects on grassland stability remains under-researched, with a paucity of comprehensive empirical studies. In our study, we conducted a seven-year sheep grazing experiment in a desert steppe of northern China. We specifically compared two habitat types: grass-dominated and shrub-encroached, aiming to discern the effects of varying grazing intensities on the stability of aboveground, belowground, and total biomass. Our results indicated that grazing increased the community-weighted mean (CWM) of fast-slow traits and reduced the species asynchrony in grass-dominated habitat, while elevated relative abundance of dominant species and reduced functional dispersion and soil property in shrub-encroached habitat. Increasing grazing intensity diminished the stability of aboveground and belowground biomass within grass-dominated habitat, without significant changes to stability of belowground biomass in shrub-encroached habitat. The CWM Fast-slow traits in grass-dominated habitat and the dominant species abundance of Reaumuria songarica in shrub-encroached habitat were negatively correlated with the stability of aboveground biomass. Thus, while grazing indirectly decreased community stability through elevating CWM Fast-slow traits in grass-dominated habitat, grazing impacted community stability in shrub-encroached habitat via increasing the dominant species abundance of R. songarica, with consequent influences on species asynchrony and stability. Together, our two-habitats experiment highlights the importance of conserving different facets of biodiversity for sustainably providing ecosystem functions and services in arid grazing grasslands.

AbstractsAs global climate change intensifies, nitrous oxide (N2O), a potent greenhouse gas (GHG) has become a central focus for mitigation strategies. Afforestation in semi-arid sandy lands aids ecological restoration, but uncertainties remain about how afforestation types modulate soil nitrogen (N) transformation, N2O emissions, and microbial mechanisms. This gap limits afforestation strategy optimization. Therefore, we conducted a systematic study with the objective of unraveling the mechanisms by which afforestation modulate soil N cycling and N2O emissions in the Horqin Sandy Land. We examined 35yearold artificial forests of six typical types: sand dune (Sd), Caragana microphylla Lam (Cm), Populus simonii Carr (Ps), Pinus sylvestris var. mongolica Litv. (Pm), and mixed forests (Ps+Pm and Pm+Cm). A 60day soil incubation experiment was performed to analyze N transformation, N2O emission characteristics, and N cycling functional genes. Afforestation significantly improved soil fertility, with Ps+Pm showing the highest soil organic carbon and total N, Ps and Pm were N2O emission hotspots, while Pm+Cm reduced emissions. Soil nitrification and denitrification potentials were significantly elevated by afforestation, with increase of 1.10-2.72 times and 5.47-13.37 times, respectively. Functional gene analysis revealed that AOA and AOB abundances were higher in Ps and Ps+Pm, Ps+Pm enriched nirS and nosZ, and Pm+Cm had optimized nirS/nirK and (nirS+nirK)/nosZ. Afforestation regulates N2O emissions though cascading interactions among soil properties, N transformation processes, and microbial functional gene dynamics. Pm+Cm balance soil fertility and N2O mitigation by finely regulating the expression of key microbial functional genes. These findings provide mechanistic support for sustainable afforestation types that integrate ecological restoration and low GHG emissions in semiarid sandy ecosystems.

Study region: Northern China's agro-pastoral ecotone (APE), a semi-arid to semi-humid transitional zone encompassing five major watersheds: Songhua River Basin (SHB), Liaohe River Basin (LB), Haihe River Basin (HB), Yellow River Basin (YB), and Inner Mongolia Endorheic Basin (EB). Study focus: We integrated high-resolution surface water datasets with hydro-meteorological products and land use records to assess impacts on net water yield (NWY). Analysis of surface water dynamics (areas > 1 ha) was conducted using Theil-Sen slope estimation and structural equation modeling. New hydrological insights: The APE experienced marginally significant hydrological aridification during 1986-2020, characterized by net surface water loss (-4140 ha yr(-1), p = 0.052) and declining water body numbers (-158.7 yr(-1), p = 0.092). Watershed trends exhibited pronounced divergence, with the most severe depletion in the LB (-1523 ha yr(-1) and -55.7 water bodies yr(-1)) and moderate declines in the EB (-716 ha yr(-1) and -7.2 yr(-1)), contrasting sharply with significant expansion in the YB (1169 ha yr(-1) and 46.2 yr(-1), p < 0.001). Major lakes/reservoirs underwent a significant shrinkage, with relative water area (RWA) declining at -1.22 % yr(-1) (p < 0.05) and the maximum shrinkage rate in the LB (-3.29 % yr(-1), p < 0.001). A declining aridity index and intensified land use, particularly irrigation expansion and revegetation, amplified evapotranspiration (ET), with cropland areas since 2000 showing average ET increases of 1.9 +/- 2.6 mm yr(-1) (GLEAM) and 6.5 +/- 2.5 mm yr(-1) (MODIS), thereby diminishing NWY across the APE. These divergent watershed trajectories demonstrate that anthropogenic interventions have outweighed climatic drivers to reconfigure surface water distribution. This human-mediated redistribution of water resources necessitates watershed-specific allocation frameworks to secure regional water sustainability.

Global warming has intensified nitrous oxide (N2O) emissions, heightening the need for climate-smart ecological restoration in drylands. Afforestation is a key strategy for rehabilitating degraded sandy ecosystems, yet how afforestation types interact with global change drives-such as variable precipitation and nitrogen deposition-to influence soil N2O emissions and theie underlying microbial mechanisms remain unclear. This study investigated how afforestation-induced shifts in microbial functional traits regulate N2O emissions under varying water and nitrogen (N) availability in semi-arid sandy regions. A full-factorial incubator experiment was conducted using soils from sand dunes (Sd) and five 35-year-old afforestation types: Caragana microphylla (Cm), Populus simonii (Ps), Pinus sylvestris var. mongolica (Pm), and mixed forests (Ps+Pm, Pm+Cm). Treatments included two water levels (30% and 60% water holding capacity, WHC) and two nitrogen addition (0 and 0.02% urea).,We quantified soil N2O emissions, net N transformation rates, and the abundances of key microbial functional genes. N addition significantly increasing N2O emissions in most afforestation types. Pure forests (Cm, Ps, and Pm) under 60% WHC with N addition becoming N2O emission hotspots, whereas Pm+Cm consistently showed the lowest emissions. Ps+Pm exhibited higher net N transformation rates under N addition and 30% WHC, while Sd maintained low rates. N2O emissions correlated positively with NO3--N and NH4+-N accumulation in pure stands and Ps+Pm. Pm had elevated nirS and nirK abundances and lower pH, increasing emission risk, while Pm+Cm showed a higher nirS/nirK and lower (nirS+nirK)/nosZ, indicating stronger complete denitrification potential. These finding demonstrate that afforestation types shape microbial functional structure, modulating ecosystem reponses to water and N inputs. Pm+Cm effectively mitigate N2O emissions by promoting complete denitrification, offering a mechanistic basis for designing afforestation strategies to synergistically support ecological restoration and N2O mitigation in semi-arid regions.

Mulching is an agronomic practice that improves orchard soil and promotes root growth. To investigate the regulatory effects of different mulching materials on soil properties, microbial communities, and root function in apple orchards, eight treatments were established: clean tillage (CK), organic fertilizer mulching (OFM), chopped corn straw mulching (SM1), chopped and bundled corn straw mulching (SM2), intact corn stover mulching (SM3), composted apple branch mulching (BM), horticultural ground cover fabric mulching (FM), and weed mulching (WM). The results showed that OFM, BM, SM1, and SM3 exhibited effective cooling effects during summer. During the peak root-flush period, OFM, SM3, and BM significantly reduced soil bulk density, increased porosity, enhanced soil organic matter and available nutrient contents, and elevated the activities of soil sucrase, urease, and catalase. Moreover, these treatments promoted the accumulation of carbohydrates and the uptake of mineral nutrients in roots. OFM and SM3 significantly increased the Simpson index of both soil bacterial and fungal communities, while BM improved the beta diversity of bacterial and fungal communities. OFM, SM3, and BM can effectively improve soil physicochemical properties, optimize microbial community structure, and enhance root nutrient uptake. It is recommended as a mulching measure for soil in northern apple orchards. Among the eight treatments evaluated, OFM, SM3, and BM exhibited superior performance in improving soil physicochemical properties, promoting root function, and enhancing microbial community diversity. Therefore, the findings of this study provide an effective soil management strategy for apple orchards in the cold northern regions of China.

The impacts of reclamation and fertilization of sandy grassland on soil microbial communities and functional groups related to carbon (C) and nitrogen (N) cycling are not well understood. To fill this gap, three types of fertilizers, namely, chemical fertilizer (CF), manure (M), and chemical fertilizer plus manure (CF_M), were applied annually for five years to reclaimed sandy cropland planted to maize. Nearby sandy grassland without fertilizer and maize was included as a control. Soil microbial communities and processes, soil properties, and aboveground biomass (AGB) were determined. Soil microbial Chao richness was lowest in soil without fertilizer and maize. Fungal Shannon diversity was lowest with chemical fertilizer plus manure, while soil microbial Chao richness and bacterial Shannon diversity were not influenced by fertilization. Reclamation and fertilization increased AGB, which was greatest with chemical fertilizer plus manure and was more than seven times greater than that of sandy grassland. Soil extracellular enzyme activities increased with chemical fertilizer plus manure. Fertilization enhanced C cycle functional groups by decreasing soil bulk density and elevating soil total N, total carbon, Firmicutes abundance, and bacterial Chao richness, but lessened N cycle functional groups by decreasing Nitrospirota abundance. Microbial functional category groups associated with C and N cycles responded differently to reclamation and fertilization of sandy soil, which, in turn, affected soil carbon sequestration and nutrient availability.IMPORTANCEReclamation and fertilization of sandy grassland altered biogeochemical functions by influencing microbial communities and functional category groups related to carbon (C) and nitrogen (N) cycling. Reclamation and fertilization could lead to the reduction of soil C content and insufficient soil N by altering functional category groups, which would be a potential risk leading to sandy grassland degradation. These findings not only improve our understanding of the consequences of sandy grassland reclamation and fertilization on ecosystem processes, but are also important for predicting soil C sequestration and nutrient cycling and for developing strategies to prevent degradation of sandy grassland.

Afforestation is a widely adopted strategy for restoring degraded dryland ecosystems; however, the temporal dynamics of belowground microbial communities and their functional implications remain insufficiently understood. We investigated soil fungal communities along a chronosequence of poplar plantations (young: 5–10 yr; mid-aged: 15–20 yr; mature: 25–40 yr) established on formerly grasslands in northern China. Fungal α diversity increased by 32

Nitrogen (N) loss poses a significant threat to global climate stability and ecosystem sustainability. Afforestation, as a key ecological restoration strategy, regulates soil N cycling processes by modulating soil microbial community structure. However, a systematic synthesis of how afforestation influences microbial-mediated N loss remains limited. To address this gap, this study conducted a bibliometric analysis using CiteSpace software, based on 104 relevant publications indexed in the Web of Science Core Collection from 1997 to 2025, to comprehensively map the knowledge structure, research hotspots, and evolutionary trajectories in the field of afforestation-driven microbial regulation of soil N loss. The results reveal three developmental phases: initiation (1997–2005), growth (2006–2020), and stabilization (2021–2025). China contributed the highest number of publications (40), while the United States exhibited the greatest academic influence; the Chinese Academy of Sciences and the Russian Academy of Sciences clusters have emerged as core research institutions. Notably, keyword and citation analyses revealed that research hotspots have shifted from process-oriented measurements, including N mineralization and N2O emissions, toward a deeper exploration of microbial community structure, biodiversity, and functional mechanisms. This study presents the bibliometric synthesis of microbial N loss mechanisms under afforestation, revealing a paradigm shift from environmental driers to microbial diversity. These insights inform microbial forest management strategies that balance N retention with carbon sequestration.

As primary drivers and modifiers of soil ecosystem processes, it remains unclear whether microbial metabolic limitation in sandy soil will affect its community structure and how microbial community responds to resource limitation. Hence, we investigated the relationship between soil microbial community and resource limitation in the Horqin Sandy land, a representative sandy ecosystem in northern China. Enzyme stoichiometric vector analysis revealed that microbial carbon (C) and nitrogen (N) limitation decreased with vegetation restoration, while phosphorus (P) limitation increased, indicating a shift from N limitation to P limitation from the semimobile dunes to semi-fixed dunes. Total N (TN) and total P (TP) were most closely associated with microbial community richness, although the influences of electrical conductivity (EC), pH and topographic factors (latitude, longitude, and elevation) were also significant. Co-occurrence network and linear mixed-effects model analyses demonstrated significant correlations (p < 0.05) between key nutrient-cycling microorganisms and C or nutrient limitation (MCL or MNL). Vegetation restoration enhanced soil carbon and nutrient levels, the abundance of keystone taxa, and microbial biomass, and. These changes subsequently altered extracellular enzyme activities, which affected the limitation of microbial resources. This pattern suggests that soil microorganisms adjust their resource acquisition strategies through low-cost metabolic investments to balance energy and nutrient constraints. Our findings provide critical insight into the response mechanisms of microbial community structure to energy and nutrient limitation in sandy ecosystems undergoing restoration.

Understanding how dominant plants respond to nitrogen（N） addition is critical for accurately predicting the potential effects of N deposition on ecosystem structure and functionality. Biomass partitioning serves as a valuable indicator for assessing plant responses to environmental changes. However, considerable uncertainty remains regarding how biomass partitioning shifts with increasing N inputs in sandy ecosystems. To address this gap, we conducted a greenhouse N fertilization experiment in April 2024, using seeds from 20 dominant plant species in the Horqin Sandy Land of China representing 5 life forms: annual grasses, annual forbs, perennial grasses, perennial forbs, and shrubs. Six levels of N addition(0.0, 3.5, 7.0, 14.0, 21.0, and 49.0 g N/（m 2 ·a）, referred to as N0, N1, N2, N3, N4, and N5, respectively) were applied to investigate the effects of N inputs on biomass partitioning. Results showed that for all 20 dominant plant species, the root biomass:shoot biomass（R:S） consistently declined across all N addition treatments（P<0.050）. Concurrently, N addition led to a 23.60% reduction in root biomass fraction, coupled with a 12.38% increase in shoot biomass fraction（P<0.050）. Allometric partitioning analysis further indicated that N addition had no significant effect on the slopes of the allometric relationships（leaf biomass versus root biomass, stem biomass versus root biomass, and shoot biomass versus root biomass）. This suggests that plants can adjust resource investment—such as allocating more resources to shoots—to optimize growth under favorable conditions without disrupting functional trade-offs between organs. Among different life forms, annual grasses, perennial grasses, and annual forbs exhibited increased allocation to aboveground biomass, enhancing productivity and potentially altering community composition and competitive hierarchies. In contrast, perennial forbs and shrubs maintained stable biomass partitioning across all N addition levels, reflecting conservative resource allocation strategies that support long-term ecosystem resilience in nutrient-poor environments. Taken together, these findings deepen our understanding of how nutrient enrichment influences biomass allocation and ecosystem dynamics across different plant life forms, offering practical implications for the management and restoration of degraded sandy ecosystems.

Land use changes impose a series of environmental pressures, which become more pronounced with restoration stages, leading to profound impacts on ecosystem functioning. However, research on the interactions within soil bacterial communities, their assembly patterns, and the associations with soil multifunctionality during forest restoration remains limited. In this study, a space-for-time substitution approach was applied to explore responses of bacterial communities during poplar forest restoration, focusing on their temporal patterns of microbial community structure, co-occurrence patterns, assembly processes, and soil multifunctionality. Our findings indicate that forest restoration significantly altered soil bacterial community composition and increased bacterial diversity (P < 0.05), notably enhancing the relative abundance of Actinobacteria and Proteobacteria. It also promoted bacterial functional groups related to carbon and nitrogen cycling, particularly those associated with nitrogen fixation (+ 174.32

Introduction:Rainfall patterns are expected to become increasingly erratic as a result of global climate change, with more intense but less frequent rainfall events leading to an increased occurrence of drought events. This process may lead to significant declines in vegetation cover and subsequent increases in soil erosion, consequently accelerating the bury of detached litter by soil deposition and the mixture of residues from different plant species. Responses of litter decomposition to increasing rainfall variability in distribution and subsequent litter mixing or soil cover have scarcely received attention. Methods:To fill this gap in our knowledge, we analyzed the influence of rainfall variability, soil cover, and litter mixing on shrub-species litter decomposition in a semi-arid shrubland. We explored the effects of redistributing the frequency and amount of precipitation on surface and belowground decomposition of litter from two separate or mixed predominant shrubs. Results:Decomposition of belowground litter was consistently higher than that of surface litter over the entire field-incubation process. Mass loss significantly decreased in surface litter but not in belowground litter due to the lower frequency and larger amount of precipitation compared to the control treatment. Furthermore, exclusion of 30% precipitation had no significant effects on decomposition of either surface or belowground litter. We observed stronger synergistic effect for belowground litter mixture relative to surface litter mixture of the two shrubs, especially in the hotter months over the 5-month incubation. Discussion:These findings support that rainfall variability in terms of distribution pattern rather than in the amount controls the litter decomposition on the soil surface in the semi-arid shrubland. Meanwhile, soil burial or litter mixing have greater effects on litter decomposition, individually or jointly. Together, our results highlight the need to consider rainfall distribution variability and incorporate soil-covering and litter-mixing as driving factors of organic matter turnover in drylands.

During the restoration of degraded ecosystems, different shrub species often segregate along environmental water gradients. However, the physiological mechanisms driving this segregation remain unclear. To address this gap, we conducted a drought stress experiment (70%-80% field water holding capacity, CK; 40%-50% field water holding capacity, MD; 20%-30% field water holding capacity, SD) to explore the physiological mechanisms driving the dominance of different shrub species at various stages of ecosystem restoration. Salix gordejevii, a species dominant in the early stages of restoration with high water availability, and Caragana microphylla, a species dominant in the later stages under low water availability, were studied. The results showed that the living state index (LSI) of S. gordejevii was significantly lower than that of C. microphylla under drought stress (P < 0.05). Differences in plant hydraulics and water-use strategies explained how these species adapt to varying soil moisture conditions. Salix gordejevii employed a proactive water-use strategy with lower water-use efficiency (WUE) and reduced resistance to xylem embolism (xylem water potentials corresponding to 50% loss of conductivity, P-50), making it better suited to environments with more abundant water. In contrast, C. microphylla adopted a conservative water-use strategy. This strategy was characterized by increased WUE and enhanced resistance to drought-induced xylem embolism, which allowed it to thrive under more drought-prone conditions. Importantly, hydraulic efficiency (K-leaf, K-s and K-1) emerged as the primary determinant of living state in both S. gordejevii (47.30%) and C. microphylla (62.20%). The lower embolism resistance of S. gordejevii (P-50 = 1.3 MPa) made it more susceptible to xylem cavitation, leading to a decline in hydraulic efficiency under SD. In contrast, C. microphylla's higher embolism resistance (P-50 = 2.3 MPa) enabled it to maintain stable hydraulic conductance across all drought treatments. These differences in hydraulic efficiency, driven by xylem embolism resistance, were key factors influencing shifts in shrub dominance during ecosystem restoration. These findings provide a physiological explanation for the replacement of shrub species during ecosystem restoration, where soil moisture is the main limiting factor.

Soil microbiome is essential for terrestrial ecosystem preservation. β-diversity information on the former, although dynamic due to its sensitivity to environmental conditions driven by climate change, is limited. Our knowledge becomes poorer for microbiomes subjected to environmental gradients, especially for those across multiple ecosystems-information important for biological conservation management. In this study, using next generation sequencing and machine learning at samples from 207 locations among 4300 km of transects that spanned among six typical terrestrial ecosystems of China, we established the divergent distance-decay relationships between bacterial and eukaryotic communities in response to soil pH (pH as proxy of climate and edaphic conditions). The findings, pH-decrease results in lower β-diversity (convergent tendency) among the bacterial communities opposite to the eukaryotic ones (low pH-high β-diversity (divergent tendency)). Meanwhile, competition between bacteria and eukaryotes intensifies at lower pH while the predominant genera and communities are re-structured. Under these circumstances, potential soil acidification due to climate change or other factors could alter soil bacteria and eukaryotes into decoupling directions influencing ecosystems' stability. Thus, soil pH is a pivotal environmental variable that not only describes, but also controls, soil microbiome dynamics at a large scale under ongoing global changes; hence, a cornerstone variable for the biodiversity conservation of China's nature protected areas and not only.

Intensive rotational grazing is a recently proposed rangeland management strategy that has been praised by the public and media but has not been fully proven or widely accepted by rangeland ecologists. In this study, a threeyear experiment was performed to evaluate the effects of intensive rotational grazing on the rangeland ecosystem in a typical steppe in Inner Mongolia, China. The experiment involved three treatments of rotational management with the same level of grazing intensity (1 sheep unit per ha in the first year and 1.3 sheep unit per ha for the next two years), including intensive rotational grazing (livestock rotated every 3-5 days), traditional rotational grazing (livestock rotated every 15 days), and continuous grazing (without livestock rotation). In addition, this experiment set up "no grazing treatment" as the reference and represents the widely used policy of "grazing forbidden". Compared with previous studies, this study first implemented rotational grazing at a low level of grazing intensity to obey the rangeland policy of Chinese governments, which aimed to balance the forage demand of livestock and the ecosystem conservation. The results revealed that the aboveground biomass and root biomass (0-10 cm deep) were significantly higher in the intensive rotational grazing treatment than in the other two grazing treatments. Moreover, the biomass of the dominant species (Leymus chinensis) and its proportion in the community were also higher in the intensive grazing treatment. Intensive rotational grazing could also promote the weight gain of grazing sheep. However, intensive rotational grazing did not improve the carbon sequestration of rangeland. These results indicated that intensive rotational grazing had considerable advantages in realizing the sustainable management of grazing grasslands when grazing intensity was at a relatively low level, which aims to balance plant growth and livestock production of grasslands. Furthermore, our results suggest that intensive rotational grazing is beneficial for promoting the progressive succession of degraded grasslands and providing economic revenue for local herders, thus worth studying in more regions and rangeland scenarios.

Afforestation drives long-term changes in soil bacterial communities, influencing soil functions and biogeochemical cycles. However, it remains unclear how these changes dependent on prior land-use history. Using a space-for-time substitution approach, we examined the impacts of poplar afforestation on the structure, diversity, co-occurrence patterns and functionality of soil bacterial communities in the agro-pastoral ecotone of northern China. Our results demonstrated that afforestation significantly enhanced bacterial α-diversity in grassland (with increasing by 7.8 %) but reduced it in cropland (decreasing by 5.9 %). Co-occurrence network analysis revealed that afforestation in grassland promoted more stable microbial interactions, increasing positive interactions from 60.6 % to 64.4 %, whereas in cropland it generated more complex but vulnerable networks dominated by negative interactions (increasing from 42.9 % to 47.5 %). Functionally, grassland conversion was associated with a substantial increase in the relative abundance of functional groups linked to nitrogen fixation potential (232.2 %) and denitrification potential (188.7 %), whereas cropland conversion was linked to a reduction in the potential of most nitrogen cycling related functions. Structural equation modeling demonstrated that afforestation-driven changes in bacterial community composition directly influenced carbon and nitrogen cycling, explaining 32 % and 60 % of functional variance in grassland and 90 % and 91 % in cropland. This study demonstrates that land-use history governs afforestation outcomes by determining the trajectory of both structural and functional responses in soil bacterial communities. We therefore emphasize that restoration strategies must be tailored to prior land-use to direct microbial processes toward sustainable ecosystem functions.

A critical issue in microbial ecology is quantifying the relative contributions of deterministic and stochastic processes to microbial community assembly, and predicting ecosystem function by understanding the ecological processes of community composition is an integral part. However, the mechanisms driving microbial community assembly along altitudinal gradients in mountain ecosystems remain largely unexplored. Here, we used high-throughput sequencing to examine the structural characteristics and diversity maintenance mechanisms of soil bacterial and fungal communities along an altitudinal gradient (2632-3661 m) in Mahan Mountain, the highest peak of the Loess Plateau. Proteobacteria, Acidobacteriota and Actinobacteriota dominated the bacterial communities, while Ascomycota, Basidiomycota and Mortierellomycota were the predominant fungal groups. Although elevation did not significantly affect bacterial and fungal alpha diversity, notable shifts in community structure were observed along the altitudinal gradients. Bacterial communities were predominantly shaped by deterministic processes, leading to pronounced structural and compositional differentiation across altitudes. In contrast, fungal community assembly was primarily determined by a combination of deterministic and stochastic processes, leading to small pronounced structural divergence. The interplay of topography, climate, and soil conditions influenced the altitudinal distribution and community structure of soil bacteria in this mountain ecosystem.

The denitrification capacity of bioretention floodplains is influenced by the downward migration of denitrifying bacteria in the soil layer during rainfall, however the mechanism of this process in response to different soil environments remains unclear. This study examined the characteristics of downward migration of functional microorganisms in soil layers with organic matter content of 1 %, 2 %, and 6 % at temperatures of 4 degrees C and 25 degrees C. The results indicated that the increased abundance of Thauera (0.06 %-25.14 %) in high-organic matter environments enhanced the leaching of microorganisms carrying denitrification genes narG and nirK (8.1 x1059.9 x107 copies g-1). When soil microorganisms live under condition of high organic matter and low temperature, their extracellular polymer (EPS) levels increased by 1.8 %-217.2 % and 17.8 %-115.3 %, respectively. Meanwhile, the changes of PN/PS in EPS under cold stress weakened the adhesion between bacteria and soil particles, further promoting the leaching of functional bacteria. Furthermore, with the increase of nitrogen loading, the leaching of microorganisms carrying narG was generally higher (6.1 x105-9.9 x106 copies g-1) than that of microorganisms carrying nirK (1.6 x105-8.6 x106 copies g-1). Low temperature inhibited the migration of nitrate-reducing bacteria, while exerting a relatively minor effect on the migration of nitritereducing bacteria. This study highlights the critical role of microorganisms migrating from the soil layer during the initial stage in establishing denitrification capacity in the lower layer of the bioretention system. It also provides valuable insights for selecting appropriate soil conditions and managing the initial stage during system construction. Additionally, it suggests a novel direction for future optimization of bioretention system performance.