Restoring natural grasslands alters the soil microbiome and biogeochemical processes, particularly carbon (C) and nitrogen (N) cycling. One of the primary ways to restore degraded grasslands is to restrict grazing for a period so that the ecosystem can recover. We examined the relationship between changes in soil microbiome composition and function with greenhouse gas emissions and soil properties during the restoration of a semiarid steppe in China. Grazing exclusion for 15 years increased CO2 and N2O emissions and CH4 uptake compared with those for 6 or 37 years. A 15- and 37-year grazing exclusion led to higher soil organic carbon levels, which correlated with increased bacterial populations and genes associated with the decomposition of carbon-rich substrates and elevated CO2 emissions. After 15 years of grazing exclusion, the abundance of methanotrophic microbes was higher, and the abundance of methanogenic microbes was lower, increasing CH4 uptake compared to continuous grazing (the control). Compared to the control (continuous grazing), 15 years of grazing exclusion resulted in elevated methanotrophic populations, depressed methanogenic populations, and consequently, enhanced CH4 uptake. Emissions of N2O increased with following increases in denitrification genes norB. Structural equation modeling revealed that grazing exclusion's effects on CO2, N2O, and CH4 fluxes were mediated by changes in plant community characteristics, soil fertility, and soil microbiomes. Further research on the microbial drivers of recovery could lead to improved management practices and ecosystem restoration and resilience.

Vegetation carbon sequestration capacity (VCSC) is essential for carbon neutrality, but systematic research on its spatiotemporal patterns and driving mechanisms across China’s moisture zones remains insufficient. Based on China’s VCSC datasets from 2001 to 2020, this study examined spatiotemporal variations and quantitatively assessed contributions of meteorological factors and human activities using the partial derivative method. The results revealed that the VCSC decreased along the moisture gradient, with the highest multiyear average in the humid zone (1,640.33 g/m2) and the lowest in the arid zone (617.04 g/m2), while its declining trend intensified substantially under high aridity stress. VCSC tended to increase across all zones, with the most pronounced increase occurring in the subarid zone (4.90 g/m2/a). The most prominent finding of this study was that human activities acted as the dominant driver of VCSC enhancement across all moisture zones, with their contribution rates decreasing along the moisture gradient from 76.20% in the subarid zone to 46.53% in the humid zone. In contrast, the driving contributions of meteorological factors displayed strong spatial heterogeneity: solar radiation had negative effects on VCSC changes in humid and subhumid regions, with contribution rates of −39.2% and −44.3%, respectively, whereas precipitation had positive effects in arid and subarid zones, with contribution rates of 23.8% and 16.6%, respectively. The innovation of this study lies in quantifying differential effects of driving factors along the moisture gradient. These findings improve understanding of the vegetation carbon cycle and support zonal ecological management and the restoration of vulnerable ecosystems.

While plastic greenhouse cultivation (PGC) significantly enhances agricultural productivity, its long-term impacts on soil ecosystems remain insufficiently understood. This study systematically investigated soils subjected to PGC for durations ranging from 0 to 20 years in Zhoukou City, Henan Province, China. These greenhouse soils were compared with adjacent open-field soils to evaluate the temporal changes in soil environmental factors, protist community dynamics, and a composite soil functional status index (CSFSI). Our results revealed that prolonged PGC was closely correlated with soil acidification, salinization, organic matter loss, and accumulation of phthalates (PAEs), with the most pronounced changes occurring within the first decade. A significant decline in soil protist α-diversity was observed with prolonged PGC (e.g., a 45.59% reduction in the Shannon index). Protist community structure shifted markedly, with Cercozoa suffering an 84.19% reduction. Furthermore, prolonged PGC was also associated with reduced complexity in protist co-occurrence networks. Statistical analyses identified PGC duration as the factor most strongly associated with explaining variations in both protist community attributes and decline in the CSFSI, with its combined effect surpassing that of any single soil property or contaminant (e.g., PAEs) in this study. Interestingly, changes in protist co-occurrence network complexity were more sensitively correlated with declines in the CSFSI than changes in taxonomic diversity alone. Collectively, these findings shed light on the potential links between prolonged PGC and soil ecosystem degradation, offering valuable insights for formulating targeted soil remediation and sustainable agricultural management strategies.

Tree nitrogen (N) economy is typically framed as a balance between root acquisition and leaf resorption, leaving root resorption largely unresolved. We propose a triadic framework - integrating root N acquisition, leaf N resorption, and root N resorption - and evaluate it in a 15-yr N addition experiment in Larix plantations, spanning young, intermediate, and mature ages. Fine roots resorbed N (mean 9.5%) but far less than leaves (72.8%). Chronic N addition reconfigured pathways with age: fine-root N resorption efficiency declined only in young stands, whereas fine-root resorption proficiency decreased consistently across all ages. Ternary analyses revealed age-dependent rebalancing, with leaf and fine-root N resorption covarying synergistically, whereas fine-root N acquisition was decoupled from leaf N resorption and shifted from a trade-off with fine-root N resorption in young trees to a synergy in mature trees. This ontogenetic switch stems from shifting N limitation and energy costs: young trees rely on a cheap self-reliant acquisition strategy under N abundance, whereas mature trees increasingly rely on mycorrhizal uptake while conserving internally as demand grows. Our findings support a triadic N economy structured by age and highlight the need for flux-based approaches that dynamically quantify pathway contributions for more accurate predictions of nutrient cycling.

IntroductionSoil management technologies centered on fertility enhancement are essential for achieving the synergistic improvement of crop yield and resource use efficiency. This study aims to identify key soil factors driving the coordinated increase in yield and nitrogen use efficiency of spring maize, thereby providing a scientific basis for promoting high yield and efficiency through improved soil quality.MethodsBased on variations in inherent soil productivity (ISP) across maize ecological regions in Inner Mongolia, China, this study established two soil management modes—Conventional Practices (CP) and Improved Soil Management Practices (IMSP)—to quantitatively identify key factors influencing ISP, yield and nitrogen use efficiency (NUE) through the random forest algorithm. The effects of soil fertility improvement on maize yield and nitrogen use efficiency were also examined.ResultsOur results showed that soil organic matter and alkali-hydrolysable nitrogen were the major nutrient related drivers of ISP, maize yield, and NUE, whereas N mineralization, N losses, soil water content, and WUE dominated process-related regulation. Among these, soil organic matter was the core factor governing ISP. Soil organic matter content indirectly affects soil nitrogen mineralization and water conservation capacity, which is the core of regulating soil productivity. The core process of synergistic regulation of maize yield and NUE by fertility improvement mainly lies in two aspects: on the one hand, by expanding the storage capacity of soil water to meet the water demand of the maize population; on the other hand, by increasing the net mineralization of soil nitrogen (16.0%), reduce the apparent loss of nitrogen (11.4%), reduce the risk of nitrogen leaching, and make it have the best soil water and nitrogen environment, so as to achieve synergy between yield and NUE. The regulation effect of IMSP model and nitrogen-dense interaction on yield increase and efficiency is more significant.DiscussionEnhancing soil fertility through increased organic matter improves water storage and net nitrogen mineralization while reducing nitrogen loss. The IMSP model and nitrogen-dense interaction effectively regulate this process, creating an optimal soil environment to synergistically achieve high maize yield and improved nitrogen use efficiency.

Soil nitrogen (N) mineralization is a key process in the cycling of N and is sensitive to ongoing human activities and climate changes. However, little is known about how grazing and N inputs separately and/or jointly affect the soil net N mineralization of grassland ecosystems across large temporal scales in the context of climate change. Here, we conducted a 4-year in situ measurement campaign of soil net N mineralization within a long-term grazing and N addition treatments in a semi-arid grassland. We found an alternating seasonal pattern of soil N transformation between mineralization and immobilization. Relative to normal year, peak N mineralization was advanced one month in the wet year, but peak N immobilization was delayed one month in the dry year. Precipitation-induced changes in soil temperature and moisture determined the seasonal dynamics of N mineralization in wet and dry years. The effects of grazing and N addition on soil N mineralization were temporally dependent. At the seasonal scale, N addition significantly accelerated soil N mineralization and immobilization in the peak growing season and the period after the peak growing season, respectively. Dry climate weakened the response of peak soil N transformation to N addition. Grazing broadly had no effect on soil N transformation during most of the experimental period, except for some events during the wet years. At the interannual scale, grazing, N addition and their interactions had no influences on cumulative net N mineralization. Further analysis showed that the interannual variation in soil N mineralization was driven by the previous year’s annual precipitation rather than the current year. Our results suggest that grazing and N addition could stabilize the soil N cycling in semi-arid grasslands over long-term time scales. Moreover, they emphasize the importance of precipitation legacy effects on soil N cycling, and thus for ecosystem productivity.

Soil erosion caused by grazing and rainfall is one of the main problems worldwide. Accurately assessing the long-term dynamics of soil erosion and exploring its drivers is essential to mitigate the risks of soil erosion. So far, there is a lack of information on the combined impacts of rainfall and grazing on soil erosion. We conducted 5-year research to monitor soil erosion during 43 rainfall events and the corresponding runoff and soil loss after winter grazing with three intensities (i.e., 2.7, 5.3, and 8.7 sheep ha−1) in a typical steppe during the growing seasons. We recorded the total runoff and soil loss, as well as vegetation traits, and soil properties at the end of growing seasons. Rainfall contributed more to vegetation in terms of species richness and biomass than grazing. Runoff and soil loss increased when rainfall increased up to 13.5 mm, after which their increase rates decreased. Grazing had more effects on soil bulk density, and soil fractions, while rainfall had more impacts on soil biocrusts. Increasing stocking rate did not alter the intensities of runoff and soil loss. A stronger vegetation root system and higher cover of biocrusts reduced runoff and soil loss, respectively. Winter grazing has little impacts on soil erosion on Chinese Loess Plateau, and it allows vegetation and soil biocrust recovery during the vegetation growing seasons, which may balance the grazing stress and soil erosion in arid and semiarid areas.

Alpine grasslands on the Tibetan Plateau constitute a pivotal component of the global carbon cycle. As the dominant CO₂ flux pathway, soil respiration demonstrates marked sensitivity to both climate warming and anthropogenic disturbances. Based on a long-term experiment combining warming (open-top chambers) and mowing (annual clipping), we systematically monitored soil respiration rates, concurrently with soil temperature and moisture, plant community traits, and soil nutrient, to elucidate the responses patterns of alpine meadow soil respiration to warming and mowing and identify their dominant drivers. Soil respiration was significantly affected by the main effects of warming and mowing (P < 0.05) and was strongly correlated with soil temperature and moisture. Q₁₀ decreased by 5.04

Grazing exclusion contributes to the restoration of degraded grassland, including its soil. Whether restoration merely affects the surface layer or also penetrates into the subsurface layer remains unclear. Therefore, taking the typical steppe and desert steppe in the Mongolian Plateau as cases, this study investigated the effects of grazing exclusion on soil microbial diversity, composition, and function in the soil surface (0-10 cm) and subsurface (10-30 cm). Bacterial diversity was higher in the surface layer than in the subsurface layer in the typical steppe, but the opposite was true in the desert steppe. Grazing exclusion significantly increased fungal diversity in the surface layer (typical steppe) or in both layers (desert steppe). Grazing exclusion significantly altered bacterial (Actinobacteria, Proteobacteria) and fungal (Basidiomycota, Ascomycota) community composition in both steppe types. In the typical steppe, both bacterial and fungal communities differed between soil layers, whereas only bacterial communities varied between soil layers in the desert steppe. Co-occurrence network stability correlated with bacterial (not fungal) community composition and was linked to soil nutrients (e.g., dissolved organic carbon, soil organic carbon, and total nitrogen) across steppe types and soil layers. Overall, our research showed that grazing exclusion showed higher proportion and stronger functioning of soil microbiome associated with plant growth promotion, nutrient acquisition, or pathogen suppression in the typical and desert steppes. The difference in microbiome between the surface layer and subsurface layer of the typical steppe depended on bacteria and fungi, while that difference only depended on bacteria for the desert steppe.

To analyze the global sensitivity of winter wheat parameters using the AquaCrop model on a global scale, the extended Fourier amplitude sensitivity test (EFAST) was utilized to identify parameter sensitivity differences in different regions and meteorological conditions represented by eight stations in Henan Province, including Zhengzhou, Anyang, Shangqiu, Luanchuan, Nanyang, Xuchang, Zhumadian, and Xinyang.The results showed that: (1) the sensitivity of crop parameters is little affected by meteorological conditions for biomass, and the sensitivity parameters of the eight regions were consistent; there were minimum growing degrees required for total biomass production (stbio), normalized water productivity (wp), maximum canopy cover in fraction soil cover (mcc), crop coefficient when the canopy was complete but prior to senescence (kcb), Growing degree-days (GDD)-from sowing to emergence (eme), and GGD-increase in canopy cover (cgc); (2) for canopy cover, the most sensitive parameters were mcc, cgc, soil surface covered by an individual seedling at 90% emergence (ccs), and other parameters were more sensitive in early growth stage of winter wheat; (3) for yield, GDD-from sowing to flowering ( flo) was the most sensitive parameter.The results of this study will provide support for the use of the AquaCrop model to investigate crop management at the local level.

Understanding livestock performance in typical steppe ecosystems is essential for optimizing grassland-livestock interactions and minimizing environmental impact. To assess the effects of different stocking rates on the growth performance, energy and nitrogen utilization, methane (CH4) emissions, and grazing behavior of Tan sheep, a 2-year grazing experiment in the typical steppe was conducted. The grazing area was divided into 9 paddocks, each 0.5 ha, with 3 spatial replicates for each stocking rate treatment (4, 8, and 13 sheep per paddock), corresponding to 2.7, 5.3, and 8.7 sheep ha(-1). The results showed that the neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents of herbage varied between grazing years (P<0.05), with a positive correlation between stocking rate and crude fiber content in the herbage (P<0.05). Dry matter intake (DMI) decreased with increasing stocking rate (P<0.05), and the average daily gain (ADG) was highest at 2.7 sheep ha(-1) (P<0.05). Compared to 2.7 and 8.7 sheep ha(-1), the 5.3 sheep ha(-1) treatment exhibited the lowest nutrient digestibility for dry matter, nitrogen, and ether extract (P<0.05). Fecal nitrogen was lowest at 8.7 sheep ha(-1) (P<0.05), while retained nitrogen as a proportion of nitrogen intake was highest. Digestive energy (DE), metabolic energy (ME), and the ratios of DE to gross energy (GE) and ME to GE were highest at 8.7 sheep ha(-1) (P<0.05). In contrast, CH4 emissions, CH4 per DMI, and CH4E as a proportion of GE were highest at 2.7 sheep ha(-1) (P<0.05). Stocking rate and grazing year did not significantly affect rumen fermentation parameters, including volatile fatty acids, acetate, propionate, and the acetate/propionate ratio. At 8.7 sheep ha(-1), daily grazing time and inter-individual distance increased, while time allocated to grazing, walking, and ruminating/resting decreased as stocking rates increased (P<0.05). This study highlights the importance of adjusting stocking rates based on the nutritional value of forage and grazing year to optimize grazing management.

Due to the sensitivity of alpine meadow ecosystems in the Qinghai-Tibet Plateau to climate change and human activities, dominant plants are gradually being replaced, potentially triggering ecosystem shifts and affecting soil organic carbon (SOC) sequestration. We conducted a three-year dominant plant removal experiment to assess impacts on SOC and related ecological attributes. The results showed a significant increase in SOC across all removal treatments, with the greatest increase following the loss of the dominant species. This increase was enhanced by changes in soil moisture and nitrogen, and was also partly attributed to the presence of remaining plant species. On the contrary, SOC accumulation was less responsive to soil moisture and nutrients under the dominant functional group or total removal, indicating that more severe disturbances reduce the supporting factors of SOC. Metal ions also positively influenced SOC following the loss of the dominant plant group. In particular, this study focused on shallow soil layers (0-10 cm), where SOC gains raise concerns about long-term stability. Correlation analyses and structural equation model revealed that, after the removal of the dominant species, the remaining species maintained the coupling between ecological attributes, preserving ecosystem functioning. However, the removal of dominant functional groups completely disrupted the connections between ecological attributes, reducing the complexity of SOC regulation and key mediating effects. Therefore, prioritizing the restoration of dominant species groups and functional groups is essential for maintaining ecosystem interactions and promoting effective recovery in meadow restoration.

Grazing can alter the physicochemical properties of soil and quickly influence the composition of microbial communities. However, the effects of grazing intensity on fungal community composition in different soil depth remain unclear. On the Inner Mongolia Plateau, we studied the effects of grazing intensity treatments including no grazing (NG), light grazing (LG), moderate grazing (MG), heavy grazing (HG), and over grazing (OG) on the physicochemical properties and fungal community composition of surface (0–20 cm) and subsurface (20–40 cm) soil layers. The α-diversity of fungi in subsurface soil decreased under the influence of grazing. The relative abundance of Ascomycota in the subsoil was higher than that in the topsoil, while the situation of Basidiomycota was the opposite. This was caused by the differences in the soil carbon (C) environment for the growth of oligotrophic and copiotrophic fungi. In the subsoil, grazing affected nutrient contents such as soil organic matter (SOM) and total nitrogen (TN), resulting in significantly lower relative abundance of Ortierellomycota under LG, HG, and OG than in the NG. HG showed much higher relative abundance of Glomeromycota. Results of a multiple regression tree (MRT) analysis revealed that TN and nitrate nitrogen affected the fungal α-diversity in top- and subsoils, respectively; the main driving factor regulating fungal community changes was soil water content (SWC) in the topsoil, while it was ammonium nitrogen and nitrate nitrogen in the subsoil. The results of our study indicate that grazing changes the soil environment by changing TN, SWC, nitrate nitrogen, ammonium nitrogen, and affects the diversity and community structure of soil fungi. This provides empirical support for coping with the impact of grazing on soil microbiomes in desert steppes.

To address the critical challenges of wind erosion mitigation and sustainable soil management in the fragile agroecosystem of the black soil region in the foothills of the Daxing’anling Mountains, this study evaluated five tillage practices—conventional ridge tillage (CP), no tillage with straw removal (NT), no tillage with straw mulching (R+NT), autumn strip tillage with straw mulching (R+STA), and spring strip tillage with straw mulching (R+STS)—across two landforms: gently sloped uplands and flat depressions. The results demonstrated that R+STS achieved superior performance across both landscapes, exhibiting a 42.99% reduction in the wind erosion rate, a 48.88% decrease in soil sediment discharge, and a 52.26% reduction in the soil creep amount compared to CP. These improvements were mechanistically linked to the enhanced surface microtopography (aerodynamic roughness increased by 1.8–2.3 fold) and optimized straw coverage (68–72%). R+STS also enhanced the topsoil fertility, increasing the total nitrogen (TN), soil organic carbon (SOC), alkaline nitrogen (AN), available phosphorus (AP), and rapidly available potassium (AK) by 22.07%, 12.94%, 14.92%, 32.94%, and 9.52%, respectively. Furthermore, it improved maize emergence and its yield by 10.04% and 9.99% compared to R+NT. Mantel tests and SEM revealed strong negative correlations between erosion and nutrients, identifying nitrogen availability as the key yield driver. R+STS offers a sustainable strategy for erosion control and productivity improvement in the black soil region.

Study region: China drylands Study focus: Frequent climatic water availability stress, high vapor pressure deficit (VPD), and low soil moisture (SM) impose significant water stress on the carbon sequestration capacity of dryland ecosystems. However, which indicator dominates the carbon sequestration capacity in China's drylands remains unclear. Here, we analyzed the changes in the carbon sequestration capacity of natural vegetation ecosystems in China's drylands over the past 40 years. Standardized precipitation evapotranspiration index (SPEI) was used to represent climatic water availability, VPD to represent atmospheric water demand, and SM to represent soil water availability. We then compared the relative effects of SPEI, VPD and SM on the carbon sequestration capacity of ecosystems. New hydrological insights for the region: Over the past 40 years, the carbon sequestration capacity of ecosystems in China's drylands has increased at a rate of 4.9 +/- 0.13 g Cm-2 per decade, while water stress has progressively intensified. Among all the water stress factors, SPEI dominates 44.04 % of the natural vegetation in China's drylands, while high VPD and low SM dominate 34.74 % and 21.22 %, respectively. However, as the aridity index (AI) increases, the relative effects of VPD and SM gradually surpass that of SPEI, with AI thresholds of 0.36 and 0.91, respectively. Our study highlights that, in the context of climate change, the decline in climatic water availability should be considered the foremost water stress constraining the carbon sequestration capacity of dryland vegetation ecosystems in China.

In saline ecosystems, halophytes reshape their phyllosphere microenvironment through unique salt-tolerance strategies, driving microbial community differentiation and functional adaptation. But under extreme conditions, a comprehensive understanding of how these microbes respond to environmental cues and subsequently influence their hosts remains elusive. Leaf physiological-biochemical traits and high-throughput amplicon sequencing data of phyllosphere microbiota from three representative halophytes—Suaeda salsa (SS), Nitraria sibirica (NS), and Salicornia europaea (SE)—were collected and analyzed along gradients of soil salinity and water content. Soil water stress, induced by the combined effects of soil salinity and moisture, is a pivotal factor driving differences in plant physiological-biochemical traits. Under the influence of these trait variations, deterministic processes jointly governed the assembly of phyllosphere bacterial and fungal communities, yet their composition, diversity, and metabolic functions exhibited marked differences. Specifically, the key bacterial genus Planococcus, fungal taxa within Ascomycota, and metabolic functions associated with antioxidant stress responses were significantly enhanced in SS; the bacterial genus Vibrio and metabolic functions linked to microbial competition-defense mechanisms and oligotrophic traits were enhanced in SE. Varying degrees of increase in key fungal and bacterial taxa across the phyllosphere of all three species further influenced community diversity, but stochastic processes also contributed to fungal community assembly. Findings reveal that soil water stress indirectly impacts phyllosphere microbial communities, with differences in the stress-tolerant physiological-biochemical traits of halophytes under varying water stress conditions significantly shaping microbial community composition. Moreover, the stress-resistance traits exhibited by phyllosphere microbiota may enhance plant adaptation to extreme environments.

Restoration of vegetation, soil, and biodiversity is key crucial for managing desertified ecosystems; however, whether desertification restoration promotes the accumulation of microbial necromass carbon (NC) remains unclear. In this study, four dune types (mobile, semi-mobile, semi-fixed, and fixed) were selected to represent different desertification restoration stages, and the accumulation mechanism of microbial NC and its contribution to soil organic carbon (SOC) were analyzed. The results showed that since the plant diversity, soil water content, and microbial activity of semi-mobile, semi-fixed, and fixed dunes were higher than those of mobile dunes, the SOC in semi-mobile (2.63 g kg- 1), semi-fixed (2.98 g kg- 1), and fixed (3.82 g kg- 1) dunes were significantly higher than that in mobile dune (0.98 g kg- 1). Moreover, sand dune fixation promoted microbial NC accumulation and increased microbial NC/SOC ratio but decreased fungal NC/bacterial NC ratio. In addition, our study showed that plant diversity is the main factor influencing microbial NC, which has direct and indirect effects on microbial NC accumulation. In conclusion, sand dune fixation enhances microbial NC accumulation and its contribution to SOC, and the change is driven mainly by plant diversity. This study enhances our understanding of the microbial NC accumulation mechanism during dune restoration.

Overgrazing and drought are critical drivers of grassland degradation, yet their combined impacts on plant growth and succession, especially the dominant species, are still poorly understood, making it difficult to develop the sustainable pasture management. We conducted a three-year field experiment (2019-2021) on China's Loess Plateau to assess the intricate impacts of grazing management (NG - no grazing, CG - cassation of grazing, and HG - grazing with high intensity) and precipitation reduction (R0 - no precipitation reduction, R30 - 30 % precipitation reduction, and R60 - 60 % precipitation reduction) on the growth and reproduction of Artemisia capillaris, a dominant species in the semi-arid grassland ecosystem. Our results show that HG significantly decreased plant height, crown width, reproductive branches, and aboveground biomass. CG only facilitated partial recovery of these traits, suggesting a prolonging grazing cassation is essential for ecosystem restoration after a long period of overgrazing. A. capillaris exhibited a preference for asexual reproduction, with potential trade-offs between sexual and asexual modes in response to varying environmental conditions. Precipitation reduction primarily affected vertical growth, with cumulative effects observed after three years (i.e., in 2021). Compared to precipitation reduction, grazing imposed a more substantial negative impact on aboveground biomass, indicating the need for optimum grazing strategies in grassland management. The findings underscore the importance of considering dominant species and highlight the long-term consequences of overgrazing that must be incorporated into sustainable grassland management practices in semi-arid regions. The study delivers insights into pasture management science, and addresses that grazing cessation may be an appropriate method of grassland management, mitigating the negative effects of prolonged overgrazing and precipitation reduction on the growth and reproduction of dominant species in semi-arid regions.

Climate and geographical changes significantly influence food availability and nutrient composition over time and space, Which in turn affects the selection of microbial communities essential for maintaining gastrointestinal homeostasis and facilitating dietary adaptation. Therefore, it is essential to understand the specific responses of the gut microbiota to dietary and seasonal variations in order to improve animal conservation strategies based on solid scientific knowledge. In summer, due to the higher nutritional quality of forage, Tan sheep exhibited enhanced forage degradation and fermentation. This was reflected by increased populations of key rumen bacteria, including Bacteroidetes, Prevotella_1, Prevotellaceae_UCG-003, Ruminococcus_1, Saccharofermentans, and Ruminococcaceae_UCG-014. Supplementation with cellulase further facilitated these processes, optimizing the utilization of available nutrients. In contrast, during winter, when the nutritional quality of forage decline, we observed lower indicators of forage degradation and fermentation in Tan sheep. Additionally, there was a significant increase in the Firmicutes/Bacteroidetes ratio, microbial diversity, microbial interactions, and metabolic activity. The rumen microbiota adapts to enhance the breakdown of forage biomass and maintain energy balance during periods of inadequate nutritional value. Supplementing the diet with cellulase during these times can help mitigate the reduced digestibility associated with low-quality forage. This study highlights the dynamic adaptation of the rumen microbiota to seasonal variations in forage quality and emphasizes the potential benefits of cellulase supplementation in supporting rumen function and improving animal performance under varying environmental conditions.

BACKGROUND:Leymus chinensis is a vital, dominant grass species in Eurasian temperate grasslands, including the Inner Mongolian steppe. L. chinensis exhibits enhanced drought tolerance through symbiosis with arbuscular mycorrhizal fungi (AMF). The physiological mechanisms behind this drought resistance need to be unraveled. A pot experiment was conducted with four inoculation treatments (inoculation with Funneliformis mosseae, with Claroideoglomus etunicatum, or with both, and no inoculation) and three drought treatments (no drought (75.00% field capacity), mild drought (56.25% field capacity), severe drought (37.50% field capacity)) to analyze how AMF enhance drought resistance of L. chinensis. RESULTS:The results showed that drought stress inhibited the growth of L. chinensis, depending on its intensity, whereas AMF inoculation significantly improved growth and alleviated the effects of drought stress. Regardless of drought conditions, AMF inoculation significantly enhanced key biochemistry parameters, including soluble sugar concentration and antioxidant enzyme activities, ultimately promoting plant productivity. Structural equation models (SEMs) further showed that the increase in biomass of L. chinensis inoculated with AMF during mild drought was primarily due to reduced catalase activity and increased cytokinin concentration by increased soluble sugar concentration. However, under severe drought, the increase in biomass of L. chinensis inoculated with AMF was associated with increased soluble sugar concentration caused by increased peroxidase activity and reduced cytokinin concentration. CONCLUSIONS:The mechanisms by which AMF enhance the drought resistance of L. chinensis vary depending on the severity of drought. AMF increase the soluble sugar concentration by enhancing photosynthetic activity to improve drought resistance under mild drought. Under severe drought conditions, AMF enhance the concentration of soluble sugars in L. chinensis by further activating the expression of antioxidant enzyme genes, thereby improving its drought resistance. Additionally, C. etunicatum maintains high ectomycelium by requiring less carbon sources to efficiently absorb the residual soil moisture under severe drought, thus superiorly enhancing the drought resistance of L. chinensis. This study provides a theoretical foundation for the application of AMF fertilizer to improve the productivity of L. chinensis in arid grasslands.