Search Results (85)

With the ongoing intensification of climate warming and human activities, the permafrost on the Qinghai–Tibet Plateau has exhibited a degradation trend characterized by rising ground temperatures and thickening active layers over the years. Particularly in ice-rich permafrost regions, thermal melting disasters, such as ground subsidence caused by thermal melting, pose a significant threat to infrastructure in permafrost areas. Based on monitoring data from the source region of the Datong River, this article developed a calculation model for active layer thickness (ALT) based on underlying surface types. Utilizing an underground ice distribution model established through geomorphic classification and lithological characteristics, in conjunction with the Nelson model, a risk evaluation of thermal melting disasters in the source region of Datong River was conducted. Based on the current warming trend, the future variation trend of ALT was predicted, and thermal stability was evaluated. The results indicated that ALT in the source region ranged from 1.0 to 3.5 m, with a close correlation between ALT and underlying surface types. The overall thermal stability of the source region is relatively satisfactory, yet it is inadequate in high-altitude areas and on bare ground. Compared to bare ground, swamp meadows and alpine meadows offer superior protective effects on the thermal stability of permafrost in the source region. Full article

A novel planctomycete, strain T20PH1^T, was isolated from alpine meadow soil collected at an altitude of 1800 m in the North Caucasus Mountains, Russia. Phylogenomic analysis placed it within the family Tepidisphaeraceae of the class Phycisphaerae. The closest relatives based on 16S rRNA gene sequence similarity are Fontivita pretiosa B-254^T (88.9%), ‘Humisphaera borealis’ M1803^T (88.6%), and Tepidisphaera mucosa 2842^T (88.4%). Strain T20PH1^T is the first soil-derived representative of the class Phycisphaerae. Cells of strain T20PH1^T are motile, pink-pigmented cocci reproducing by binary fission. This planctomycete is an obligately aerobic chemoorganotroph with growth optima at 25–30 °C and pH 6.0–7.0. A notable functional trait of strain T20PH1^T is its ability to grow on cellulose, including microcrystalline, fibrous and carboxymethyl cellulose, as well as on xylan, starch, lichenan and xanthan. The genome comprised a 5.15 Mb chromosome and a 125 kb plasmid with G + C contents of 65.97 and 66.75%, respectively. Genome analysis identified a GH5_5 subfamily cellulase as the most likely enzyme responsible for cellulose degradation by this planctomycete. Based on phenotypic and phylogenomic evidence, strain T20PH1^T (=LMG 34157^T = KCTC 102499^T) was classified as representing a novel genus and species, Terrisphaera alpina gen. nov., sp. nov. Full article

High-density rodent populations cause severe habitat degradation and ecological imbalance in natural grasslands through intense foraging and burrowing activities. However, dynamically monitoring these small mammals and assessing their large-scale damage using traditional ground surveys alone is challenging. In this study, we evaluated rodent damage severity in alpine meadows and typical steppe by proposing an integrated framework that combines ground, unmanned aerial vehicle (UAV), and satellite data. Using data from 36 plots per grassland type, we extracted a suite of ecological parameters, including aboveground biomass, vegetation cover, community height, rodent burrow density, and plant diversity metrics, to construct a plot-scale Rodent Damage Index ($RDI$). This $RDI$ was then linked with a satellite-derived Remote Sensing Ecological Index ($RSEI$) to model and map damage severity at the regional scale. Separate linear regression models were developed for the two grassland types. The alpine meadow model exhibited better model fit and predictive performance (fitting $R^2$ = 0.762, RMSE = 0.136; LOOCV $R^2$ = 0.729, RMSE = 0.145, 95% CI: 0.580–0.886) than the typical steppe model (fitting $R^2$ = 0.574, RMSE = 0.198; LOOCV $R^2$ = 0.478, RMSE = 0.214, 95% CI: 0.279–0.787), highlighting that the predictive relationship model performance differs significantly between grassland types. Our findings demonstrate that integrating multi-source, cross-scale spatial data is an effective approach for assessing rodent damage. Furthermore, these results indicate that rodent damage assessment should be grassland-type-specific to ensure accuracy and support targeted rodent damage management planning. Full article

Climate warming is accelerating permafrost degradation in alpine regions, promoting the development of thaw-related slope deformation through active-layer thickening, ground-ice thaw, and hydro-mechanical weakening. Permafrost degradation margins are particularly sensitive to climatic warming, where enhanced heat transfer and active-layer water migration can accelerate shallow slope instability; however, the underlying mechanisms require further investigation. This study investigates two representative freeze–thaw-related landslides in the western Qilian Mountains: an active-layer detachment developed in degraded discontinuous permafrost and a freeze–thaw-induced shallow creep landslide located near the lower limit of permafrost occurrence. UAV photogrammetry, electrical resistivity tomography, and SBAS InSAR were integrated to characterize geomorphic features, internal frozen ground conditions, and deformation patterns. The active-layer detachment shows strong subsurface heterogeneity, with residual high-resistivity frozen bodies separated by localized thawed zones. Its deformation is mainly concentrated in the upslope detachment zone and central depletion–transport zone, where meadow-mat cracking, turf stripping, and exposed mineral soil coincide with thawed corridors between discontinuous permafrost bodies. In contrast, the freeze–thaw-induced shallow creep landslide exhibits the largest deformation in the upper permafrost-margin sector, where weakly discontinuous permafrost persists, whereas deformation decreases downslope in the seasonally frozen ground sector. This study highlights the critical role of discontinuous permafrost, localized thawing, and active-layer water migration in promoting shallow slope deformation and suggests that permafrost degradation margins may become increasingly susceptible to freeze–thaw-induced landslide activity under continued climate warming. Full article

Although bud banks are key components of vegetation regeneration in degraded alpine meadows, their relationships with soil conditions on the Qinghai–Tibet Plateau remain insufficiently understood. In this study, we investigated bud bank composition and density, plant functional group biomass, soil physicochemical properties, and soil microbial biomass across five degradation stages of alpine meadows in a long-term controlled grazing experiment. Field sampling was conducted in mid-August 2021, and the relationships between bud bank densities, plant biomass, and soil variables were evaluated using comparative statistical analyses, redundancy analysis, and structural equation modeling. Bud bank density increased from non-degraded to moderately degraded meadows, reaching 3075 buds m⁻², but declined sharply in severely degraded meadows to 183 buds m⁻². Regarding distinct bud types, rhizome and tiller bud densities peaked in moderately degraded alpine meadows (1217 and 1750 buds m⁻², respectively), whereas dicot bud density peaked in lightly degraded meadows. Bud bank density was positively associated with higher soil moisture content and negatively associated with increased soil bulk density. Moreover, bud bank density was positively correlated with soil organic carbon, total phosphorus, ammonium nitrogen, and soil microbial biomass carbon, nitrogen, and phosphorus. Our findings indicate that soil conditions may favor the maintenance of high bud bank density in moderately degraded meadows with high soil moisture, low bulk density, and more nutrient-rich soil conditions in moderately degraded meadows. Overall, our results indicate that alpine meadow degradation influences belowground regenerative capacity through changes in soil conditions and associated shifts in bud bank dynamics. Therefore, assessments and restoration of degraded alpine meadows should consider bud bank persistence in addition to aboveground vegetation characteristics. Full article

Although grazing is a key driver of nitrogen cycling in alpine meadow soils, a systematic understanding of how different grazing intensities shape the structure and functional potential of soil nitrogen-cycling microbial communities remains lacking. In this study, soil samples were collected under five grazing intensities (no grazing, light grazing, moderate grazing, heavy grazing, and extreme grazing) and metagenomic sequencing was employed to analyze variations in nitrogen-cycling microbial communities and functional genes. The results showed that bacteria were the dominant group in nitrogen-cycling communities (relative abundance: 93.99–98.98%), with significant community differentiation across grazing intensities. Light grazing maintained relatively high microbial diversity, whereas moderate and heavy grazing led to more pronounced differences in community composition. Functional gene analysis identified 41 nitrogen-cycling-related genes, primarily involved in denitrification, nitrate reduction, and ammonia assimilation. Light grazing enhanced nitrate reduction and glutamate synthesis; moderate grazing exhibited the strongest ammonia assimilation potential; heavy grazing significantly increased denitrification activity, indicating an elevated risk of nitrogen loss; and under extreme grazing, both the number and abundance of nitrogen-cycling functional genes declined markedly, with functional composition becoming simplified. Collectively, light grazing is more conducive to maintaining the balance between soil microbial diversity and nitrogen-cycling function in alpine meadows, whereas overgrazing disrupts the equilibrium between microbial communities and nitrogen metabolism. This study provides a microbiological basis for the restoration of degraded alpine meadows and sustainable grazing management. Full article

The Source Region of the Yangtze River is a high-altitude area with extensive permafrost on the Tibetan Plateau. While temperature, precipitation, and radiation significantly affect vegetation phenology, the influence of permafrost changes remains unclear. Using the daily Long-term Seamless NOAA AVHRR NDVI Dataset of China (2003–2022), we extracted the start (SOS) and end (EOS) of the growing season in the Source Region of the Yangtze River (SRYR). Soil thawing date (SOT) was obtained from freeze–thaw state products, while active layer thickness (ALT) was estimated using the Stefan model based on MODIS land surface temperature (LST). Partial least squares regression and mediation analysis quantified the direct and indirect effects of permafrost degradation. Results show: (1) The end of the growing season (EOS) became significantly earlier in 64.33% of the region, while the start of the growing season (SOS) showed little change. (2) The effect of SOT on SOS depends on moisture conditions. Earlier SOT leads to earlier SOS in wetter areas by supplying meltwater, but delays SOS in cold–dry areas by increasing soil water loss. (3) Thicker ALT strongly promotes earlier EOS, accounting for up to 42.61% of EOS variation in cold–dry zones, because a deeper active layer potentially promotes downward movement of water, which may further lead to the potential leaching of nutrients from the shallow root zone, limiting resources for shallow-rooted plants. (4) Alpine meadows respond more strongly to permafrost changes than alpine grasslands. Overall, water loss caused by permafrost degradation may reduce the potential lengthening of the growing season under climate warming, highlighting the key role of soil water in linking permafrost and vegetation dynamics. Full article

Alpine meadow degradation is a serious challenge for animal husbandry and ecosystem safety in the Qilian Mountain area, northwest China. Although some restoration methods have been used, fertilization practices still rely heavily on chemical fertilizers. As a type of green and effective fertilizer, microbial fertilizer was put into a degraded alpine meadow in this study, and six fertilization treatments, including no fertilization (CK), diammonium phosphate (600 kg∙ha⁻¹) (DP), microbial fertilizer (75 kg·ha⁻¹) (MF), diammonium phosphate (600 kg∙ha⁻¹) with microbial fertilizer (75 kg·ha⁻¹) (DPMF1), diammonium phosphate (450 kg∙ha⁻¹) with microbial fertilizer (75 kg·ha⁻¹) (DPMF2), and diammonium phosphate (300 kg∙ha⁻¹) with microbial fertilizer (75 kg·ha⁻¹) (DPMF3), were conducted on a moderately degraded alpine meadow using field plot experimental methods to evaluate the effects of reduced chemical fertilizer combined with microbial fertilizer on the vegetation and soil characteristics of degraded alpine meadow in 2023 and 2024. The results indicated that DP showed the highest biomass production in the two study years, but there was no significant difference between DPMF2 and DP in 2024. The dominance of originally fine forage Kobresia humilis and Medicago ruthenica showed the highest values for the DPMF3 treatment in 2023 and for the DPMF2 treatment in 2024. The vegetation Shannon–Wiener diversity and richness indices of DPMF1, DPMF2 and DPMF3 were significantly higher than those of CK. However, community diversity decreased in the second year of fertilization. DPMF2 treatment significantly increased the contents of soil organic matter, available nitrogen and available phosphorus in 2024. Grey correlation analysis indicated that 450 kg·ha⁻¹ of diammonium phosphate combined with 75 kg·ha⁻¹ of microbial fertilizer was the most suitable regime for moderately degraded alpine meadow restoration in the study area. Full article

The Qilian Mountains serve as a crucial ecological security barrier in western China, and the soil structural stability of alpine meadows directly affects regional ecological security and the sustainable utilization of grasslands. However, current research on grazing mostly relies on short-term artificially controlled experiments, which differ greatly from the pattern of long-term natural grazing. Herein, this study abandoned the artificially controlled grazing method and selected sampling areas with stable grazing regimes for more than a decade. Taking no grazing (CK) as the control, four treatments were established, including light grazing (LG), moderate grazing (MG), heavy grazing (HG) and extreme grazing (EG). The particle size distribution and stability of mechanically stable and water-stable soil aggregates in different soil layers were determined. Combined with environmental and biological factors, the effects of grazing on the structure and stability of soil aggregates were elucidated. The results showed that no grazing improved the mechanical stability of soil aggregates but reduced their water stability. Light and moderate grazing maintained a balanced and resistant soil structure, with the surface soil being more fragile than the subsurface soil. Heavy and extreme grazing led to severe structural degradation, with the subsurface soil being more fragile than the surface soil. Soil aggregate stability was jointly regulated by elevation, soil properties, root biomass, nitrogen forms, mineralization and microbial biomass. In conclusion, from the perspective of soil structural stability and sustainable utilization, light and moderate grazing represent the optimal utilization mode for the alpine meadows of the Qilian Mountains. This mode not only maintains the structural stability of subsurface soil aggregates but also balances biological cementation and physical disturbance, thus avoiding the insufficient water stability under no grazing and the risk of structural fragmentation under heavy or extreme grazing. Environmental and biological factors mediated the divergent responses of mechanical and water stability to different grazing intensities. The findings of this study provide a scientific basis and new insights for the rational grazing management and soil conservation of alpine meadows in the Qilian Mountains. Full article

The alpine meadows on the Qinghai-Tibetan Plateau function as critical reservoirs for regional water resources, yet face severe degradation driven by climate warming and overgrazing. Although establishing Poa pratensis artificial grasslands is a common restoration strategy, their effectiveness in recovering hydrological functions along restoration chronosequence remains poorly quantified. This study evaluated the changes in water conservation capacity and its drivers across a degradation–restoration sequence in the Qilian Mountains comprising alpine meadow (AM), degraded meadow (DM), and 2-, 3-, and 13-year artificial grasslands (AG2, AG3, AG13). Vegetation characteristics, soil structural properties, and water-holding indices were measured to assess restoration outcomes. The results showed that compared to AM, water-holding capacity at 0–30 cm in DM declined by 75.3–85.8%, primarily due to fragmentation of the mattic epipedon and deterioration of soil aggregates. While artificial restoration improved vegetation traits and some soil properties, hydrological recovery exhibited a distinct lag. Specifically, soil water-holding capacity in artificial grasslands showed no statistically significant improvement compared to DM. Even in AG13, soil water storage remained significantly lower than that in AM. Mantel tests and regression analyses identified root mass density and mean weight diameter as the primary drivers governing water conservation capacity. These findings reveal that artificial grasslands cannot serve as functional hydrological reservoirs in a timely manner, highlighting the importance of conserving intact alpine ecosystems. Full article

Monoculture and mixed sowing are common practices for restoring degraded alpine meadow grasslands. To investigate the effects of different sowing patterns on soil bacterial community characteristics in alpine artificial grasslands, this study examined a 20-year-old established artificial grassland, systematically analyzing plant community attributes, soil physicochemical properties, and the diversity and functional structure of soil bacterial communities under various monoculture and mixed-sowing treatments. The results showed that: (1) Mixed-sowing treatments significantly improved soil physicochemical properties and plant community characteristics. The P4 (Elymus nutans + Poa pratensis + Festuca sinensis + Poa crymophila) mixed-sowing treatment notably enhanced vegetation performance and soil conditions. Compared with the monoculture P1 (Elymus nutans) treatment, aboveground biomass (AGB) and soil organic matter (SOM) content increased by 57.23% and 68.25%, respectively, indicating that perennial grass mixtures improve soil water and nutrient retention, thereby promoting plant growth. (2) Microbiome analysis revealed that mixed sowing significantly optimized the structure of rhizosphere bacterial communities. Operational Taxonomic Units (OTUs), which represent sequence-based taxonomic units and their abundance information, were most abundant in the P4 mixed-sowing treatment, reaching a total of 5685 OTUs. In terms of bacterial diversity indices, the OTU richness, Ace index, and Chao1 index in the P4 mixed-sowing treatment were 26.12%, 25.81%, and 24.34% higher, respectively, than those in the monoculture P1 treatment, with all differences being statistically significant (p < 0.05). (3) Mantel test and redundancy analysis (RDA) revealed that soil electrical conductivity (SEC) and pH were negatively correlated with bacterial diversity indices, while soil organic matter (SOM) was identified as the key environmental driver shaping bacterial community assembly. In summary, appropriate grass mixtures effectively enhance “plant–soil–microbe” interactions, leading to improved soil fertility and optimized bacterial communities, representing a viable strategy for long-term ecological restoration and sustainability of alpine artificial grassland ecosystems. The P4 treatment—comprising a four-species mixture of Elymus nutans, Poa pratensis, Poa crymophila, and Festuca sinensis—achieved the best overall performance. Full article

As a major water conservation region and ecological security barrier in China, the Three-River Source Region (TRSR) of the Qinghai–Tibet Plateau (QTP) is underlain by extensive permafrost. However, how permafrost degradation alters regional water conservation, particularly the existence of critical thresholds and time-lagged responses, remains insufficiently understood. To clarify these issues, spatiotemporal variations in water conservation (1990–2020) were quantified, and their nonlinear, lagged, and spatially heterogeneous responses to active layer thickness (ALT) were assessed. Using multi-source remote sensing and in situ observations from 1990 to 2020, spatiotemporal variations in water conservation were quantified with the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model, and responses to permafrost degradation were examined by integrating Sen’s slope, GeoDetector, geographically weighted regression (GWR), and structural equation modeling (SEM) methods. The results showed that water conservation increased overall during 1990–2020 and exhibited a pronounced southeast–northwest gradient (higher in the southeast and lower in the northwest); the rates of change in the Lancang, Yellow, and Yangtze headwaters were 63.5, 56.5, and 31.0 mm a⁻¹, respectively. GeoDetector results indicate that precipitation was the dominant control on the spatial heterogeneity of water conservation (q = 0.704), and its interaction with active layer thickness (ALT) further increased explanatory power (q = 0.736). ALT also interacted with vegetation (q = 0.224) and topography (q = 0.157), suggesting that permafrost effects are modulated by vegetation condition and topographic setting in addition to water inputs. Piecewise regression identified a potential threshold at ALT = 1.77 m, indicating a shift in the ALT–water conservation relationship across this threshold. A 5–7-year lag in the response of water conservation to ALT was also detected, particularly apparent in continuous permafrost zones. Overall, water conservation exhibits a clear southeast–northwest gradient and a delayed response to ALT changes. In addition, the response exhibits clear spatial clustering, with the strongest sensitivity observed in areas with ice-rich permafrost overlain by alpine meadow, and a potential ALT breakpoint further suggests nonlinear permafrost–water conservation coupling. Full article

The degradation of alpine meadows on the Qinghai–Tibet Plateau has seriously affected the structure and productivity of grassland communities. In this experiment, a sample area was set up in Keqihetan of Zexiong Village, Youganning Town, Henan County, Mongolian Autonomous Prefecture. The degraded alpine meadow was divided into three plaque types, bare patches (BP), short-term recovered patches (SRP), and long-term recovered patches (LRP), and Native alpine meadows (NM) as controls, in order to reveal the effects of grassland degradation on community structure and aboveground/belowground biomass allocation in alpine meadow. Here, we measured total biomass (TCB), aboveground biomass (AGB), belowground biomass (BGB), and root/shoot ratio (R/S) of alpine meadows on the Qinghai–Tibetan Plateau and investigated plant community cover and height. The results showed that with the restoration of the patchy alpine meadow, the height decreased first and then increased, the amount of AGB increased first and then decreased, while the coverage and BGB increased in turn, and BGB decreased with the deepening of soil depth. We also found that R/S decreased first and then increased with the patch recovery of the alpine meadow. The overall distribution of AGB and BGB belongs to allometric growth distribution, but the native meadow belongs to isometric growth distribution, while other recovery stages belong to allometric growth distribution. By studying the biomass and its distribution of degraded grassland, we can understand the impact of grassland degradation on the community structure and productivity of the alpine meadow. Full article

Microbial communities associated with animal cadaver decomposition play a crucial role in biogeochemical cycles in both aquatic and terrestrial ecosystems. However, it remains unclear regarding the diversity, succession, and assembly of phosphate-solubilizing microbes during animal cadaver decay. In this study, plateau pikas (Ochotona curzoniae) as mammal degradation models were placed on alpine meadow soils to study diversity, succession and assembly of phosphate-solubilizing microbes using amplicon sequencing of phoC- and phoD-genes during 94 days of incubation. The total phosphorus concentration in the corpse group increased by 8.53% on average. Alpha diversity of both phoC- and phoD-harboring microbes decreased in the experimental group compared to the control group, and the community structure differed between control and experimental groups. Phosphate-solubilizing microbial community turnover time rate (TDR) of the experimental group was higher than that of the control group, indicating corpse decay accelerates the succession of phoC- and phoD-harboring microbial community. Null model revealed that deterministic process dominated phoC microbial community in corpse group, while the stochastic process dominated phoD microbial community. The microbial network in experimental group was more complicated than that in control group of phoC microbial community, while phoD microbial community showed opposite trend. Partial least squares path modeling (PLS-PM) showed that phoC-harboring microbial community was mainly influenced by pH, Total carbon (TC) and Total phosphorus (TP), while the phoD microbial community was only regulated by TP. These findings elucidate the ecological mechanism of phosphorus-solubilizing microbial community changes during animal corpse degradation. Full article

Vegetation degradation in the alpine meadows is becoming increasingly severe under global change, with species loss frequently linked to changes in plant functional groups (PFGs). Changes in PFGs alter plant-derived carbon inputs, which significantly influence soil organic carbon (SOC) sequestration and soil communities. However, the impact of specific PFG removal on soil carbon fractions and nematode trophic groups remains underexplored. In this study, above-ground removal of PFGs was carried out for five consecutive years in the Qinghai–Tibet Plateau alpine meadow, with five treatments: (1) no removal of PFGs (CK); (2) keep non-legume forbs (remove graminoids and legumes, Forbs); (3) keep graminoids (remove legumes and non-legume forbs, Graminoids); (4) keep legumes (remove non-legume forbs and graminoids, Legumes); (5) remove all PFGs (All-plants-removed). Root properties, nematode community, and soil carbon fractions were measured. We found that the Graminoids treatment significantly increased root biomass, whereas the All-plants-removed treatment led to a significant decrease. Nematode abundance was highest under the Legumes treatment, primarily due to increased omnivores-predators. Meanwhile, the soil particulate organic carbon (POC) varied significantly between PFG types, being the highest in the Forbs and CK treatments. Correlation analysis revealed a significant positive relationship between SOC and bacterivore abundance, suggesting that higher SOC enhances bacterivore populations and subsequently influences carbon cycling. We conclude that PFG removal alters soil nematode community structure and POC, underscoring the role of PFGs in below-ground biodiversity and soil carbon sequestration. Full article