Search Results (102)

Vegetation phenology serves as a crucial indicator reflecting vegetation responses to the growth environment and climate change. Existing studies have demonstrated that in permafrost regions, the impact of frozen soil changes on vegetation phenology is more direct and pronounced compared to climate factors. Amid the slowdown of global warming in the 21st century, permafrost dynamics continued to drive uncertain variations in vegetation phenological stages across the Qinghai–Tibet Plateau (QTP). Using MODIS Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) data during 2001–2024, this study derived vegetation phenological parameters and analyzed their spatiotemporal patterns on the QTP. The results indicate that overall, the start of growing season (SOS) was advanced, the end of growing season (EOS) was delayed, and the length of growing season (LOG) was extended throughout the study period. Additionally, divergent phenological trends were observed across three distinct phases, and regarding frozen soil types, vegetation phenology in permafrost and seasonally frozen ground regions exhibited distinct characteristics. From 2001 to 2024, both permafrost and seasonally frozen ground regions showed an advanced SOS and prolonged LOG, but significant differences were observed in EOS dynamics. For vegetation types, alpine meadow displayed advanced SOS and EOS, alongside an extended LOG. The alpine steppe exhibited advanced SOS and delayed EOS with an extended LOG. Alpine desert displayed SOS advancement and EOS delay, alongside LOG extension. These findings revealed variations in vegetation phenological changes under different frozen soil types and highlighted divergent responses of distinct frozen soil types to climate change. They suggested that the influence of frozen soil types should be considered when investigating vegetation phenological dynamics at the regional scale. Full article

Increased Nitrogen (N) input exerts significant impact on the functional integrity of terrestrial ecosystems, with alpine grasslands being particularly susceptible. Soil microbes are intricately intertwined with nearly all facets of essential biogeochemical cycle, underscoring their pivotal role in ecosystem processes. To elucidate how N enrichment modulates soil microbes and their diversity, 11-year N addition experiments were conducted in a semi-humid alpine meadow (AM) and an arid alpine steppe (AS) on the Northern Tibetan Plateau. We measured soil properties, aboveground net primary productivity (ANPP), plant diversity, microbial composition and diversity, as well as microbial co-occurrence networks. The results revealed that N additions profoundly reshaped microbial co-occurrence in alpine grasslands, albeit via divergent mechanisms in different ecosystems. In AM, N enrichment destabilized microbial networks mainly through reduced bacterial diversity linked to plant diversity loss. Conversely, in the harsher AS, N addition fostered closer microbial interactions, forming a more stable co-occurrence network despite lower plant richness, predominantly attributed to increased soil nutrient availability. Our results highlight the significance of co-occurrence networks as a key component of microbial biodiversity and emphasize the imperative of deciphering microbial interaction mechanisms to unravel soil functional dynamics under global nitrogen enrichment. Full article

The ecological restoration of degraded alpine steppe is a critical component of ecological conservation efforts on the Qinghai–Tibetan Plateau. In this study, we investigated the effects of fertilization, reseeding, and combined fertilization with reseeding restoration measures on the vegetation community, soil properties and microbial community diversity in degraded alpine steppe through field vegetation surveys, and soil microbial high-throughput sequencing at an experimental site of fertilized and reseeded grassland restoration located in the Yellow River Source area. The results demonstrated the following: (1) both reseeding and combined fertilization with reseeding restoration measures significantly affected grassland vegetation community structure and diversity; (2) fertilization and combined fertilization with reseeding restoration measures significantly affected soil pH and total phosphorus (TP) content; (3) while fertilization and combined fertilization with reseeding restoration measures markedly altered microbial community structure, reseeding alone significantly affected microbial diversity. Co-occurrence network analysis revealed that soil microbial communities were significantly influenced by fertilization restoration measures; redundancy analysis (RDA) showed that microbial communities under fertilization and combined fertilization with reseeding restoration measures were primarily governed by soil TP, whereas those in control and reseeding plots were strongly associated with soil pH and organic carbon (SOC). This study explored effective restoration measures suitable for degenerating alpine steppe in the Yellow River Source area, aiming to provide a scientific basis and technical support for the ecological protection and restoration of the Three-River Headwaters. Full article

Seed size and number are two important components of plant reproductive traits. Previous theoretical studies have suggested that resource limitations lead to a strong trade-off between seed size and seed number. However, empirical evidence from natural communities remains scarce. In this study, the relationship between seed size and seed number was tested at the community level and in three functional groups—graminoids, forbs, and legumes—in a natural alpine steppe community in the Tianshan Mountains. The role of limiting resources in reproduction and in determining trade-off patterns was also examined by treating the reproductive biomass and allocation of each species as a resource pool for producing seeds. Our results showed a significant negative relationship between seed size and seed number at the community level, which indicated that a trade-off between seed size and number existed and that the species that produced large seeds produced fewer seeds and vice versa. This trade-off was detected for the graminoid group but not for the forb or legume group, so the trade-off at the community level was determined primarily by graminoid species. Moreover, the graminoid group had lower reproductive biomass and allocation than the forb and legume groups, indicating that the graminoid species were more strictly limited by reproductive resources. Our study provides evidence of a seed size-number trade-off in a natural alpine steppe community, especially among graminoid species, and the important role of reproductive resources in determining the trade-off. Full article

Grassland ecosystems in arid regions increasingly experience resilience loss due to intensifying climatic variability. However, the limited interpretability of conventional machine learning models constrains our understanding of underlying ecological drivers. This study constructs an integrative framework that combines temporal autocorrelation (TAC) metrics with explainable machine learning, employing Random Forest and SHAP (SHapley Additive exPlanations) analysis. Time series of satellite-derived vegetation indices from MODIS (2001–2023), particularly the kernel Normalized Difference Vegetation Index (KNDVI), support the generation of TAC and its trend-based derivative δTAC. The framework assesses ecosystem resilience across seven representative grassland types in Xinjiang, capturing diverse responses to climate variability and vegetation dynamics. Results reveal pronounced spatial heterogeneity: resilience declines in radiation-stressed arid zones, while hydrothermally stable regions maintain stronger recovery capacity. Key drivers include temperature variability and vegetation dynamics, with divergent effects among grassland types. Meadow and Typical Steppe exhibit higher resilience under stable hydrothermal regimes, whereas desert and alpine systems show greater sensitivity to warming and climatic fluctuations. This framework enhances diagnostic transparency and ecological insight, offering a spatially explicit, data-driven tool for resilience monitoring. The findings support the formulation of targeted adaptation strategies and sustainable grassland management in response to ongoing climate change. Full article

Alpine steppe (AS), alpine meadow (AM), and alpine swamp meadow (ASM) are the principal grassland types on the Tibetan Plateau, which not only contribute to the maintenance of local ecosystem functions but also play a crucial role in global ecological processes. Soil microbial communities act as indispensable linchpins in modulating ecosystem functions. However, there is still a lack of general understanding about the regulatory mechanisms of soil fungi and bacteria with their multidimensional attributes on ecosystem multifunctionality (EMF) in different grassland types. Here, we comprehensively investigated the relative impacts of microbial diversity, community composition, network complexity, as well as the soil environmental factors on EMF in the three grassland types. Our results indicated that EMF was positively regulated by soil bacterial community composition, particularly the phyla Proteobacteriota and Verrucomicrobiota in AS. Additionally, both fungal diversity and network complexity exhibited significant positive correlations with EMF, with fungal network complexity identified as the primary driver of EMF in AM. Notably, the EMF in ASM was predominantly affected by soil moisture, rather than soil microbial community attributes. This study provides comprehensive evidence on the regulatory mechanisms of soil microbial and environmental factors in the EMF of different grassland types. These findings have significant implications for maintaining the ecosystem multifunctionality of specific grassland types. Full article

The Qinghai–Tibet Plateau is a key region for biodiversity conservation, where alpine grasslands are ecologically important. While previous studies have mainly addressed vegetation, ecosystem processes, and soil microbes, phyllosphere microorganisms are essential for nutrient cycling, plant health, and stress tolerance. However, their communities remain poorly understood compared to those in soil. The relative influence of host identity and environmental conditions on shaping phyllosphere microbial diversity and community assembly remains uncertain. In this study, we characterized phyllosphere bacterial and fungal communities of the phyllosphere at two alpine steppe sites with similar vegetation but climatic conditions: the Qilian Mountains (QLM) and the Qinghai Lake region (LQS). At both sites, Cyanobacteriota and Ascomycota were the predominant bacterial and fungal taxa, respectively. Microbial α-diversity did not differ significantly between the two regions, implying that host-associated mechanisms may stabilize within-site diversity. In contrast, β-diversity exhibited clear spatial differentiation. In QLM, bacterial β-diversity was significantly correlated with mean annual precipitation, while fungal α- and β-diversity were associated with soil nutrient levels (including nitrate, ammonium, available potassium, and phosphorus) and vegetation coverage. At LQS, the β-diversity of both bacterial and fungal communities was strongly influenced by soil electrical conductivity, and fungal communities were further shaped by vegetation cover. Community assembly processes were predominantly stochastic at both sites, although deterministic patterns were more pronounced in QLM. Variability in moisture availability contributed to random bacterial assembly at LQS, while increased environmental heterogeneity promoted deterministic assembly in fungal communities. The elevated diversity of microbes and plants in QLM also reinforced deterministic processes. Overall, our findings support a host–environment interaction hypothesis, indicating that host factors primarily govern α-diversity, while climatic and soil-related variables have stronger effects on β-diversity and microbial assembly dynamics. These insights advance our understanding of how phyllosphere microbial communities may respond to environmental change in alpine ecosystems. Full article

Despite substantial research on how environmental factors affect fungal diversity, the mechanisms shaping regional-scale diversity patterns remain poorly understood. This study employed ITS high-throughput sequencing to evaluate soil fungal diversity, community composition, and co-occurrence networks across alpine meadows, desert steppes, and alpine shrublands in the southwestern Tibetan Plateau. We found significantly higher fungal α-diversity in alpine meadows and desert steppes than in alpine shrublands. Random forest and CAP analyses identified the mean annual temperature (MAT) and normalized difference vegetation index (NDVI) as major ecological drivers. Mantel tests revealed that soil physicochemical properties explained more variation than climate, indicating an indirect climatic influence via soil characteristics. Distance–decay relationships suggested that environmental heterogeneity and species interactions drive community isolation. Structural equation modeling confirmed that the MAT and NDVI regulate soil pH and carbon/nitrogen availability, thereby influencing fungal richness. The highly modular fungal co-occurrence network depended on key nodes for connectivity. Vegetation coverage correlated positively with network structure, while soil pH strongly affected network stability. Spatial heterogeneity constrained stability and diversity through resource distribution and niche segregation, whereas stable networks concentrated resources among dominant species. These findings enhance our understanding of fungal assemblage processes at a regional scale, providing a scientific basis for the management of soil fungal resources in plateau ecosystems. Full article

The genus Dracocephalum (family Lamiaceae) comprises approximately 70 species, many of which have been traditionally used in various ethnomedical systems. The plants exhibit a broad distribution across steppe, semi-deserts, deserts, and alpine zones of temperate Eurasia, with isolated endemic species occurring in North America and North Africa. The traditional medicinal uses of the Dracocephalum species encompass the treatment of respiratory diseases, colds and fever, gastrointestinal disorders, liver and gallbladder ailments, musculoskeletal conditions, cardiovascular diseases, diabetes, gynecological and urological disorders, as well as ailments of the ears, throat, mouth, and eyes, as well as various dermatological conditions. The plants are rich sources of polyphenolic compounds, including flavonoids and phenolic acids, which contribute to their diverse pharmacological activities. The flavonoid profile of the Dracocephalum species is dominated by luteolin and apigenin derivatives, supplemented by mono-, di-, tri-, tetra-, and pentamethoxylated flavones. The predominant phenolic acids are chlorogenic acid, coumaric acid, rosmarinic acid, and their derivatives. Other phenolic compounds have also been identified in the genus: anthocyanins, lignans, phenylethanoids, phenylacetamide glycosides, flavonoid alkaloids, gingerols, coumarins, furanocoumarins, and cyanogenic glucosides. Despite growing scientific interest in this genus, a comprehensive review of its polyphenolic constituents, their structures, and associated biological activities remains lacking. To bridge this gap, this review presents an analysis of the polyphenolic profile of the Dracocephalum species, their ethnomedicinal uses, and the latest findings on their biological potential. Full article

Mountain grassland ecosystems around the globe are highly sensitive to seasonal extreme climate events, which thus highlights the critical importance of understanding how such events have affected vegetation dynamics over recent decades. However, research on the time-lag of the effects of seasonal extreme climate events on vegetation has been sparse. This study focuses on Tajikistan, which is characterized by a typical alpine meadow–steppe ecosystem, as the research area. The net primary productivity (NPP) values of Tajikistan’s grasslands from 2001 to 2022 were estimated using the Carnegie–Ames–Stanford Approach (CASA) model. In addition, 20 extreme climate indices (including 11 extreme temperature indices and 9 extreme precipitation indices) were calculated. The spatiotemporal distribution characteristics of the grassland NPP and these extreme climate indices were further analyzed. Using geographic detector methods, the impact factors of extreme climate indices on grassland NPP were identified along a gradient of different altitudinal bands in Tajikistan. Additionally, a time-lag analysis was conducted to reveal the lag time of the effects of extreme climate indices on grassland NPP across different elevation levels. The results revealed that grassland NPP in Tajikistan exhibited a slight upward trend of 0.01 gC/(m²·a) from 2001 to 2022. During this period, extreme temperature indices generally showed an increasing trend, while extreme precipitation indices displayed a declining trend. Notably, extreme precipitation indices had a significant impact on grassland NPP, with the interaction between Precipitation anomaly (PA) and Max Tmax (TXx) exerting the most pronounced influence on the spatial variation of grassland NPP (q = 0.53). Additionally, it was found that the effect of extreme climate events on grassland NPP had no time-lag at altitudes below 500 m. In contrast, in mid-altitude regions (1000–3000 m), the effect of PA on grassland NPP had a significant time-lag of two months (p < 0.05). Knowing the lag times until the effects of seasonal extreme climate events on grassland NPP will appear in Tajikistan provides valuable insight for those developing adaptive management and restoration strategies under current seasonal extreme climate conditions. Full article

Precipitation variability profoundly influences soil microbial diversity, community assembly processes, and co-occurrence networks. However, the responses of soil microbial structure to relative precipitation changes in alpine regions remain uncertain. To address this, we conducted a two-year field precipitation manipulation experiment in alpine steppe and alpine desert steppe ecosystems at the source of the Yarlung Zangbo River on the Tibetan Plateau. The experiment simulated 25%, 50%, and 75% increases and decreases in precipitation to examine how soil microbial communities respond to altered precipitation regimes. Our results reveal that microbial responses varied with precipitation magnitude, grassland type, and microbial kingdom. In the alpine steppe, bacterial α-diversity exhibited a negative asymmetric response to altered precipitation at both species and phylogenetic levels. Both bacterial and fungal species α-diversity tended to respond more strongly to changes in precipitation at high gradients in the alpine steppe than in the alpine desert steppe. Microbial co-occurrence networks in the alpine steppe were generally more responsive to altered precipitation than those in the alpine desert steppe. Furthermore, fungal α-diversity at both species and phylogenetic levels, as well as β-diversity, responded more strongly to altered precipitation than bacterial communities. These findings suggest that precipitation-driven shifts in microbial community composition and network structure vary across alpine grassland ecosystems, with fungal communities exhibiting greater sensitivity than bacterial communities. As warming intensifies precipitation variability, these microbial shifts may have cascading effects on soil biogeochemical processes and ecosystem stability, underscoring the necessity for ecosystem-specific conservation frameworks and adaptive management strategies tailored to alpine grasslands. Full article

Alpine grasslands are a critical component of the Qinghai–Tibet Plateau ecosystem, but their soil seed bank (SSB) patterns and driving mechanisms remain unclear under the influence of climate change and human activities. This study analyzed grazing exclusion (via fencing) and grazing effects using 12 sites in the alpine steppe (AS) and alpine desert steppe (AD) in northern Tibet to analyze the effects of fencing and grazing management, as well as hydrothermal and soil factors, on the SSB density and diversity. Linear regression models were applied to explore the relationships between the SSB density and environmental factors, while comparisons of the management modes revealed the potential impacts of fencing. The results show that fencing significantly increased the SSB density and diversity, especially in the AS, while grazing negatively impacted the SSB density and the Pielou evenness index. Hydrothermal factors strongly influenced the SSB in the AS, with the density positively correlated with precipitation and negatively with temperature, while responses in the AD were weak. Soil factors, such as the available phosphorus (SAP) and available potassium (SAK), were key to SSB formation in the AD, whereas ammonium nitrogen (NH4_N) and the pH were critical in the AS. Fencing optimized the hydrothermal conditions and nutrient availability, promoting SSB recovery, though its effects varied between the grassland types. This study provides scientific insights for alpine grassland restoration and sustainable management. Full article

Net ecosystem productivity (NEP) is a crucial metric for quantifying carbon storage, exchange, and cycling across global atmospheric and terrestrial ecosystems. This study examines the spatiotemporal patterns of NEP in China’s Zoigê alpine grassland and its response to climate variability, phenological changes, and soil conditions from 2000 to 2020. The results show a statistically significant increase in the annual NEP of the Zoigê Plateau, with an average rate of 3.18 g C/m²/year. Spatially, NEP displays strong heterogeneity, with higher values in the southwestern and northeastern marginal areas (>80 g C/m²) and lower values in the central region (<0 g C/m²). In alpine meadows (standardized total effect coefficient [STEC] = 0.52) and alpine steppes (STEC = 0.43), NEP is primarily regulated by soil moisture modulation, influenced by both water and temperature factors. This study accurately assesses NEP by incorporating regional soil characteristics, providing a more precise evaluation of changes in vegetation carbon sink sources in high-altitude areas. Full article

The alpine steppe has an important place in alpine ecosystems, and its distribution pattern is strongly influenced by climate change. In this study, we used “biomod2” and “FragStats 4.2” to calculate the migration trends and the habitat fragmentation of three S. purpurea alpine steppes on the western Tibetan Plateau. The results of this study show that the Stipa purpurea-Ceratoides compacta alpine steppe, the Stipa purpurea-Carex moorcroftii alpine steppe, and the Stipa purpurea-Carex montis-everestii alpine steppe are strongly influenced by climate, while other variables have less impact. Their main influence factors are annual precipitation (Bio12), precipitation of the warmest quarter (Bio18), and precipitation of the coldest quarter (Bio19), respectively. The effects of carbon emissions on the suitable habitats of all three S. purpurea alpine steppes are significant in future scenarios. Continued increases in carbon emissions will lead to a continuous reduction in their suitable habitat areas. These communities are bounded by 33° N. South of the boundary, steppe communities are influenced by mountain ranges and show a tendency to migrate to higher elevations in a southward direction. North of the boundary, steppe communities show a tendency to migrate to higher elevations in a northward direction. Climate change reduces community aggregation, leading to gradual habitat fragmentation. The findings of this study provide a scientific basis for the migration and conservation of three S. purpurea alpine steppes on the western Tibetan Plateau, thereby contributing to the improvement of ecosystem stability and species diversity. Full article

Climate variations and human activities, as two major driving forces, have profound impacts on alpine ecosystems. The Three-River Headwaters Region (TRHR) is located in the alpine region and is the source of three major rivers flowing to eastern China and Southeast Asia. Grassland is the dominant vegetation type in the TRHR and is fragile and sensitive to climate variations and human activities due to the alpine environment. Different types of grassland may have varying coping mechanisms with disturbances due to their unique environments and physiological functions. However, there is limited quantitative research on the response of different grassland types to climate variations and human activities in the TRHR. Therefore, the Carnegie–Ames–Stanford approach (CASA) was selected to simulate the net primary productivity (NPP) affected by climate (NPP_C) and the actual NPP (NPP_A) of steppes and meadows in the TRHR from 2001 to 2022, and the NPP affected by human activities (NPP_H) was calculated by subtracting the NPP_A from the NPP_C. Results showed that the NPP_A increased by 0.53 gC/m²/a during the study period, with the NPP_A of steppes and meadows increasing by 0.55 gC/m²/a and 0.51 gC/m²/a, respectively. The regions dominated by climate variations, human activities, and the combined impact of the two accounted for 22.01%, 29.42%, and 48.57% of the NPP_A changes. In terms of climate change, the impact of temperature and soil moisture on the NPP is equally important. It is worth noting that the alpine meadows (67.60%) contributed more to the increases in the NPP_A than the steppes (32.40%). In addition, climate variations and human activities contributed more to the increased total NPP_A of the meadows (20.54 GgC and 36.41 GgC) than that of the steppes (14.35 GgC and 10.20 GgC). The results clarify the quantitative evaluation system for the impact of human activities and climate change on different types of grasslands in the TRHR, providing guidance for the protection and management of these grasslands. Full article