Southeastern Qinghai-Tibetan Plateau Research Articles

The Pivotal Role of Heavy Terpenes and Anthropogenic Interactions in New Particle Formation on the Southeastern Qinghai-Tibet Plateau.

Aerosol particles originating from the Qinghai-Tibet Plateau (QTP) readily reach the free troposphere, potentially affecting global radiation and climate. Although new particle formation (NPF) is frequently observed at such high altitudes, its precursors and their underlying chemistry remain poorly understood. This study presents direct observational evidence of anthropogenic influences on biogenic NPF on the southeastern QTP, near the Himalayas. The mean particle nucleation rate (J1.7) is 2.6 cm-3 s-1, exceeding the kinetic limit of sulfuric acid (SA) nucleation (mean SA: 2.4 × 105 cm-3). NPF is predominantly driven by highly oxygenated organic molecules (HOMs), possibly facilitated by low SA levels. We identified 1538 ultralow-volatility HOMs driving particle nucleation and 764 extremely low-volatility HOMs powering initial particle growth, with mean total concentrations of 1.5 × 106 and 3.7 × 106 cm-3, respectively. These HOMs are formed by atmospheric oxidation of biogenic precursors, unexpectedly including sesquiterpenes and diterpenes alongside the commonly recognized monoterpenes. Counterintuitively, over half of HOMs are organic nitrates, mainly produced by interacting with anthropogenic NOx via RO2+NO terminations or NO3-initiated oxidations. These findings advance our understanding of NPF mechanisms in this climate-sensitive region and underscore the importance of heavy terpene and NOx-influenced chemistry in assessing anthropogenic-biogenic interactions with climate feedbacks.

Leaf Functional Traits and Their Influencing Factors in Six Typical Vegetation Communities.

Leaf functional traits (LFTs) have become a popular topic in ecological research in recent years. Here, we measured eight LFTs, namely leaf area (LA), specific leaf area (SLA), leaf thickness (LT), leaf dry matter content (LDMC), leaf carbon content (LCC), leaf nitrogen content (LNC), leaf phosphorus content (LPC), and leaf potassium content (LKC), in six typical vegetation communities (sclerophyllous evergreen broad-leaved forests, temperate evergreen coniferous forests, cold-temperate evergreen coniferous forests, alpine deciduous broad-leaved shrubs, alpine meadows, and alpine scree sparse vegetation) in the Chayu River Basin, southeastern Qinghai-Tibet Plateau. Our aim was to explore their relationships with evolutionary history and environmental factors by combining the RLQ and the fourth-corner method, and the method of testing phylogenetic signal. The results showed that (i) there were significant differences in the eight LFTs among the six vegetation communities; (ii) the K values of the eight LFTs were less than 1; and (iii) except for LCC, all other LFTs were more sensitive to environmental changes. Among these traits, LA was the most affected by the environmental factors, followed by LNC. It showed that the LFTs in the study were minimally influenced by phylogenetic development but significantly by environmental changes. This study further verified the ecological adaptability of plants to changes in environmental factors and provides a scientific basis for predicting the distribution and diffusion direction of plants under global change conditions.

Multi-Scenario Ecological Network Conservation Planning Based on Climate and Land Changes: A Multi-Species Study in the Southeast Qinghai–Tibet Plateau

The Qinghai–Tibet Plateau ecosystem is fragile, experiencing rapid changes in land cover driven by both climate change and human activities, leading to habitat fragmentation and loss and resulting in biodiversity decline. Habitat ecological networks (HA-ENs) are considered effective solutions for habitat connectivity and biodiversity conservation in response to these dual drivers. However, HA-EN studies typically rely on current or historical landscape data, which hinders the formulation of future conservation strategies. This study proposes three future scenarios—improvement, deterioration, and baseline scenarios—focused on the southeastern Qinghai–Tibet Plateau (SE-QPT). The habitats of 10 species across three classes are extracted, integrating land use and climate change data into habitat ecological network modeling to assess the long-term dynamics of HA-ENs in the SE-QPT. Finally, conservation management strategies are proposed based on regional heterogeneity. The results show the following: Climate change and human activities are expected to reduce the suitable habitat area for species, intensifying resource competition among multiple species. By 2030, under all scenarios, the forest structure will become more fragmented, and grassland degradation will be primarily concentrated in the southeastern and western parts of the study area. Compared to 1985 (71,891.3 km2), the habitat area by 2030 is projected to decrease by 12.9% (62,629.3 km2). The overlap rate of species habitats increases from 25.4% in 1985 to 30.9% by 2030. Compared to the HA-EN control in 1985, all scenarios show a decrease in connectivity and complexity, with only the improvement scenario showing some signs of recovery towards the control network, albeit limited. Finally, based on regional heterogeneity, a conservation management strategy of “two points, two cores, two corridors, and two regions” is proposed. This strategy aims to provide a framework for future conservation efforts in response to climate change and human activities.

Quantitative assessment of multi-scenario high-elevation and long-runout debris flow hazard and risk: a case study of Cuojiu Valley, south-eastern Qinghai-Tibet Plateau

Quantitative assessment of multi-scenario high-elevation and long-runout debris flow hazard and risk: a case study of Cuojiu Valley, south-eastern Qinghai-Tibet Plateau

Study of the patterns of variations in ice lakes and the factors influencing these changes on the southeastern Tibetan plateau

The ice lakes in the southeastern Qinghai–Tibet Plateau have exhibited a pronounced expansion against the backdrop of global warming, consequently amplifying the local risk of ice lake outburst disasters. However, surveys of ice lake changes in the entire region have consistently been incomplete due to the prevalent high cloud density. On the basis of Landsat remote sensing images and the Google Earth Engine (GEE) cloud computing platform, in this study, the full convolution segmentation algorithm is utilized to accurately and comprehensively map the regional distribution of ice lakes in southeastern Tibet at consistent time intervals in 1993, 2008, and 2023. Furthermore, the formation, distribution, and dynamic changes in these ice lakes are investigated. The numbers of ice lakes discovered in 1993, 2008, and 2023 were 2520, 3198, and 3877, respectively. These lakes covered areas of approximately 337.64 ± 36.86 km2, 363.92 ± 40.90 km2, and 395.74 ± 22.72 km2, respectively. These ice lakes are located primarily between altitudes of 4442 m and 4909 m. The total area experienced an annual growth rate of approximately 0.57 % from 1993 to 2023. In the present study, the long-term variations in ice lakes in each district and county are examined. These findings indicate that between 1993 and 2023, the expansion of ice lakes was more pronounced in regions with a large number of marine glaciers. Notably, Basu County presented the highest annual growth rate of the ice lake population, at 6.23 %, followed by Bomi County, at 4.28 %, and finally, Zayul County, at 2.94 %. The accelerated shrinkage of marine glaciers induced by global warming is the primary driver behind the expansion of ice lakes. The results obtained from this research will enhance our overall understanding of the complex dynamics and mechanisms that govern the formation of ice lakes while also offering valuable perspectives on the potential risks linked to their expansion in this particular area.

Facilitation drives tree seedling survival at alpine treelines

Abstract Alpine treelines are considered ecological monitors recording the impacts of climate change on trees and forests. To date, most treeline research has focused on how climate change drives treeline dynamics. However, little is known about how biotic interactions mediate treeline shifts, particularly in the case of tree recruitment, a bottleneck of treeline dynamics. We hypothesized that inter- and intraspecific facilitation determined the establishment and survival of tree seedlings at alpine treelines. To test this hypothesis, 630 Abies georgei var. smithii seedlings with different ages (4–6, 7–9 and 10–15 years old) were transplanted into three growth habitats (canopy-in, canopy-out and meadow) across the alpine treeline ecotone (4300–4500 m) in the Sygera Mountains, on the southeastern Qinghai-Tibetan Plateau. Microclimate, height growth, mortality rates and leaf functional traits of transplanted seedlings were measured over 3 years. We found that the variations in leaf functional traits were driven by microclimate. After the transplantation, the leaf concentrations of soluble sugars and starch and C:P ratio increased, whereas leaf size decreased. The resource use of seedlings gradually shifted to a more conservative strategy as indicated by changes in non-structural carbohydrates and nutrient concentrations. Radiation, temperature and moisture conditions, mediated by plant interactions, influenced seedling mortality and annual growth by affecting leaf morphological traits. Our findings illustrate how facilitation plays a crucial role in altering solar radiation and leaf trait functioning, determining seedling survival and growth at alpine treelines. We provide new insights into the underlying mechanisms for tree establishment and alpine treeline shifts in response to climate change.

Ecological response to global changes in Lake Genco, a remote alpine lake on the Southeast Tibetan Plateau, over the past two centuries

The ways in which natural ecosystems respond to global change have become an urgent concern to society. Lakes play a pivotal role in ecosystem changes because of their central position within watersheds and their involvement in various endogenous and cross-system ecological and biogeochemical processes, leaving natural archives accumulated in sediments over time. However, how lake ecosystems have responded to atmospheric changes during the past few centuries is still not fully understood. To analyse the process in more detail, we conducted a case study at Lake Genco, a remote alpine on the southeastern Qinghai-Tibetan Plateau (QTP) and recovered a 170-year history of lake's ecosystem from a 210Pb-dated sediment core. The air temperature increased between 1900 and 1950 CE and 1980 and 2020 CE. Geochemical and physical proxies (magnetic susceptibility, Sr/Ba, K/Al, Na/Al, Ti, Pb, P flux, TN and δ15Norg) indicated greater degrees of weathering and erosion, and higher nutrient loadings as terrestrial systems responded to atmospheric changes after 1900 CE. Higher primary aquatic productivity, richer biodiversity and weaker structural stability were found in Lake Genco between 1852 and 2017 CE, although the ecological response was quiet in terms of the compositional change in the diatom community, which was generally dominated by small planktonic Cyclotella ocellata. During warmer periods, diatom PC1 changed directionally due to the overall increase in the abundance of tychoplanktonic Fragilaria construens and periphytic Achnanthes minutissima and the decreasing abundance (∼10%) of C. ocellata. This study provides empirical evidence that ecological changes in remote lakes rely on interactions between the atmosphere and the landscape and helps us to understand the complexity of the various impacts of global climate change. More local and regional studies are needed to generalise the mechanism of biological responses to atmospheric changes in remote lakes, especially in the QTP.

Leaf ecological stoichiometry and anatomical structural adaptation mechanisms of Quercus sect. Heterobalanus in southeastern Qinghai–Tibet Plateau

BackgroundWith the dramatic uplift of the Qinghai–Tibet Plateau (QTP) and the increase in altitude in the Pliocene, the environment became dry and cold, thermophilous plants that originally inhabited ancient subtropical forest essentially disappeared. However, Quercus sect. Heterobalanus (QSH) have gradually become dominant or constructive species distributed on harsh sites in the Hengduan Mountains range in southeastern QTP, Southwest China. Ecological stoichiometry reveals the survival strategies plants adopt to adapt to changing environment by quantifying the proportions and relationships of elements in plants. Simultaneously, as the most sensitive organs of plants to their environment, the structure of leaves reflects of the long-term adaptability of plants to their surrounding environments. Therefore, ecological adaptation mechanisms related to ecological stoichiometry and leaf anatomical structure of QSH were explored. In this study, stoichiometric characteristics were determined by measuring leaf carbon (C), nitrogen (N), and phosphorus (P) contents, and morphological adaptations were determined by examining leaf anatomical traits with microscopy.ResultsDifferent QSH life forms and species had different nutrient allocation strategies. Leaves of QSH plants had higher C and P and lower N contents and higher N and lower P utilization efficiencies. According to an N: P ratio threshold, the growth of QSH species was limited by N, except that of Q. aquifolioides and Q. longispica, which was limited by both N and P. Although stoichiometric homeostasis of C, N, and P and C: N, C: P, and N: P ratios differed slightly across life forms and species, the overall degree of homeostasis was strong, with strictly homeostatic, homeostatic, and weakly homeostatic regulation. In addition, QSH leaves had compound epidermis, thick cuticle, developed palisade tissue and spongy tissue. However, leaves were relatively thin overall, possibly due to leaf leathering and lignification, which is strategy to resist stress from UV radiation, drought, and frost. Furthermore, contents of C, N, and P and stoichiometric ratios were significantly correlated with leaf anatomical traits.ConclusionsQSH adapt to the plateau environment by adjusting the content and utilization efficiencies of C, N, and P elements. Strong stoichiometric homeostasis of QSH was likely a strategy to mitigate nutrient limitation. The unique leaf structure of the compound epidermis, thick cuticle, well-developed palisade tissue and spongy tissue is another adaptive mechanism for QSH to survive in the plateau environment. The anatomical adaptations and nutrient utilization strategies of QSH may have coevolved during long-term succession over millions of years.

Soil microbial diversity and composition response to degradation of the alpine meadow in the southeastern Qinghai-Tibet Plateau.

With the interaction between global climate change and unreasonable human utilization, the alpine meadows on the Qinghai-Tibet Plateau have suffered various weathering degrees. Uncovering the degradation mechanism and restoration strategies can be facilitated by gaining insights into the diversity of soil microflora during meadow degradation. Therefore, we used Illumina sequencing technology to investigate the patterns of soil microbial diversity, microbial community composition, and the driving factors of microbial change in all non-degraded (ND), lightly degraded (LD), moderately degraded (MD), and severely degraded (SD) alpine meadows in the southeastern Qinghai-Tibet Plateau. Our results pointed out that with the intensification of degradation, vegetation characteristics were significantly reduced, and soil parameters significantly varied among all degraded meadows. The contents of soil organic carbon (SOC), total nitrogen (TN), available phosphorus (AN), and total phosphorous (AK) in soils decreased with the increase of degradation. The dominant bacterial phyla were the same regardless of the meadow degradation level with Actinobacteria (37.67%) and Proteobacteria (20.62%) having the highest relative abundance. Meanwhile, the dominant fungi were Ascomycota (49.9%). Based on the linear discriminant analysis (LDA) and effect size (LEfSe) method, 38 bacterial and 49 fungal species were found to be affected in the degraded alpine meadow, most of which belonged to Actinobacteria and Ascomycota, respectively. Mantel test analysis illustrated that the bacterial community was mainly significantly dependent on below-ground biomass, pH, soil organic carbon, and total nitrogen, while the fungal community was significantly dependent on soil organic carbon, total nitrogen, available nitrogen, and available potassium. These results suggest that the degeneration of alpine meadows contributes to the variability of the diversity and composition of microflora on the Tibetan plateau. Yet this effect is mainly dependent on soil factors.

Molecular phylogenetics of the Ophiocordyceps sinensis-species complex lineage (Ascomycota, Hypocreales), with the discovery of new species and predictions of species distribution

Ophiocordyceps sinensis is a famous traditional Chinese medicine adapted to the alpine environment of the Qinghai-Tibet Plateau and adjacent regions. Clarification of the species diversity of Ophiocordyceps sinensis and its relatives could expand the traditional medicinal resources and provide insights into the speciation and adaptation. The study is prompted by the discovery of a new species, O. megala, described here from a biodiversity hotspot in the Hengduan Mountains, China. Combined morphological, ecological, and phylogenetic evidence supports its distinctiveness from O. sinensis, O. xuefengensis, and O. macroacicularis. Additionally, based on the phylogenetic construction of Ophiocordyceps, a special clade was focused phylogenetically on the more closely related O. sinensis complex, which was defined as the O. sinensis- species complex lineage. A total of 10 species were currently confirmed in this lineage. We made a comprehensive comparison of the sexual/asexual morphological structures among this species complex, distinguishing their common and distinctive features. Furthermore, using the method of species distribution modelling, we studied the species ocurrences in relation to climatic, edaphic, and altitudinal variables for the eight species in the O. sinensis-species complex, and determined that their potential distribution could extend from the southeastern Qinghai-Tibet Plateau to the Xuefeng Mountains without isolating barrier. Thus, the biodiversity corridor hypothesis was proposed around the O. sinensis-species complex. Our study highlights the phylogeny, species diversity, and suitable distribution of the O. sinensis-species complex lineage, which should have a positive implication for the resource discovery and adaptive evolution of this unique and valuable group.

Short-term robust plant overcompensatory growth was observed in a degraded alpine meadow on the southeastern Qinghai-Tibetan Plateau

Plant overcompensatory growth (OCG) is an important mechanism by which plant communities adapt to environmental disturbance. However, it is not clear whether plant OCG can occur in degraded alpine meadows. Here, we conducted a mowing experiment in an alpine meadow at three degradation levels (i.e., severe degradation, SD; moderate degradation, MD; and light degradation, LD) on the southeastern Qinghai-Tibetan Plateau from 2018 to 2020 to investigate plant OCG and its relationships with soil available nutrients, plant nutrient use efficiency (i.e., nitrogen use efficiency, NUE; and phosphorus use efficiency, PUE), and precipitation. The results showed that 1) the OCG of the plant community generally occurred across all degradation levels, and the OCG strength of the plant community decreased with mowing duration. Moreover, the OCG strength of the plant community in the SD treatment was significantly greater than that in the MD and LD treatments after two years of mowing (p < 0.05). 2) In LD and MD, the soil nitrate nitrogen (NO3−) and available phosphorus (AP) concentrations exhibited a decreasing trend (p < 0.05), while the soil ammonium nitrogen (NH4+) concentration did not change from 2018 to 2020 (p > 0.05). In the SD treatment, the soil NO3− concentration tended to decrease (p < 0.05), the NH4+ concentration tended to increase (p < 0.05), and the AP concentration exhibited an inverse parabolic trend (p < 0.05) from 2018 to 2020. 3) From 2018 to 2020, plant NUE and PUE exhibited decreasing trends at all degradation levels. 4) Plant nutrient use efficiency, which is regulated by complex plant–soil interactions, strongly controlled the OCG of the plant community along each degradation gradient. Moreover, precipitation not only directly promoted the OCG of the plant community but also indirectly affected it by regulating the structure of the plant community and plant nutrient use efficiency. These results suggest that the OCG of the plant community in degraded alpine meadows may benefit not only from the strong self-regulating capacity of the plant–soil system but also from humid climatic conditions.

Origin of the Dashuigou Independent Tellurium Deposit at the Southeastern Qinghai-Tibet Plateau: Based on the Abundances of Trace Elements in the Country Rocks

Through a detailed study of the abundances and spatial-temporal distribution patterns of Te, Bi, As, Se, Cu, Pb, Zn, Au, and Ag in the rock types of different geological epochs in the Dashuigou independent tellurium deposit, and in combination with other research findings of previous researchers in this area, the authors conclude as follows: Abundances of the main ore-forming elements Te, Bi, As, Se, Au, and Ag are not high in the regional geological background, generally lower or close to their respective crustal Clark values, but almost all altered country rocks contain high levels of ore-forming elements. This indicates that the deposit’s ore-forming elements do not come from the country rocks. This also indicates that the geological thermal events that cause alteration and mineralization originate from depths and may be related to mantle plumes. Considering the distribution pattern of these ore-forming elements in the ore bodies’ hanging wall and footwall, the metallogenic mechanism may be as follows: Mineralization is not achieved through lateral secretion in the horizontal or near horizontal direction, but rather through the upward movement and emplacement of deep ore-forming elements driven by geological processes such as mantle plumes. In addition, the migration of deep ore-forming elements is not achieved through dispersed infiltration between overlying rock particles, but through non widespread concentrated penetrating channels. This type of channel is likely to be the expansion structures where faults from different directions intersect, or where linear faults intersect with circular structures.

Inventory of Glacial Lake in the Southeastern Qinghai-Tibet Plateau Derived from Sentinel-1 SAR Image and Sentinel-2 MSI Image

The glacial lakes in the Southeastern Qinghai–Tibet Plateau (SEQTP) have undergone dramatic expansion in the context of global warming, leading to several glacial lake outburst floods (GLOFs) disasters. However, there is a gap and incompleteness in glacial lake inventories across this area due to the heavy cloud cover. In this study, an updated and comprehensive glacial lake inventory was produced by object-based image analysis (OBIA) and manual vectorization based on the Sentinel-1 SAR and Sentinel-2 MSI images acquired in 2022. Detailed steps regarding the OBIA were provided, and the feature set of Sentinel-1 SAR images suitable for extracting glacial lakes was also determined in this paper. We found that the mean combination of ascending-orbit and descending-orbit images is appropriate for mapping glacial lakes. VV-polarized backscattering coefficients from ascending-orbit achieved a better performance for delineating glacial lakes within the study area. Moreover, the distribution of glacial lakes was characterized in terms of four aspects: size, type, elevation, and space. There were 3731 glacial lakes with a total area of 1664.22 ± 0.06 km2 in the study area; most of them were less than 0.07 km2. Ice-contacted lakes were primarily located in the Palongzangbo basin (13.24 ± 0.08 km2). Nyang Qu basin had the most abundant glacial lake resources (2456 and 93.32 ± 0.18 km2). A comparison with previously published glacial lake datasets demonstrated that our dataset is more complete. This inventory is useful for evaluating water resources, studying glacier–glacial lake interactions, and assessing GLOFs’ susceptibility in the SEQTP.

Late Quaternary river evolution and its response to climate changes in the upper Mekong River of the Qinghai–Tibetan Plateau

Multiple continental-scale large rivers originate from the Qinghai–Tibetan Plateau (QTP), known as the “Asia Water Tower”, because of glacial melting. However, the timing of fluvial processes in the headwaters of these large rivers and their correlation with global climate changes remain uncertain. Among these rivers, the Mekong River, the third-longest in Asia, flows through the southeastern QTP. In this study, we investigated fluvial terraces, buried paleochannels, hillslope-derived colluvium, and remnants of dammed lake in the Nangqian Basin, which is in the headwaters of the Mekong. We reconstructed the fluvial aggradation and incision history employing optically stimulated luminescence (OSL) dating. Our results suggest that orbital-scale climate changes have significantly influenced fluvial processes in the Nangqian Basin since the Late Pleistocene. During marine isotope stage (MIS) 3 (57–29 ka), a relatively warm period within the last glacial epoch, the Nangqian Basin experienced aggradation of fluvial sediment. Subsequently, during the later part of the Last Glacial Maximum (LGM) (21–17 ka), episodic landslides and debris flows caused valley infilling, resulting in river blockage and the formation of a dammed lake. At around 16 ka, the Mekong in the Nangqian Basin shifted from aggradation to fluvial incision. Since the late Holocene, the basin returned to aggradation, forming a new terrace at around 1.1 ka. This may be due to the combination of decreased stream power and increased sediment supply, potentially linked to intensified human activities and its associated vegetation degradation. Overall, our study highlights the close links between glaciation and fluvial processes in the region. Specifically, we propose that the observed aggradation pattern during the last glacial period on the plateau primarily resulted from substantial detrital input from glacier activities. The transition from aggradation to incision during the last deglacial period is likely influenced by increased discharge from glacier meltwater. The presence of colluvium interbedded within the late LGM fluvial sediment sequences highlights the significant impact of climate changes on fluvial processes in the headwater areas of the QTP, especially those events stemming from hillslope activity, such as landslides and debris flows.

Seasonal glacier change revealed from the real-time monitoring platform on Baishui River Glacier No.1 in Yulong Snow Mountain, Southeastern Qinghai–Tibet plateau

Abstract The mass balance of glaciers requires more detailed and continuous observations to understand their seasonal change in relation to climate. Here, we designed and installed an automated real-time monitoring platform at 4645 m a.s.l. on the Baishui River Glacier No.1 to collect continuous high-resolution observational data, and analyzed the seasonal dynamic from glacier movement and surface mass balance from glacier melting and snow accumulation. The results showed that the platform moved northeastward ~12.9 m at a rate of 0.06 ± 0.02 m d−1 between September 2021 and April 2022. The surface mass balance showed a varied temporal period. July and August were the main ablation periods, while ablation decreased and ceased in September. The glacier neither melted nor accumulated much between October and December, but began to have rapid snow accumulation in January. The glacier surface temperature varied with the air temperature and showed significant inter-seasonal differences among monsoon, post-monsoon and winter seasons. The surface mass balance also exhibited a strong response to the air temperature changes, with an average decrease of 1°C the point mass balance increased by 0.11 m w.e. from monsoon to post-monsoon and 0.22 m w.e. from post-monsoon to winter. Moreover, we found snowfall caused a decrease in the glacier surface temperature by increasing the surface albedo.

Distributional responses to climate change of two maple species in southern China.

Climate change is a major factor affecting biodiversity and species distribution, particularly of montane species. Species may respond to climate change by shifting their range to higher elevations. The southeastern Qinghai-Tibetan Plateau (QTP) and the Hengduan Mountains are considered as global biodiversity hotspots. However, information on the response of maple species to climate change in these regions was limited. Therefore, we selected two maple species that occur there and assessed changes in their habitat suitability under past, present and future climate scenarios in Biomod2. The results showed that temperature seasonality (bio4) was the most critical factor influencing their potential distributions. The distribution of potentially suitable habitat for Acer caesium and Acer stachyophyllum was predicted to be larger during the LGM compared to the present. Under the current climate scenario, the largest areas of potentially suitable habitat for these species were mainly located in southeastern Tibet, the Hengduan Mountains in northwestern Yunnan and western Sichuan, the Qinling-Daba Mountains in southern Gansu and the Wumeng-Daliang Mountains in northeastern Yunnan, western Guizhou and southeastern Sichuan. Under future climate change scenarios, the predicted loss of suitable habitat areas for these two species ranged from 13.78% to 45.71% and the increase ranged from 18.88% to 57.98%, with an overall increasing trend. The suitable habitat areas were predicted to shift towards the eastern parts of the QTP under both the pessimistic and optimistic future climate change scenarios in the 2050s and the 2070s, which became evident as global warming intensified, particularly in the eastern QTP and the Hengduan Mountains. Our results highlight the possibility that the diverse topography along altitudinal gradients in the QTP and the Hengduan Mountains may potentially mitigate the range contraction of mountain plants in response to climate warming. These findings provide a basis for planning conservation areas, planting and species conservation in the mountainous areas of southern China under the anticipated global warming.

A New Tool for Mapping Water Yield in Cold Alpine Regions

Watershed management requires reliable information about hydrologic ecosystem services (HESs) to support decision-making. In cold alpine regions, the hydrology regime is largely affected by frozen ground and snow cover. However, existing special models of ecosystem services usually ignore cryosphere elements (such as frozen ground and snow cover) when mapping water yield, which limits their application and promotion in cold alpine regions. By considering the effects of frozen ground and snow cover on water yield, a new version of the Seasonal Water Yield model (SWY) in the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) was presented and applied in the Three-River Headwaters Region (TRHR) in southeastern Qinghai-Tibetan Plateau (QTP). Our study found that incorporating the effects of frozen ground and snow cover improved model performance. Frozen ground acts as a low permeable layer, reducing water infiltration, while snow cover affects water yield through processes of melting and sublimation. Both of these factors can significantly impact the distribution of spatial and temporal quickflow and baseflow. The annual average baseflow and water yield of the TRHR would be overestimated by 13 mm (47.58 × 108 m3/yr) and 14 mm (51.24 × 108 m3/yr), respectively, if the effect of snow cover on them is not considered. Furthermore, if the effect of frozen ground on water yield were not accounted for, there would be an average of 6 mm of quickflow misestimated as baseflow each year. Our study emphasizes that the effects of frozen ground and snow cover on water yield cannot be ignored, particularly over extended temporal horizons and in the context of climate change. It is crucial to consider their impacts on water resources in cold alpine regions when making water-related decisions. Our study widens the application of the SWY and contributes to water-related decision-making in cold alpine regions.

Unexpectedly high nitrate levels in a pristine forest river on the Southeastern Qinghai-Tibet Plateau

River nitrate (NO3–) pollution is a global environmental issue. Recently, high NO3– levels in some pristine or minimally-disturbed rivers were reported, but their drivers remain unclear. This study integrated river isotopes (δ18O/δ15N-NO3– and δD/18O-H2O), 15N pairing experiments, and qPCR to reveal the processes driving the high NO3– levels in a nearly pristine forest river on the Qinghai-Tibet Plateau. The river isotopes suggested that, at the catchment scale, NO3– removal was prevalent in summer, but weak in winter. The pristine forest soils contributed more than 90 % of the riverine NO3–, indicating the high NO3– backgrounds. The release of soil NO3– to the river was “transport-limited” in both seasons, i.e., the NO3– production/stock in the soils exceeded the capacity of hydrological NO3– leaching. In summer, this regime and the NO3–-plentiful conditions in the soils associated with the strong NO3– nitrification led to the high riverine NO3– levels. While the in-soil nitrification was weak in winter, the leaching of legacy NO3– resulted in the consistently high NO3– levels. This study provides insights into the reasons for high NO3– levels in pristine or minimally-disturbed rivers worldwide and highlights the necessity to consider NO3– backgrounds when evaluating anthropogenic NO3– pollution in rivers.

Land use change alters phosphatase enzyme activity and phosphatase-harboring microbial abundance in the subalpine ecosystem of southeastern Qinghai-Tibet Plateau, China

In the presence of limited phosphorus (P) in terrestrial ecosystems, exploring how land use change (LUC) affects phosphatase enzyme activity and microbial communities is important for managing soil P, because microorganisms carry out the majority of P cycling in the soil through producing phosphatase enzymes. In this study, we explored the impact of LUC on P availability, phosphatase enzyme, the abundance of phosphatase-encoding genes, and microorganisms. We collected 168 soil samples at soil depths of 0–20 cm and 20–40 cm from seven sampling sites, each of which represented by four different land uses: artificial forests (AF), farmlands (FL), natural forests (NF), and shrubland (SL). We analyzed phosphatase-encoding genes and microbes from metagenome datasets. Results indicated that P availability substantially increased following NF to FL conversion. In contrast, phosphatase enzyme activity significantly decreases when NF is converted to different land uses, due to the decline of soil organic carbon (SOC), moisture content (MC) and total nitrogen (TN). We have also detected 13 P solubilizing and mineralizing genes. The phoD and gcd were the dominant mineralizing and solubilizing genes, respectively. Farmland had higher gcd gene abundance, while NF had significantly higher phoD gene abundance. The gcd gene abundance were mainly governed by pH and total P, whereas pH and available P were the primary factors controlling phoD gene. MC, SOC and TN regulated other genes detected in this study. With regard to the dominant gcd-harboring phyla, Acidobacteria, Proteobacteria, Bacteroidetes and Gemmatimonadetes were the dominant, while Proteobacteria, Acidobacteria, Actinobacteria, and Candidatus_Rokubacteria were the dominant phoD-harboring phyla. The majority of gcd and phoD-harboring microorganisms were primarily controlled by pH, available P and total P. However, some phyla also regulated by MC, SOC, and TN. In general, our findings suggested that LUC significantly alters phosphatase enzymes and the abundance of phosphate-encoding genes and microbes. These changes have significant implications for soil P cycling.

Spatiotemporal Variations in the Sensitivity of Vegetation Growth to Typical Climate Factors on the Qinghai–Tibet Plateau

Gaining knowledge about vegetation sensitivity in response to climate change is a current research priority in the context of accelerated shifts generated by global warming, especially for the Qinghai–Tibet Plateau (QTP), where vegetation is known to be highly sensitive to ongoing climate change. However, the temporal variability of vegetation sensitivity in response to climate change is still poorly understood on the QTP. Here, we articulate the interannual variability of the vegetation sensitivity in response to typical climate factors, including temperature, solar radiation, and water availability, on the QTP during 2000–2021, using a variety of indicators characterizing vegetation dynamics, including the Leaf Area Index (LAI), the Normalized Difference Vegetation Index (NDVI), the Enhanced Vegetation Index (EVI), and solar-induced chlorophyll fluorescence (SIF) data. The results indicate that temperature exerted positive impacts on forests, grasslands, and barren or sparsely vegetated areas (BSVs). However, all the land-cover types showed decreasing sensitivity to temperature variability. Solar radiation had a positive impact on forests, while it had a negative impact on grasslands and BSVs. An increasing trend was observed for forests, while a decreasing trend was found for grasslands and BSVs regarding their sensitivity to solar radiation. Water availability exerted a positive impact on grasslands and BSVs, and no obvious impact direction could be determined for forests. Over the last two decades, forests and BSVs exhibited increasing sensitivity to water availability, and no obvious trend was observed for grasslands. Overall, temperature was the most important climate factor, followed by solar radiation and water availability, regarding the regulation of vegetation sensitivity on the QTP. Spatially, temperature and solar radiation jointly dominated the vegetation sensitivity in the central to eastern QTP. Conversely, water availability dominated the sensitivity of forests in the southeastern QTP and grasslands in the northeastern and southwestern QTP. This study provides theoretical support for the ecological conservation and management of the QTP in the context of ongoing climate change.