Abstract The Tibetan Plateau is the highest and largest plateau in the world, which is also the most important ecological security barrier in China, with its vegetation serving as a critical foundation for this ecological function. The vegetation on the Tibetan Plateau has undergone drastic changes duo to climate change, human disturbances, and natural succession. A large-scale vegetation map is urgently needed for elucidating the distribution patterns of vegetation types. Based on 211 538 vegetation samples and 322 vertical vegetation zonation spectra, hierarchical and regional mapping strategies were employed to produce the vegetation map of the Tibetan Plateau (1:500 000) at the alliance level. This vegetation map accurately depicts the distribution patterns of 561 vegetation types (including 523 alliances, 32 alliance groups, 2 vegetation subformations, and 4 vegetation formations) and 12 non-vegetated types, and 61 alliances are recorded for the first time on the Tibetan Plateau. The overall accuracy and kappa coefficient are 66.76% and 0.66 at the alliance level. Compared with the vegetation of China (1:1000 000), the number of mapping units of the current vegetation map has increased from 327 to 573. The number of mapping patches has grown from 15 082 to 117 325, with the average area of patches decreasing from 171.13 to 22.00 km2. Compared with the vegetation map of China, the current map shows that forests, shrublands, grasslands, deserts, alpine sparse vegetation and agricultural vegetation have changed by 23.87%, 66.40%, 21.36%, 48.05%, 41.48%, 64.87%, respectively. This vegetation map can reflect the current vegetation distribution patterns on the Tibetan Plateau more precisely, which could provide stronger foundational supports for ecosystem management, biodiversity conservation, and national strategic decisions.

Nutrient resorption represents a key adaptive strategy for plants in nutrient-poor environments. Grazing exclusion is widely used to restore degraded grasslands; its success ultimately hinges on the population dynamics of dominant species, which drive community structural changes. However, our understanding remains limited regarding how plant nutrient utilization strategies mediated by nutrient resorption regulate these critical population dynamics. A three-year consecutive study investigated the nutrient utilization strategies of dominant species (Stipa breviflora and Cleistogenes songorica) in a desert steppe of northern China across three grazing exclusion durations: long-term (17 years), short-term (5 years), and control (0 years). The results revealed that long-term grazing exclusion significantly increased soil moisture and soil available nitrogen (N) and phosphorus (P) concentrations but decreased soil temperature, indicating that the soil microenvironment is significantly altered in fenced desert steppes. Long-term grazing exclusion significantly reduced N and P concentrations in green leaves of the two species, decreasing nitrogen resorption efficiency (NRE) and phosphorus resorption efficiency (PRE), indicating plants had reduced dependence on nutrient resorption after long-term grazing exclusion. Consequently, the reduced relative aboveground biomass of both species demonstrated a weakening of population dominance, indicating that shifts in population dynamics alter community structure in fenced desert steppes. Structural equation modeling showed that grazing exclusion indirectly decreased plant NRE and PRE through increased soil available nutrients, while directly regulating these processes via soil moisture improvement. These ecological processes ultimately decreased the species’ importance values, indicating that grazing exclusion-mediated nutrient supply restructuring reshapes ecosystem structure and function. This study reveals a shift in plant nutrient strategy in fenced desert grasslands from an internal cycling-dominated model to an external access-dominated model and provides a theoretical framework for understanding community succession in fenced grasslands from the perspectives of micro-physiological processes and macro-population dynamics.

The K-fluorescence technique exhibits superior monochromaticity and a uniform radiation field, making it highly suitable for elemental analysis. In this study, a K-fluorescence radiation device was employed to conduct X-ray fluorescence (XRF) analysis on five groups of ancient human bone samples spanning a temporal range of 5000 years. Preliminary identification of elemental compositions was achieved, enabling the revelation and inference of historical insights embedded within these ancient remains. During the experiment, the Si-PIN semiconductor detector was calibrated by using four standard radioactive sources with known energies, such as 55Fe, 109Cd, 57Co and 125Eu, and the detection efficiency of the detector at different energies was understood by Geant4 simulation to optimize the experimental settings. The results show that the characteristic peaks of calcium (Ca), iron (Fe), and strontium (Sr) appear in all the bone samples of different periods, and the energy spectra of the bone samples of the Ming Dynasty show anomalous heavy metal elements copper (Cu) and arsenic (As). With the historical background, the presence of heavy metal elements in the samples of the official eunuchs of the Jiajing period of the Ming Dynasty is analyzed to be related with the fact that the Ming Dynasty Emperor Shizong was fond of longevity and was obsessed with alchemy.

The first pathfinder of the CATCH mission, CATCH-1, was launched in June 2024. It is equipped with a light-weight, narrow-field optimized Lobster Eye X-ray Optics. By sacrificing a portion of the field of view to achieve a large effective area, the telescope’s sensitivity is enhanced. This paper presents the equipment and procedures employed for calibrating the optics assembly. A comprehensive on-ground calibration for the Lobster Eye X-ray Optics is conducted before its launch using multi-target X-ray sources and the pnCCD Color X-Ray Camera in the 100 m X-Ray Test Facility. The results are derived from calibration measurements taken before and after the mechanical testing and mainly include measurements of the focal length, point spread function, angular resolution, and the effective area for incident X-rays at 0.28 keV, 0.93 keV, 1.49 keV, 2.98 keV, and 4.51 keV. The results indicate that the mirror’s performance remains stable and no observable variation before and after the mechanical testing. At 0.93 keV, the mirror’s angular resolution is 6.11^' (FWHM), and the effective area is 40.75 cm^2 , meeting the expected performance of CATCH-1 X-ray optics.

Accurate measurement of high-flux synchrotron X-rays has become crucial for progress in plasma diagnostics and thermal nuclear fusion studies. A free-air ionization chamber and a low-current measurement system were developed to replicate high-flux monochromatic X-ray air kerma values. This system enables simultaneous measurement of ionization currents from the monitor chamber, free-air ionization chamber, and transfer detector, establishing a metrological standard for synchrotron radiation monochromatic X-ray flux. The correction factors of air attenuation, recombination loss and electron loss in the free-air ionization chamber were studied by means of a combination of experiment and theoretical simulation. Absolute measurements of air kerma were performed using monochromatic synchrotron X-rays in the energy ranges of (6-20) keV and (20-70) keV at the 4W1A beamline of the Beijing Synchrotron Radiation Facility (BSRF) and the BL13W1 beamline of the Shanghai Synchrotron Radiation Facility (SSRF), respectively. Through systematic uncertainty evaluation, the combined standard uncertainty of the air kerma measurements was determined to be 0.61%. By establishing the quantitative relationship between air kerma and photon flux, the monochromatic X-ray flux rates across the (6-70) keV energy range were derived with a combined standard uncertainty of 2.57%. The quantity transfer experiment of the transfer detector was carried out on the synchrotron radiation source, and the reliability of the measurement results was verified by indirect comparison with the calibration results of the PTB.

The enhanced X-ray Timing and Polarimetry (eXTP) mission is China’s future flagship X-ray astronomy observatory. The eXTP payload comprises an array of Wolter-I focusing mirrors that utilize nickel electroforming technology. The testing and calibration of the eXTP mirror assemblies will be primarily conducted at the 100 m X-ray Test Facility (100XF) at the Institute of High Energy Physics, with support from the PANTER facility of the Max Planck Institute for Extraterrestrial Physics. Consequently, cross-calibration between the facilities is essential. This paper presents preliminary cross-calibration for mirror module 3 of the eXTP focusing mirror, conducted at both the 100XF and PANTER facilities, focusing on point spread functions (PSFs), vignetting, and effective area. The angular resolutions obtained at the two facilities are 21 . ″ 8 ± 0 . ″ 2@Al–K α , 29 . ″ 8 ± 0 . ″ 5@Cu–K α (100XF), as well as 21 . ″ 9 ± 0 . ″ 2@Al–K α , 27 . ″ 6 ± 0 . ″ 5@Cu–K α (PANTER). The measured effective area results at 100XF are 52.0 ± 0.7 cm 2 @Al–K α , 12.1 ± 0.1 cm 2 @Cu–K α . Meanwhile, after correcting for beam length (or divergence angle), the results from PANTER are 52.8 ± 0.7 cm 2 @Al–K α , 12.2 ± 0.2 cm 2 @Cu–K α . The cross-calibration results validate the reliability of the calibration methodologies for eXTP mirrors. Consistent outcomes in alignment, focus search, and PSFs were achieved, satisfying stringent mission requirements. Effective area measurements showed good agreement with simulations, with deviations limited to ±10%. These cross-calibration results provide valuable references for subsequent mirror calibrations and corrections, especially concerning effective area calibration, which should be a key focus of future research efforts.

Understanding biomass allocation patterns is critical for predicting plant adaptation strategies under climate change scenarios. At present, the theory of biomass allocation (optimal allocation and equidistant allocation) is still controversial, especially in the “fragile” desert steppe, which is especially sensitive to climate change. Therefore, we set up four treatments with varying precipitation gradients [natural precipitation reduced by 50 % (W-50 %), control (WCK), natural precipitation increased by 50 % (W+50 %), and natural precipitation increased by 100 % (W+100 %)] in the desert steppe of Inner Mongolia and applied them for six years before analyzing the trade-off relationship between aboveground and below-ground biomass, verifying the distribution theory, and considering the factors affecting change in biomass distribution. Our findings revealed that the aboveground biomass increased significantly with the increase of precipitation gradient, while the below-ground biomass was significantly different between years. Desert steppe plants allocated more biomass to the below-ground and followed the optimal allocation theory, W-50 % amplified the trade-off of biomass to the belowground, W+50 % and W+100 % treatments transferred the biomass aboveground instead, which claimed that both plant diversity and soil physicochemical properties regulate biomass allocation. At W-50 % treatment, plant growth was limited by soil water content. At W+50 % and W+100 % treatments, plants were limited by soil available nutrients. The “opportunistic” strategy of annual herbs explains why biomass was re-directed to the aboveground organs. Our results emphasize desert plants can adapt to precipitation change using high variation and optimal biomass allocation.

Precipitation significantly influences the composition and structure of grassland ecosystems, particularly in arid desert steppes. Stipa breviflora, as a keystone species, plays a crucial role in maintaining the stability of the desert steppe. However, the response of S. breviflora's succession strategy to changes in precipitation within the community remains uncertain. Since 2016, this research was conducted in a desert steppe in Inner Mongolia, China, involving control precipitation (PCK), and increases of 50% (P50) and 100% (P100) in natural precipitation. We measured biomass, height and canopy cover, calculated the importance value (IV) by species, and assessed the photosynthetic parameters and leaf elemental content of S. breviflora in 2021 and 2022. Results showed that the increase of precipitation significantly reduced the IV of S. breviflora. The net photosynthetic rate, transpiration rate, stomatal conductance, aboveground biomass carbon content and aboveground biomass nitrogen of S. breviflora leaves grew considerably in experimental plots receiving more precipitation, while delta 13C value of leaves decreased significantly. Linear regression analysis and structural equation model showed that although the increase of precipitation improved the adaptability of S. breviflora functional traits and increased its IV, a higher transpiration rate significantly contributed to the decrease in its IV. Consequently, our research reveals the succession strategy of S. breviflora and provides a theoretical basis for studying the response mechanisms of desert steppe plant communities to climate change. (sic)(sic) (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(Stipa breviflora)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic),(sic)(sic)(sic)2016(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(PCK),(sic)(sic)50% (P50)(sic)(sic)(sic)100% (P100)(sic)(sic).(sic)2021(sic)2022(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic);(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),delta C-13(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).

As a core tool in precision detection technology, the monochromaticity and flux stability of monoenergetic X-rays directly impact experimental accuracy in applications such as detector calibration. There is an urgent need to overcome the limitations of conventional radioisotope sources (fixed energy) and Bragg diffraction systems (low diffraction efficiency). Leveraging the unique properties of LiF(200) crystal-specifically its high reflectivity and low thermal expansion coefficient-this study constructed a Bragg diffraction-based monoenergetic X-ray apparatus. By adjusting the Bragg angle via a θ-2θ goniometer and performing energy-dispersive spectroscopy (4-48.32 keV) using a Fast-SDD detector, the system's performance was characterized. Geant4 simulations were employed to model the detector geometry, while standard K-series characteristic X-ray sources calibrated the energy linearity and energy resolution. Comprehensive analysis evaluated the apparatus' energy response, energy resolution, and monochromaticity. Results demonstrate that the system achieves: Monochromaticity < 2.2% within 4-48.32 keV, count rate of 3166 cps at 10 keV. This provides a viable bench-top alternative for optimizing high-precision X-ray analytical instrumentation and supporting synchrotron radiation experiments.

BACKGROUND:The Qinghai-Tibet Plateau, regarded as an ecological security barrier for Asia, has grassland ecosystems that are highly sensitive to climate change and anthropogenic disturbances. Neotrinia splendens, known for its remarkable nutrient and geographical distribution adaptability, plays a crucial role in regulating the structure and function of the plant community in the northern Qinghai-Tibet Plateau. However, the biogeographic patterns and underlying driving mechanisms of the nutrients and population traits remain poorly understood. Based on 83 N. splendens grassland sites in the northern Qinghai-Tibet Plateau, the aboveground nutrient concentrations and population traits of N. splendens were measured and analyzed, combined with soil physicochemical and climatic factors. RESULTS:Along the longitude gradient, soil organic matter, total nitrogen, total phosphorus, available nitrogen (SAN) and phosphorus (SAP), plant Carbon (C), nitrogen (N), and phosphorus (P) concentrations significantly increased, whereas these decreased with increasing latitude and altitude gradients. Population height, cover, and density showed the same biogeographical pattern as soil and plant nutrients. Mean annual temperature (MAT) and mean annual precipitation (MAP) induced by longitude, latitude, and altitude gradients indirectly altered plant C, N, and P concentrations by directly regulating SAN and SAP concentrations, affecting plant height and cover. CONCLUSIONS:This study enhances the understanding of the biogeographic patterns of plant nutrients and population traits on the grasslands of Qinghai-Tibet Plateau, provides insights to deepen multiple adaptations of plants to environmental stresses, and elucidates the multi-scale driving mechanisms of nutrient cycling in grassland ecosystems through the climate-soil-plant-population ecological cascades.

X-ray interferometer is a measurement device based on the theory of X-ray interferometry, capable of achieving atomic-level precision in displacement measurement and studying a novel method for defining and replicating measurement units based on the lattice constant of silicon. High monochromaticity, high stability, and high-throughput monochromatic X-ray sources, along with their corresponding detection systems, are critical components of an X-ray interferometer. This paper employs the Bragg diffraction principle to construct a high-stability, high-monochromaticity monochromatic X-ray source device. The device utilizes a copper target as the X-ray source and a Si(220) crystal as the monochromator. To facilitate testing of the monochromatic X-ray source and subsequent X-ray interferometer research, the detection module consists of an SDD detector and an imaging CCD detector. The SDD detector was calibrated at the Hard X-ray Calibration Facility of the China National Institute of Metrology in Changping Campus, including detection efficiency testing, energy resolution calibration, and energy linearity calibration.

The Einstein Probe mission is an astronomical satellite developed in China, focusing on time-domain astronomy in the soft X-ray energy band. A key payload of this mission is the follow-up X-ray telescope (FXT), which is the result of international collaboration between China and Europe. The FXT features gold-coated nickel Wolter-I-type focusing mirrors and utilizes PNCCD detectors for imaging and spectroscopy in the focal plane. We reviewed the seven-year development history of the FXT. Initially, the configuration of the FXT consisted of a single telescope unit in 2017, but it later evolved into a dual-unit setup. Building on the successful design of eROSITA, the FXT team has innovatively introduced new operational modes for the PNCCD. FXT team also developed an ultra-compact helium pulse tube refrigerator, which cools the PNCCD down to -90 ^∘ C. Additionally, various passive shielding measures have been implemented to protect against high-energy charged particles and enhance radiation resistance. These advancements have significantly improved the overall performance and reliability of the FXT. The ground calibrations and tests of the FXT demonstrate that its primary performance meets the established design goals. The FXT has exhibited outstanding performance in orbit, establishing itself as one of the space X-ray telescopes with considerable international influence.

Desert steppe ecosystems are very sensitive to climate change. Although precipitation is known to promote carbon exchange and biomass production, quantitative assessments of C3/C4 species dynamics and carbon-water coupling mechanisms under long-term precipitation manipulation remain limited. Here, we conduct a five-year rainfall control experiment in the Stipa breviflora desert in Inner Mongolia, China, employing four treatments: 50 % reduced precipitation, natural precipitation, 50 % increased precipitation, and 100 % (doubled) precipitation. We measured gas exchange in each plot with a portable photosynthesis system Li-6400 and measured aboveground biomass of C3 and C4 species during the growing season (May-October). The results demonstrated that elevated precipitation enhanced ecosystem carbon exchange, driven by a linear increase in C3 species biomass, with a 100 % precipitation increase significantly strengthening carbon sink capacity. Conversely, the carbon sink function of C4 species declined under drought (reduce precipitation by 50 %). These findings suggest that C3 biomass dominates carbon-water coupling, while C4 species buffers drought effects, collectively stabilizing ecosystems under extreme precipitation.

The Follow-up X-ray Telescope (FXT) is one of the main scientific instruments on board the Einstein Probe astronomical satellite, which was launched in 2024 January. FXT consists of two Wolter I type nested telescopes (FXT-A and FXT-B) with a focal length of 1600 mm. The focal plane detector employs a PNCCD with 384 x 384 pixels. The timing mode of FXT serves as the primary operating mode for fast X-ray timing observations. To evaluate and validate the timing performance of FXT prior to launch, a comprehensive timing calibration was performed at the 100 m X-ray test facility. By simulating various periodic Crab-like profiles using the Grid Controlled X-ray Tube (GCXT) in conjunction with a pulsar simulation module, it was verified that the relative time accuracy of FXT exceeds 5 x 10(-9). Furthermore, employing GCXT with a voltage pulse generation module enabled the determination of the time resolutions for FXT-A and FXT-B, recorded as 45.6 +/- 2.7 mu s and 47.1 +/- 2.8 mu s, respectively. An absolute timing calibration for FXT-B was carried out using the GCXT and a time interval analyzer, revealing a measured time delay of 3.9 +/- 2.1 mu s for FXT-B.

The Follow-up X-ray Telescope (FXT) is one of the two main scientific instruments on board the Einstein Probe astronomical satellite, which was launched in 2024 January. FXT focuses on the energy range of 0.3-10 keV and mainly conducts follow-up observations of transients and burst sources. It consists of two units of completely independent optical system and detector system (FXT-A and FXT-B). The focal plane detector adopts PNCCD provided by Max Planck Institute for Extraterrestrial Physics. FXT was designed to have three operating modes with different integration times and readout schemes, namely full-frame mode, partial-window mode and timing mode. We conducted a detailed calibration for PNCCD at the Institute of High Energy Physics before launch. Our results demonstrate that both FXT-A and FXT-B exhibit excellent spectral performance. The energy resolution (Full Width at Half Maximum) of FXT-A and FXT-B are both better than 85 eV at 1.487 keV. We determined a mean equivalent noise charge around 2.8 e- for FXT-A and FXT-B in three operating modes at -90 degrees C +/- 0.5 degrees C, except for a few noisy pixels in full-frame mode. In addition, we measured the relation of charge transfer inefficiency as function of photon energy and confirmed the ability to detect photons in the energy range of 0.3-10 keV. These calibration results have been ingested into the initial version of calibration database and applied to the analysis of scientific data acquired by FXT.

Community stability plays a vital role in ensuring the consistent provision of ecosystem services despite climatic changes. It is presumed that future changes to annual precipitation will impact the ecological stability of many systems, particularly the ‘fragile’ desert steppe. However, most studies of ecological stability are inferred from short-term field precipitation manipulation experiments. There is still extensively to learn regarding how the desert steppe reacts to long-term changes in precipitation. We conducted a 7-year experimental study monitoring the aboveground biomass of major plant functional groups (perennial grasses, perennial forbs, annual herbs, and semi-shrubs) under four experimentally manipulated precipitation gradients [reducing natural precipitation by 50% (-50%), natural precipitation (CK), increasing natural precipitation by 50% (+50%), and increasing natural precipitation by 100% (+100%)] to evaluate how changes in precipitation affect the biomass stability of plant communities. We did observe higher levels of species asynchrony, resistance, resilience, and temporal stability of community and functional groups in experimental plots receiving more precipitation. Interestingly, the contribution of species richness to community stability was not observed in our experiment. The increase in soil water content in the 20-30cm soil layer caused by increased precipitation promoted the resilience of perennial grasses but inhibited the resistance of perennial forbs. At the same time, the decrease in soil inorganic nitrogen caused by increased rainfall inhibited the resilience of perennial grasses. Notably, community resilience predominantly hinged on the resilience of perennial grasses, while community resistance was primarily dictated by the resistance of perennial forbs. Moreover, species asynchrony emerged as the primary regulator of community temporal stability. Our long-term experimental evidence underscores the transformative potential of precipitation in reshaping grassland stability across both functional and structural dimensions. Importantly, sustaining the high stability of perennial herbs emerges as a strategic avenue for enhancing the ecological stability of the desert steppe in the face of evolving precipitation patterns.

Located in the northeast of the Qingzang Plateau,the Qaidam Basin is a huge plateau-type closed basin.The vegetation is dominated by desert,including swamp wetlands,halophytic meadows and montane grasslands.In order to show the species composition,community characteristics and distribution pattern of vegetation on the Qaidam Basin in more details,this study used the field data of the Second Tibetan Plateau Scientific Expedition and Research of 2022 and the Comprehensive Scientific Investigation of the Data-scarce Area of the Qinghai-Tibet Plateau of 2014,including 157 sample plots and 458 sample plots,which are integrated into the sample data set of plant communities in Qaidam Basin.Through the collation and compilation of data,a total of 185 species information was obtained,among which the families with the largest number of species were Asteraceae(39 species),Poaceae(33 species),Fabaceae(17 species),Amaranthaceae(16 species)and Brassicaceae(10 species),and the genera with the largest number of species were Stipa,Artemisia,Astragalus,Oxytropis and Saussurea.The composition of plant life forms is dominated by herbs,accounting for 78.37％.The species of middle Asia account for 41.62％of the geographical composition of the flora.Based on the phytocoenological-ecological principles,157 sample plots can be classified into 4 Vegetation Formation Groups,7 Vegetation Formations,11 Vegetation Subformations and 40 Alliances.This data set can provide the most original basic data for the in-depth exploration of vegetation characteristics in the Qaidam Basin,the compilation and research of the Vegegraphy of China,and the mapping of the Qingzang Plateau and the national vegetation map.

A five-year rainfall control experiment was conducted in-field on the Stipa breviflora desert steppe in Inner Mongolia, China. We set four precipitation gradients on the fenced grassland: reduce precipitation by 50%, P1; natural precipitation, P2; increase precipitation by 50%, P3; increase precipitation by 100%, P4. We used a portable photosynthesis system Li-6400 measured the ecosystem carbon and water fluxes of each plot during the growing season (May-October). Results showed that precipitation had a significant impact on ecosystem carbon exchange. With increasing precipitation, net ecosystem carbon exchange (NEE), ecosystem respiration (ER), gross ecosystem productivity (GEP), evapotranspiration (ET) and water use efficiency (WUE) increased by 1.89, 0.37, 2.21, 0.80 µmol·m-2·s-1 and 2.16 µmol·mmol-1, respectively. NEE、ER、GEP、WUE is more sensitive to precipitation. Increasing precipitation will significantly increase the aboveground biomass of C3 species and promote carbon flux. In summary, increasing precipitation will increase carbon flux and promote carbon sink on the desert steppe.

The arid region of the Qinghai-Tibet Plateau has a harsh natural environment that spans a vast altitudinal range, where plant growth suffers from various environmental stresses such as low temperature and drought. Shrubs are one of the most important plant functional groups in this region, and different shrub types have developed various nutrient strategies in response to these environmental stresses. However, nutrient characteristics and biogeographical patterns in different shrub types have seldom been investigated. The aboveground concentrations of carbon (C), nitrogen (N), and phosphorus (P) of the three shrub types (leaf-normal, leaf-reduced, and succulent shrubs) and soil physicochemical properties were measured in 138 sampling sites in the arid region of the Qinghai-Tibet Plateau. Mean C, N, and P concentrations in all shrubs were 382.09 mg/g, 24.63 mg/g, and 1.43 mg/g in the arid region of the Qinghai-Tibet Plateau. Mean C, N, and P concentrations were 347.64, 24.30, and 1.25 mg/g in succulent shrubs, which were significantly lower than those of leaf-normal shrubs (C: 418.43 mg/g; N: 24.57 mg/g; P: 1.55 mg/g) and leaf-reduced shrubs (C: 399.71 mg/g; N: 25.96 mg/g; P: 1.65 mg/g). With increasing in longitude, C, N, and P concentrations in leaf-normal and leaf-reduced shrubs increased but these nutrients in succulent shrubs decreased. Increasing altitude only increased N and P concentrations for leaf-normal shrubs. These results demonstrated that the three shrub types had divergent nutrient biogeographical patterns. N and P concentrations of leaf-normal and leaf-reduced shrubs were directly driven by soil total N and total P concentrations and indirectly regulated by mean annual temperature and mean annual precipitation, promoting the formation of longitude or altitude nutrient patterns. Meanwhile, N and P concentrations in succulent shrubs were only regulated by soil pH, total N, and total P concentrations, driving the formation of longitude nutrient patterns. These results indicated divergent driving factors for nutrient biogeographical patterns among the three shrub types. Our study highlights the unique nutrient characteristics of succulent shrubs, reveals driving factors of nutrient biogeographical patterns in the three shrub types, and contributes to the understanding of biogeochemical cycling in arid ecosystems.

The Follow-up X-ray telescope (FXT) is one of the instruments on board the Einstein Probe (EP) satellite of the Chinese Academy of Sciences (CAS) which was launched in January 2024. The EP mission is dedicated to the study of time-domain high-energy astrophysics, utilising a lobster-eye-based wide-field telescope, complemented by an eROSITA-like optics for follow-up observations. MPE has provided hardware and conducted measurement campaigns at its test facilities as part of a European contribution to Einstein Probe by ESA, and in addition the eROSITA flight spare mirror assembly as the second FXT module. Three FXT mirror assemblies – structural-thermal, qualification and flight models – have been manufactured. All components underwent acceptance testing using X-rays, followed by the installation of X-ray baffles for stray-light rejection. Subsequently, they underwent environmental tests and X-ray performance evaluations. The final tests of the qualification model, serving as a flight spare, and the flight model included an X-ray calibration at various photon energies ranging from about 0.3keV to 8keV. All tests were performed at MPE’s test facilities: the laboratory for vibration and thermal-vacuum testing, and the PANTER X-ray facility. Reported are the setups and the results of the respective test sequences, focusing on the qualification and flight mirror assemblies. After delivery to China, all mirror assemblies were subjected to complementary measurements in the X-ray test facility of the Institute for High Energy Physics (IHEP) of CAS.