Northeast Qinghai-Tibet Plateau Research Articles

Early warning signals of grassland ecosystem degradation: A case study from the northeast Qinghai-Tibetan Plateau

As a typical vulnerable ecosystem, alpine steppes can be subject to nonlinear accelerations in degradation, once tipping points are reached or exceeded, and thus far more effort and investment will be needed, to reverse the degraded status of such ecosystems, if effective preventive measures or interventions are not adopted sufficiently early. Thus, detecting early warning signals of tipping events is extremely important for ecosystem protection and recovery, but remains highly challenging. For alpine steppes, coverage or biomass loss and species invasion are both key transitions. Using multi-source data, including ground surveys and remote sensing images with different resolutions, we tried to screen and identify potential early-warning signals for alpine grassland degradation events and analyze their efficacy. The results showed that the degradation levels derived from spatial heterogeneity information combined with a vegetation index were reliable, as was verified by ground surveys, and could illustrate the degradation process of a grassland ecosystem. Six common early-warning signals (variance, skewness, and autocorrelation, from both the spatial and temporal domains) were tested according to degradation degree, and spatial autocorrelation and temporal autocorrelation had the best performances, as they could indicate different degradation levels, and the change trends of temporal autocorrelation could provide early-warning functions. A waved change of spatial variance could reflect a vegetation growth dynamic that might indicate species invasion. In this study, the threshold values of spatial and temporal autocorrelation were 0.7 and 0.2, respectively, and from these, the thresholds of vegetation coverage and biomass were then obtained. However, these signals and thresholds had some limitations during application. These findings provide insights into better understanding of the alpine grassland degradation process, and contribute to a better management approach for vulnerable ecosystems using early-warning methods.

Plant stoichiometric hierarchical responses to nutrient enrichment can enhance understanding regarding the process of biodiversity loss

In this study, our objective was to determine whether plant stoichiometry following nitrogen (N) and phosphorous (P) enrichments can enhance understanding regarding biodiversity loss processes. Thus, we conducted a field experiment involving N, P, and N + P enrichments in a sub-alpine meadow on the northeast of Qinghai-Tibet Plateau within the 2009–2014 period. Plant stoichiometric patterns were investigated using six exemplar species, four functional group levels, as well as the community level. The hierarchical responses of species richness, dominance, plant height, and plant ecological stoichiometry to nutrient addition were investigated. Further, step-wise regression analysis was performed and a structural equation model (SEM) was constructed to assess the linkages between ecological performances and plant stoichiometric characteristics. The model was also used to quantify the contributions of stoichiometric characteristics as drivers of changes in species richness. Our results indicated that N-only and N + P enrichments significantly reduced species richness at community-level, while enhancing grass richness and dominance. Furthermore, only the responses of the N:P ratio, P-related stoichiometry (P concentration, C:P ratios, and N:P ratio), and plant C:N:P stoichiometry to N, P, and N + P fertilizations, at community level could be mirrored at functional group and species levels. Additionally, the responses of the plant N contents and C:N ratios of different species and functional groups showed 28% similarity following nutrient addition. However, at functional group level, only 10% of these responses were similar to those observed at community level, and only in grasses and at community level did the stoichiometric responses show any convergence. We also observed that the major factors affecting ecological performance at different levels included plant N contents and C:N ratios. The species dominance of Elymus nutans (E.n) and the functional group dominance of grasses increased with increasing plant N concentration, and in terms of species richness, species, functional group, and community level stoichiometric traits could fully explain 43% of the observed species richness trend. Further, the effect of the community C:N ratio on species richness was significantly positive. Those results indicated stoichiometric responses to N and P fertilization did not entirely show scale-independence. Moreover, in a N-limited community, plant differences with respect to nitrogen content flexibility and nitrogen use efficiency can serve as key drivers in explaining ecological performance. Community C:N ratios showed suitability for used in the prediction of species richness trends, and to clarify changes in biodiversity, it is necessary to investigate stoichiometric traits at functional group level.

Spatial variation of water stable isotopes of multiple rivers in southeastern Qaidam Basin, northeast Qinghai-Tibetan Plateau: Insights into hydrologic cycle

River contains plenty of information on hydrological cycle. The water stable isotope approach is a powerful tool to unravel the hydrological processes such as river water sources, evaporation and river water-groundwater interaction. However, the spatial variation and influencing factors of stable isotope compositions in multiple rivers within a large basin and their indication to hydrological cycle have been less documented. This work reports on the spatial variation of stable water isotopic compositions of river water of four rivers and the underlying hydrological processes in the southeastern Qaidam Basin, northeast Qinghai-Tibetan Plateau, China. The results show that the δD and δ18O values of individual river vary along the river flow directions (generally from south to north), and that of multiple rivers also exhibit an obvious spatial variation, which is mainly influenced by evaporation, groundwater discharge, moisture source and transport pattern and local precipitation. As for an individual river, the δD and δ18O of river water are gradually enriched by evaporation along the river flow direction, which are rapidly depleted due to groundwater discharge into river in the groundwater overflow zone. For multiple rivers, the stable isotopic compositions of river water are gradually depleted from the west to the east of the study area (i.e. approximately perpendicular to rivers’ flow directions), which are mainly controlled by moisture source and transport pattern. This study helps to enhance our understanding of the hydrological cycle in a large basin through combined analysis of water stable isotopic data from individual river and multiple rivers. The data evaluation methods and results of this study could be useful in other areas to understand hydrological processes and moisture transport pattern.

Study of the Interseismic Deformation and Locking Depth along the Xidatan–Dongdatan Segment of the East Kunlun Fault Zone, Northeast Qinghai–Tibet Plateau, Based on Sentinel-1 Interferometry

The East Kunlun fault zone (EKFZ), located northeast of the Qinghai–Tibet Plateau, has experienced several strong earthquakes of magnitude seven or above since 1900. It is one of the most active fault systems and is characterized by left-lateral strike-slip. However, the Xidatan–Dongdatan segment (XDS) of the East Kunlun fault zone (EKFZ) has had no earthquakes for many years, and the Kunlun Mountains MS 8.1 earthquake has a stress loading effect on this segment, so it is widely regarded as a high-risk earthquake gap. To this end, we collected the Sentinel-1 data of the XDS of the EKFZ from July 2014 to July 2019 and obtained the high-precision interseismic deformation field by the Interferometric Synthetic Aperture Radar (InSAR) technique to obtain the slip rate and locking depth of the XDS of the EKFZ, and the seismic potential of the segment was analyzed. The results are as follows: (1) The LOS deformation field of the XDS of the EKFZ was obtained using Sentinel-1 data of ascending and descending orbits, which indicated that the XDS of the EKFZ is dominated by horizontal motion. Combined with the interference results, it is shown that the strike-slip rate dominates the deformation information of the XDS of the EKFZ. The deep strike-slip rate of the fault is about 6 mm/yr, the deep dip-slip rate is about 2 mm/yr, and the slip-deficit rate on the fault surface is about 6 mm/yr; (2) Combined with the spiral dislocation theory model, the slip rate of the XDS to Xiugou Basin of the EKFZ has a gradually increasing trend, with an average slip rate of 9.6 ± 2.3 mm/yr and a locking depth of 29 ± 5 m; (3) The stress accumulation is about 483 ± 92 years in the XDS of the EKFZ, indicating that the cumulative elastic strain energy of the XDS can produce an MW 7.29 ± 0.1 earthquake in the future.

Simulation of Soil Temperature under Plateau Zokor's (Eospalax baileyi) Disturbance in the Qinghai Lake Watershed, Northeast Qinghai-Tibet Plateau.

The soil temperature is a key factor affecting the fragile terrestrial ecosystems on the Qinghai-Tibet Plateau, and has been remarkably altered by the soil mammal's disturbance. This study first analyzed the soil temperature variation in grassland, mound, and bald patch under the disturbance of plateau zokor (Eospalax baileyi) from October 2018 to July 2020 in the Qinghai Lake watershed. Then, the SHAW (simultaneous heat and water) model was used to simulate the soil temperature change of three land surface types, and the sensitivity of soil temperature to environmental parameters before and after the disturbance was explored. The results showed the following: (1) The daily range of soil temperature was mound > bald patch > grassland, which became smaller as the depth increased, due to the co-influence of vegetation coverage and soil bulk density. There was an obvious hysteresis of soil heat transfer for grassland, as compared with mound and bald patch, especially at 5 and 15 cm depths. (2) The SHAW model was applicable for the simulation of soil temperature under the plateau zokor's disturbance, especially during the growing season, and had better simulation accuracy for deep soil. (3) Air-entry potential and pore-size distribution index obviously affected soil temperature change, because of the change in root system and soil pores under the plateau zokor's disturbance. With the evolution of disturbance process, the response of soil temperature to the leaf area index weakened gradually, owing to the different duration of disturbance and restoration. In general, the plateau zokor's disturbance alters the soil properties and vegetation characteristics, and further, distinctly affects heat transfer and soil temperature.

Plant drought adaptation strategies regulate alpine grassland water yield in the Qinghai Lake Basin, northeastern Qinghai-Tibet Plateau

Study regionThe Qinghai Lake Basin, northeast Qinghai-Tibetan Plateau. Study focusVegetation dynamic induced change on catchment water yield (including surface runoff and groundwater runoff) is one of the research hotspots in the field of hydrology and ecology. However, few studies have explored the underlying biological mechanism by which plant regulate water yield. In this study, we examined the impact of different plant drought adaptation strategies on watershed water yield in the Qinghai Lake Basin, using both the ecohydrological model, water balance method and surface runoff experiments. New hydrological insightswe defined two type of plant drought adaptation strategies: drought-avoiding strategy can maximize the soil moisture and therefore minimize vegetation water stress, while drought-tolerating strategy tends to increase productivity by tolerating a certain degree of water stress. The result shows that plants employing drought-avoiding strategy have significantly higher water yield and water yield coefficient (the ratio of water yield to precipitation) than plants adopting drought-tolerating strategy, regardless of meadow or steppe species. Meanwhile, for all grassland species in the study region, plants with drought-avoiding strategy have less vegetation cover and net primary productivity than plants with drought-tolerating strategy, which reflect the trade-off between avoiding water stress and achieving competitive advantages. Our findings offer insights into the biological mechanism by which vegetation regulates water yield, and provide vital guidance for watershed management.

Structural Properties of Quinoa Protein Isolate: Impact of Neutral to High Alkaline Extraction pH.

In this work, we extracted proteins from white quinoa cultivated in the northeast of Qinghai-Tibet plateau using the method of alkaline solubilization and acid precipitation, aiming to decipher how extraction pH (7-11) influenced extractability, purity and recovery rate, composition, multi-length scale structure, and gelling properties of quinoa protein isolate (QPI). The results showed that protein extractability increased from 39 to 58% with the increment of pH from 7 to 11 whereas protein purity decreased from 89 to 82%. At pH 7-11, extraction suspensions and QPI showed the similar major bands in SDS-PAGE with more minor ones (e.g., protein fractions at > 55 or 25-37 kDa) in suspensions. Extraction pH had limited effect on the secondary structure of QPI. In contrast, the higher-order structures of QPI were significantly affected, e.g., (1) emission maximum wavelength of intrinsic fluorescence increased with extraction pH; (2) surface hydrophobicity and the absolute value of zeta-potential increased with increasing extraction pH from 7 to 9, and then markedly decreased; (3) the particle size decreased to the lowest value at pH 9 and then increased to the highest value at pH 11; and (4) denaturation temperature of QPI had a large decrease with increasing extraction pH from 7/8 to 9/10. Besides, heat-set QPI gels were formed by loosely-connected protein aggregates, which were strengthened with increasing extraction pH. This study would provide fundamental data for industrial production of quinoa protein with desired quality.

Changes in Soil Microbial Community during Permafrost Collapse Process on the Northeast Qinghai-Tibetan Plateau, China

Changes in Soil Microbial Community during Permafrost Collapse Process on the Northeast Qinghai-Tibetan Plateau, China

Quantifying impact of climatic and anthropogenic factors on runoff in the source region of Alpine River in northeast Qinghai-Tibetan Plateau

Study regionThe Datong River source region in the Northeast Qinghai-Tibetan Plateau Study focusClimate change and anthropogenic factors are the most important factors influencing runoff. Land use/land cover (LULC) is an important anthropogenic factor that has a significant impact on runoff changes. Quantifying runoff variation characteristics and determining the effect of changes in climate and LULC on runoff is important for water resource management and application. The mathematical statistics analysis and soil and water assessment tool (SWAT) were combined to perform a comprehensive analysis of runoff based on meteorological and hydrological data from the Datong River source area, and the effect of changes in climate and LULC on runoff was quantitatively calculated. New hydrological insights for the regionThe results indicate that under the warm and humid climate, there was a slight change in the inter-annual runoff, while the distribution of runoff within the year was uneven due to the control of climate factors. Climate exhibited a positive driving effect on runoff, while LULC reduced the runoff and contributed 125% and − 25%, respectively, to the change in the runoff. Rainfall is the most important climatic factor influencing runoff change. It is recommended that the flood tragedy induced by short periods of high rainfall be taken into account during the process of water resource management in the basin.

Multi-scenario simulation and optimization control of ecological security based on GeoSOS-FLUS model in ecological fragile area in northeast Qinghai-Tibet Plateau, China

Under the dual influence of climate change and human activities, the structure and function of the Qinghai-Tibet Plateau ecosystem have undergone profound changes, and its ecological security has been a frequent focus of academic attention. The calculation of the ecological security bottom line (ESBL) is an essential step in the study of ecological security. However, the current calculation of the ESBL in the ecologically fragile areas of the Qinghai-Tibet Plateau (QTPEFA) has been carried out only from the perspective of supply, and research from the perspective of demand has been largely ignored. Therefore, taking Qinghai Province as study case, this paper exploratively calculated the ESBL from the perspective of supply and demand in combination with food security standards. Simulation of future trends in land-use change and ecosystem service value (ESV) evolution based on GeoSOS-FLUS under four scenarios, i.e., natural development (ND), ecological protection (EP), cultivated land protection (CLP) and dual protection (DP), we explored which protection measures move the ESV closer to the demand ecological security bottom line (DESBL) to provide reasonable suggestions for eco-protection policies. The results showed that: (1) The overall ESV in Qinghai Province showed a continuous increase during the study period, but the change of cultivated land led to different degrees of ESV loss. (2) The ESBL of both supply and demand in Qinghai Province were 6003.41 hundred million and 13132.46 hundred million, respectively. At present, the actual ESV of Qinghai Province is higher than the supply ecological security bottom line (SESBL) but far below the DESBL. (3) Under the four scenarios, the ESV under the DP scenario was closest to the DESBL and provided relatively more food. The DP scenario was most conducive to balancing ecological security and food security in Qinghai Province. This paper provides a new paradigm for measuring the ESBL and provides a scientific basis for optimizing ecological protection policies in the QTPEFA by comparing the results of multi-scenario simulation with the bottom line.

Estimation of aerosol and cloud radiative effects on terrestrial net primary productivity over northeast Qinghai-Tibet plateau

Processes of plant growth are affected by solar radiation reaching the surface, which is regulated by atmospheric components such as aerosols and clouds. However, there are still large uncertainties in evaluating the impact of aerosol radiative effects (ARE) and cloud radiative effects (CRE) on ecosystems. This study estimated the ARE and CRE on vegetation productivity from 2001 to 2020 over the Northeast Qinghai-Tibet Plateau (QTP) based on MODIS satellite data coupled with the validated Radiative Transfer model (RTM) libRadtran and CASA (Carnegie-Ames-Stanford Approach)model. The results showed that both ARE and CRE have restrained vegetation growth in the last 20 years. The net primary productivity (NPP) of vegetation attenuation by ARE was strongest in summer with an increase of temperature and humidity which caused enhanced air particle transformation and hygroscopic growth, followed by spring and autumn, which were extremely affected by dust, and NPP attenuation by ARE was weakest in winter, accounting for 5.2% of the annual NPP. CRE plays an attenuating role on NPP with increasing cloudiness. The ARE reduced NPP by 18.8 g C/m2/yr, and CRE reduced NPP by 406.9 g C/m2/yr. NPP attenuation by CRE was more than ten times that of NPP attenuation by ARE, which indicated that the CRE has a much stronger weakening of NPP than ARE. The area where the trend of NPP at all-sky conditions increases/decreases had a good match with the areas where the trend of NPP by CRE increases/decreases with R2 being 0.89, indicating that CRE plays a dominant role in attenuating NPP. The increase in NPP is mainly attributed to the decrease in NPP attenuation by CRE over the past two decades. The study results could help to comprehensively understand the ARE and CRE on the terrestrial carbon cycle, and to further access and analyze vegetation ecosystem conditions.

Composition, Distribution, and Source Apportionment of Organochlorine Pesticides (OCPs) in Soil of a Chemical Industrial Park and its Surrounding in the Northeast of Qinghai-Tibet Plateau

Composition, Distribution, and Source Apportionment of Organochlorine Pesticides (OCPs) in Soil of a Chemical Industrial Park and its Surrounding in the Northeast of Qinghai-Tibet Plateau

Genomic divergence between two sister Medicago species triggered by the Quaternary climatic oscillations in the Qinghai-Tibet Plateau and northern China.

Speciation is a central topic in evolutionary biology. However, it remains poorly understood of how genomic divergence originated and accumulatedin the face of gene flow during ecological adaptation. Closely related species that have adapted to distinct environments but inhabit some overlapping ranges provide an ideal system to evaluate this issue.Here, we combine population genomics and species distribution models (SDMs) to examine genomic divergences between two sister species, Medicago ruthenicaand M. archiducis-nicolai, that occur in northern China and the northeast Qinghai-Tibet Plateau (QTP), respectively, with overlapping distribution in the border of the two regions.Medicago ruthenicaand M. archiducis-nicolai are well-delimited based on population genomic data, although hybrids exist in sympatric sampling locations. Coalescent simulations and SDMs suggest that the two species diverged from each other in the Quaternary but have been in continuous contact with gene flow occurring between the two species ever since. We also discovered positive selection signatures associated with genes both outside and within genomic islands in both species that are likely involved in adaptations to arid and high-altitude environments. Our findings provide insights into how natural selection and climatic changes in the Quaternary initiated and maintained interspecific divergence of the two sister species.

Assessing the variations of evapotranspiration and its environmental controls over a subalpine wetland valley in China

Dynamics in long-term evapotranspiration (ET) and its controlling variables are essential for understanding how a high-altitude wetlands ecosystem responds to climate change. The rising temperature is expected to agitate the regional hydrological cycle and water balance, particularly in the subalpine wetland valley of Jiuzhaigou, located in the transition zone between the northeast Qinghai-Tibet Plateau and the Sichuan Basin, Southwest China. Here, we used growing season multi-year (2013–2021) Bowen ratio data to assess the variability in ET and its key controlling parameters at different timescales in Jiuzhaigou valley. This study also explored the ratio of ET to precipitation (P). The wetland daily mean ET varied from 0.06 to 6.77 mm d−1, with a mean value of 2.64 mm d−1 for the nine years. Fluctuations in daily ET were primarily driven by available energy (net radiation, Rn), explaining 86 % of the variation. Seasonal patterns in ET were largely similar to environmental parameters, i.e., Rn, air temperature (Ta), and vapor pressure deficit (VPD), peaking in August with an interannual monthly mean value of 3.48 mm d−1. Interannual monthly mean ET had a strong positive linear relationship with Rn, Ta, and VPD, while there was no significant correlation with P on a growing season basis. Furthermore, monthly ET was shown to be regulated by Ta largely in high-temperature months and minimally in low-temperature months. The growing season ET varied interannually, and the ET to P ratio (i.e., ET/P) ranged between 0.52 and 1.16. Interannual variation in annual ET was controlled by Ta and P, which individually explained 73 and 61 % of the variation, respectively. The multiple regression model indicated that Ta and P together elucidated 92 % of the variation in annual ET. The increased sensitivity (e.g., regression slopes) of ET to P over 2014–2021 indicates that ET consumed most of P, which leads to decreasing runoff and streams drying up. This study clarifies the temporal dynamics in ET for wetlands and its environmental controls at multiple timescales. It is demonstrated that the proportion of ET could increase in response to increasing temperature without an associated increase in P, affecting local water balance. These results could potentially contribute to sustainable water management in high-altitude wetlands and environmental planning under future climate change.

Miocene Equisetum tubers from the Wulan Basin, Northeast Qinghai-Tibetan Plateau and their paleoecological significance

Equisetum fossils are often reported from the Cenozoic strata in the Northern Hemisphere, but their occurrence in the Qinghai-Tibetan Plateau (QTP) region is scarce. In this investigation, two new species of tuber fossils of Equisetum — Equisetum wulanense Zhang and Xie, n. sp. and Equisetum kekeense Zhang and Xie, n. sp. from the Miocene Youshashan Formation of the Wulan Basin, Qinghai Province are reported. The extant Equisetum plants are usually living in wet habitats. Therefore, fossil species, E. wulanense and E. kekeense, were likely to live in moist environments during Miocene too. The discovery of E. wulanense and E. kekeense in the late Middle Miocene (∼13.4 Ma) indicates that the local climate of the Wulan Basin was more favorable during this period. This new finding confirmed the previous view that the Neogene aridification in the northern QTP was varying: the climate in the Early Miocene and the Middle Miocene were relatively warm and humid and then the climate gradually became colder and drier since the Late Miocene. It is widely accepted that the uplift of the QTP intensified the trend of cooling and drying since the Late Miocene, and eventually formed a cold and dry climate pattern in the northeast margin of the QTP. The discovery of Equisetum fossils in this investigation improved our understanding on the Cenozoic diversity of Equisetum plants in the northern QTP, as well as on the paleoecological environments of the Wulan Basin in Miocene.

Natural driving mechanism and trade-off and synergy analysis of the spatiotemporal dynamics of multiple typical ecosystem services in Northeast Qinghai-Tibet Plateau

Research on the natural driving mechanism and trade-offs and synergies of ecosystem services (ES) is a prerequisite for the implementation of scientific integrated ecosystem management, especially in ecologically fragile alpine ecological barrier regions. This study mainly studies the spatiotemporal dynamics and natural driving mechanism of water yield (WY), soil conservation (SC), windbreak and sand fixation (WS) and carbon sequestration (CS) in the northeast of the Qinghai-Tibet Plateau, identifies the trade-off and synergy features between ES in horizontal space. The results showed that the distribution of four ES presents different geographical spatial patterns, and an obvious increasing trend during the study period. Seven natural factors (precipitation, temperature, windspeed, etc.) can explain 38.1～47.0% of the spatiotemporal dynamics of ES in 2000, 2010 and 2020. Vegetation characteristics and elevation are the main explanatory variables controlling ES spatial pattern with the total contribution rate of 29.3% in 2000 and 26.5% in 2010. Temperature and elevation are the two most critical natural factors affecting ES, with the contribution ratio of 29.9% in 2020. The contribution of single nature factor on each ES pattern is different in the same year, and show interannual changes in different year. The contributions of wind speed, precipitation and slope to SC are uncertain, and the effect of temperature on CS is nonlinear. The trade-off and synergy cluster areas are mostly agglomerated and embedded in the compatibility region, with the characteristics of regional differentiation. The trade-offs and synergies between ES generally present the characteristics of interannual fluctuation, except WY-SC and WS-CS, which show a weakening trend in 2000, 2010 and 2020. Based on the above findings, we further discussed the complex trade-off and synergy relationships of ES, and the results provide scientific support for sustainable development by creating win–win scenarios under future climate change trends.

Comprehensive efficiency evaluation of wastewater treatment plants in northeast Qinghai–Tibet Plateau using slack–based data envelopment analysis

Comprehensive efficiency analysis of wastewater treatment plants (WWPTs) in the alpine region with harsh environment and poor techniques as well as managing experience could provide targeted and effective improvement evidences for local wastewater treatment industry and help to improve the water quality of downstream reaches. In this paper, slack–based data envelopment analysis (SBM–DEA) was adopted to assess the operating efficiencies of WWPTs in northeast Qinghai–Tibet Plateau (QTP). Results showed that the average efficiency score for all WWPTs was 0.608, and 32.5% of WWPTs were efficient. Some WWPTs had large improvement potentials in operating costs and pollutant removal rates. Lowering expenditures and promoting facility construction for WWPTs to overcome the climate difficulties and improve management level was necessary according to their improvement potentials. In addition, the relative importance of the quantitative influential factors to efficiencies scores calculated by random forest regression (RFR) indicated that design capacity and temperature were important quantitative factors affecting the performance of WWPTs. Furthermore, geographical location and design capacity also had significant influence on the comprehensive efficiency of WWPTs verified by Kruskal–Wallis test. Our results highlight the importance of facilities upgrading, scientific management for WWPTs. And the relative improvement suggestions on overcoming the high and cold environment should also be considered for the efficient operations of WWTPs as well as the protection the aquatic environment.

Combining phylogeography and landscape genetics reveals genetic variation and distribution patterns of Stipa breviflora populations

• Stipa. breviflora originated on the northeastern QTP and the eastern Helan mountains. • S. breviflora originated in the late Miocene. • The genetic differentiation of S. breviflora was mainly caused by IBD. Historical and contemporary microevolutionary processes influence the extent and structure of genetic variation. Combining phylogeography and landscape genetics is an important approach for delineating the formation mechanisms about the patterns of genetic structures. Grassland ecosystems comprise approximately one-third of Earth's vegetative cover. The spatial distribution of genetic variations derived from dominant plant species in steppes is helpful to understand the origin and evolution of this kind of vegetation. In this paper, we took Stipa breviflora , a dominant species of desert steppe, as an example, and conducted the research on both chloroplast DNA sequences and microsatellite loci of populations. The results of analyzing haplotype and microsatellite diversity revealed that S. breviflora most probably originated from the region in eastern Helan Mountains and northeast of Qinghai-Tibet Plateau (QTP) during the late Miocene. The genetic variation distribution of the species was in accordance with the core-periphery hypothesis (CPH), i.e., populations located at the periphery of a species’ range should have lower levels of genetic variation than those at the center of the range. Paleoclimatic fluctuations contributed to haplotype evolution, while geographical distance played an important role in driving contemporary genetic differentiation. Our findings highlight the complexity of intraspecific evolution and clarify the biogeographical history of desert steppes based on molecular signals.

Formation and variations of dew and hoarfrost in the Hulu Catchment on Northeast Qinghai-Tibet Plateau, China

Study regionThe Hulu Catchment on Northeast Qinghai-Tibet Plateau, China Study focusDew and hoarfrost (DH) are prominent components of the Non-Precipitation Water Inputs in arid and semi-arid regions, but research into them is mostly neglected in alpine regions. To understand the formation and variations of DH, as well as whether DH has a significant impact on the water balance and ecosystem, a field measurement experiment of dew was conducted in the Hulu Catchment. Meanwhile, the amount, duration, and frequency of DH at different elevations in the Hulu Catchment from 2016 to 2020 were estimated using the Penman equation. New hydrological insights for the regionDH was common weather phenomenon in the Hulu Catchment, with small interannual and large monthly variations in amount, duration, and frequency. DH showed significant seasonal pattern and elevation dependence, which depending on the seasonal pattern and elevation dependence of meteorological factors. The mean annual amount of DH ranged from 3 mm to 33 mm, contributing 0.3–7.3% of precipitation, indicating that DH was not a critical component of water balance. Nevertheless, DH was ecologically important in replenishing surface soil water deficits and mitigating diurnal fluctuations in surface temperature, protecting vegetation and microorganisms from water and temperature stress in alpine regions. This study has important implications for understanding the energy transfer, water cycle and ecosystem operation in alpine regions.

Seasonal Variation in Soil and Herbage CO2 Efflux for a Sheep-Grazed Alpine Meadow on the North-East Qinghai-Tibetan Plateau and Estimated Net Annual CO2 Exchange.

The Qinghai-Tibetan Plateau is a vast geographic area currently subject to climate warming. Improved knowledge of the CO2 respiration dynamics of the Plateau alpine meadows and of the impact of grazing on CO2 fluxes is highly desirable. Such information will assist land use planning. We measured soil and vegetation CO2 efflux of alpine meadows using a closed chamber technique over diurnal cycles in winter, spring and summer. The annual, combined soil and plant respiration on ungrazed plots was 28.0 t CO2 ha−1 a−1, of which 3.7 t ha−1 a−1occurred in winter, when plant respiration was undetectable. This suggests winter respiration was driven mainly by microbial oxidation of soil organic matter. The winter respiration observed in this study was sufficient to offset the growing season CO2 sink reported for similar alpine meadows in other studies. Grazing increased herbage respiration in summer, presumably through stimulation of gross photosynthesis. From limited herbage production data, we estimate the sustainable yield of these meadows for grazing purposes to be about 500 kg herbage dry matter ha−1 a−1. Addition of photosynthesis data and understanding of factors affecting soil carbon sequestration to more precisely determine the CO2 balance of these grasslands is recommended.