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Microplastics (MPs) become ubiquitous in soil and are an environmental and public health concern worldwide. However, the status of MPs in natural and farmland soils in remote areas remains poorly understood. In this study, we investigated the characteristics of MPs in natural and farmland soils along two transects in the Qilian Mountains of the northern Tibetan Plateau. The average abundance of MPs in natural and farmland soils was 29,778 and 56,123 items kg−1, respectively, with a detection size range of 10–1000 μm. MPs in the size range of 10–100 μm accounted for 84.1% of particles detected. Among the 21 polymers detected, polyethylene dominated in both farmland and natural soils. The shape of MPs was dominated by fragments (95.8%), followed by fibers (3.8%) and beads (0.4%). The abundance of MPs was positively correlated with increasing altitude in natural soils. There was no significant correlation between the abundance of MPs and soil physicochemical properties due to the narrow range of values of soil physicochemical properties. With the growing concern regarding MPs pollution, research on the status of MPs in high altitude and remote areas is critical to understanding their global cycle. [ABSTRACT FROM AUTHOR]

Granite genesis is crucial to understanding the evolution of continental crust, yet many concerns about granite genesis remain not well answered, such as whether I-type granite contains metasedimentary components, what controls granite compositional diversity, and how granitic plutons are constructed. To explore these issues, we conducted a detailed study on the two-mica plagiogranite, tonalite, and biotite plagiogranite units of the Wujinxia composite pluton in the eastern Qilian orogen, NE Tibetan Plateau. These units comprise two-mica plagiogranite, tonalite (with diorite enclave), and biotite plagiogranite. Zircon U–Pb data reveal that three granitic units formed at ~ 487 Ma, ~ 464 Ma, and ~ 430 Ma, respectively. Magmatic and xenocrystic garnet were identified from the tonalite and biotite plagiogranite, respectively. The two-mica plagiogranite, tonalite, and biotite plagiogranite all belong to low-K series rocks (K2O/Na2O = 0.10–0.26), and were derived from deep crustal sources mainly consisting of juvenile mafic rocks, with involvement of minor metasedimentary rocks in the magma sources of the two-mica plagiogranite and tonalite. The diorite enclave within the tonalite was probably derived from an enriched mantle-derived basaltic magma. Mineral compositions, thermobarometric calculations, and whole-rock geochemical data indicate that the low-K intrusive units of the Wujinxia composite pluton resulted from multiple magmatic systems at different depths. The results suggest that I-type granites can contain metasedimentary components by partial melting of a mixed crustal source, and high-Mn content helps the preservation of high-Ca garnet within such rocks. For a composite pluton spanning a large compositional variation, its compositional diversity is jointly controlled by magma source composition, melting condition and thermal evolution of individual magma pulses, and the resulted assembly style during pluton construction. [ABSTRACT FROM AUTHOR]

The South Asian summer monsoon (SASM) is a significant monsoon system that exerts a profound impact on climate and human livelihoods. According to 38 models from the Coupled Model Intercomparison Project Phase 6, the SASM circulation is projected to weaken significantly under global warming as seen in the weakened low-level westerly wind over the northern tropical Indian Ocean; however, the associated climate dynamics is still under debate. Here, we identify that the weakened low-level westerly wind is closely related to the enhanced latent heating over the Tibetan Plateau (TP), which corresponds with increased summer precipitation in the future. The intensified TP latent heating triggers an anomalous meridional circulation with ascending motions over the plateau and descending motions to the south, leading to an anomalous low-level anticyclone over the northern tropical Indian Ocean. This anticyclone greatly weakens the prevailing low-level westerlies of the SASM through easterly anomalies at the anticyclone's southern flank. Moisture budget analysis further reveals that increased atmospheric water vapor, rather than the vertical dynamic component, makes the largest contribution to the increased precipitation over the TP. This result confirms that the enhanced TP latent heating is a driver of atmospheric circulation change and contributes to weakening the SASM circulation. [ABSTRACT FROM AUTHOR]

As an essential moisture transport channel over the Tibetan Plateau (TP), accurate simulation of precipitation over the southeastern TP (SETP) is crucial for downstream moisture transport and water resource assessment. To improve SETP's precipitation simulation accuracy, a Turbulent Orographic Form Drag (TOFD) scheme, which represents the TOFD effect of subgrid orography on model grids, is employed. The impact of TOFD on cloud and precipitation during the summer monsoon over the SETP is investigated from dynamical and cloud microphysical perspectives. Through comparison with ground observations and satellite precipitation data, TOFD reduces the simulated precipitation bias. Despite reducing moisture transport, TOFD enhances low-level convergence and high-level divergence by influencing the low-level wind, thereby strengthening updraft and cloud and precipitation processes before the slope of SETP. TOFD also increases total precipitation before the slope by promoting heavy precipitation and reducing weak precipitation. However, TOFD diminishes the updraft and cloud and precipitation processes over the slope of SETP by influencing low-level wind. The reduced moisture transport by TOFD leads to decreased precipitation over the slope. Additionally, TOFD reduces total precipitation over the slope by promoting weak precipitation and reducing heavy precipitation. Furthermore, the impact mechanism of TOFD on precipitation depends on the wind speed, which is weakened during weak precipitation period with reduced wind speed and enhanced during heavy precipitation period with increased wind speed. These findings enhance the understanding of the complex terrain's influence on cloud and precipitation and provide a basis for improving cloud and precipitation simulation over the SETP. [ABSTRACT FROM AUTHOR]

South Asian summer monsoon (SASM) and westerlies are essential to the precipitation over Tibetan Plateau (TP) by transporting water vapor. Based on the latest reanalysis datasets, we investigate the compound mechanisms of SAMS and westerlies influencing summer precipitation over the TP. The results show that the summer precipitation over the TP is mainly modulated by two meridional Rossby wave trains which are linked to the compound impacts of SASM and westerlies over the TP (TPW). When both the SASM and the TPW are stronger, a cyclone over India and an anticyclone over Southeast Asia could jointly enhance the transport of warm and moist airflow to the TP along its southern boundary. Meanwhile, a cyclonic anomaly over the northwestern TP and an anticyclonic anomaly over the northeastern TP could induce the southward invasion of cold airflow. Consequently, the convergence of warm and cold airflows can result in more summer precipitation over the southern TP. On the contrary, when both the SASM and the TPW are weaker, a reversed pattern of above wave trains is stimulated, leading to more precipitation over the northeastern TP. Besides, with the stronger SASM and the weaker TPW configurated, anomalous moisture convergence (divergence) and ascending (descending) motion are found over the eastern (western) TP, producing more (less) precipitation over the eastern (western). Contrarily, with the weaker SASM and the stronger TPW configurated, the summer precipitation will be increased over the western TP. Overall, the compound impacts of SASM and TPW on the TP summer precipitation are significantly related to the dynamical processes instead of thermodynamic processes. Our results reveal the necessary of considering compound impacts of the SASM and TPW to explain the TP summer precipitation variation. [ABSTRACT FROM AUTHOR]

Accurate initial soil conditions play a crucial role in simulating soil hydrothermal and surface energy fluxes in land surface process modeling. This study emphasized the influence of the initial soil temperature (ST) and soil moisture (SM) conditions on a land surface energy and water simulation in the permafrost region in the Tibetan Plateau (TP) using the Community Land Model version 5.0 (CLM5.0). The results indicate that the default initial schemes for ST and SM in CLM5.0 were simplistic, and inaccurately represented the soil characteristics of permafrost in the TP which led to underestimating ST during the freezing period while overestimating ST and underestimating SLW during the thawing period at the XDT site. Applying the long-term spin-up method to obtain initial soil conditions has only led to limited improvement in simulating soil hydrothermal and surface energy fluxes. The modified initial soil schemes proposed in this study comprehensively incorporate the characteristics of permafrost, which coexists with soil liquid water (SLW), and soil ice (SI) when the ST is below freezing temperature, effectively enhancing the accuracy of the simulated soil hydrothermal and surface energy fluxes. Consequently, the modified initial soil schemes greatly improved upon the results achieved through the long-term spin-up method. Three modified initial soil schemes experiments resulted in a 64%, 88%, and 77% reduction in the average mean bias error (MBE) of ST, and a 13%, 21%, and 19% reduction in the average root-mean-square error (RMSE) of SLW compared to the default simulation results. Also, the average MBE of net radiation was reduced by 7%, 22%, and 21%. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau supplies water to nearly 2 billion people in Asia, but climate change poses threats to its aquatic microbial resources. Here, we construct the Tibetan Plateau Microbial Catalog by sequencing 498 metagenomes from six water ecosystems (saline lakes, freshwater lakes, rivers, hot springs, wetlands and glaciers). Our catalog expands knowledge of regional genomic diversity by presenting 32,355 metagenome-assembled genomes that de-replicated into 10,723 representative genome-based species, of which 88% were unannotated. The catalog contains nearly 300 million non-redundant gene clusters, of which 15% novel, and 73,864 biosynthetic gene clusters, of which 50% novel, thus expanding known functional diversity. Using these data, we investigate the Tibetan Plateau aquatic microbiome's biogeography along a distance of 2,500 km and >5 km in altitude. Microbial compositional similarity and the shared gene count with the Tibetan Plateau microbiome decline along with distance and altitude difference, suggesting a dispersal pattern. The Tibetan Plateau Microbial Catalog stands as a substantial repository for high-altitude aquatic microbiome resources, providing potential for discovering novel lineages and functions, and bridging knowledge gaps in microbiome biogeography. The Tibetan Plateau is the largest plateau in the world and hosts a variety of aquatic ecosystems. Here, the authors present a gene and genome catalogue of Tibetan Plateau aquatic microbiomes, greatly expanding known taxonomic and functional diversity for the region and giving insights into its microbial biogeography. [ABSTRACT FROM AUTHOR]

Tibetan Plateau (TP) is known as the water tower of Asia, and glaciers are solid reservoirs that can regulate the amount of water. Black carbon (BC), as one of the important factors accelerating glacier melting, is causing evident environmental effects in snow and ice. However, a systematical summary of the potential sources, analytical methods, distributions, and environmental effects of BC in snow and ice on the TP's glaciers is scarce. Therefore, this study drew upon existing research on snow and ice BC on glaciers of the TP to describe the detection methods and uncertainties associated with them to clarify the concentrations of BC in snow and ice and their climatic effects. The primary detection methods are the optical method, the thermal–optical method, the thermochemical method, and the single-particle soot photometer method. However, few studies have systematically compared the results of BC and this study found that concentrations of BC in different types of snow and ice varied by 1–3 orders of magnitude, which drastically affected the regional hydrologic process by potentially accelerating the ablation of glaciers by approximately 15% and reducing the duration of snow accumulation by 3–4 days. In general, results obtained from the various testing methods differ drastically, which limited the systematical discussion. Accordingly, a universal standard for the sampling and measurement should be considered in the future work, which will be beneficial to facilitate the comparison of the spatiotemporal features and to provide scientific data for the model-simulated climatic effects of BC. [ABSTRACT FROM AUTHOR]

Context: Tibetan alpine ecosystems are among the world's fastest-warming natural systems, and consequently, are expected to undergo dramatic changes in their ecological processes. However, despite the importance of ants in mediating these ecological processes, it remains unclear how they will respond to the rapid climate warming on the Tibetan Plateau. Objectives: In this perspective piece, we aim to establish a baseline understanding of the spatial distribution of ants on the Tibetan Plateau, to evaluate how these ants respond to climate change such as warming at both local and regional scales, and to identify future research avenues that can elucidate the impacts of warming-induced ant expansion. Methods: We first present the results of a long-term climate manipulation experiment on how ants respond to warming in a Tibetan alpine grassland. Next, we evaluated the current and future distribution of ants on the Tibetan Plateau using the MaxEnt model with data compiled from existing field survey of ant species in the region. Finally, we synthesize published studies to review the ecosystem functions in which ants are involved on the Tibetan Plateau and identify gaps in current research. Results: From our field warming experiment, we found that ant abundance significantly increased from 2017 to 2022. For our region-scale analysis, we found that the distribution of ants on the Tibetan Plateau will expand with future warming. Lastly, we identify a few key gaps in our knowledge of ants' ecological impacts (e.g., greenhouse gas emissions, trophic network, and the interplay between the different ecosystem properties). Conclusions: Our results suggest that ants are widespread on the Tibetan Plateau, and involved in several important ecosystem processes with significant impacts on soils, plants, microbes and Tibetan faunas. With rapid climate warming, their abundance, and ecological functions will further lead to unknown far-reaching impacts on the health of the ecosystem, food web dynamics, and nutrient cycling of Tibetan alpine ecosystems. We call for more research activities to address critical knowledge gaps that have not been explicitly assessed in this important geographic region. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau contains the highest and largest alpine pasture in the world, which is adapted to the cold and arid climate. It is challenging to understand how the vast alpine grasslands respond to climate change. We aim to test the hypothesis that there is local adaptation in elevational populations of major plant species in Tibetan alpine grasslands, and that the spatiotemporal variations of aboveground biomass (AGB) and species richness (S) can be mainly explained by climate change only when the effect of local adaptation is removed. A 7-year reciprocal transplant experiment was conducted among the distribution center (4950 m), upper (5200 m) and lower (4650 m) limits of alpine Kobresia meadow in central Tibetan Plateau. We observed interannual variations in S and AGB of 5 functional groups and 4 major species, and meteorological factors in each of the three elevations during 2012–2018. Relationships between interannual changes of AGB and climatic factors varied greatly with elevational populations within a species. Elevation of population origin generally had a greater or an equal contribution to interannual variation in AGB of the 4 major species, compared to temperature and precipitation effects. While the effect of local adaptation was removed by calculating differences in AGB and S between elevations of migration and origin, relative changes in AGB and S were mainly explained by precipitation change rather than by temperature change. Our data support the hypothesis, and further provide evidence that the monsoon-adapted alpine grasslands are more sensitive to precipitation change than to warming. [ABSTRACT FROM AUTHOR]

To provide evidence-based medicine references for formulating prevention and control policies in plateau areas, we explore the characteristics of anemia patients in Tibet (the plateau areas of China), especially those located at an altitude above 4500 m. We collected clinical data from 379 Tibetan anemia patients over the age of 18 years. We found those female patients accounted for the majority of Tibetan anemia patients. Almost half of the anemia patients aged from 28 to 47 years. The percentage of severe anemia and extremely severe anemia was 45.4% and 2.4%, respectively. 88.7% of patients are engaged in agriculture and animal husbandry, and 81.5% of patients just graduated from primary school or below. The most common causes of anemia were nutritional anemia, especially iron-deficiency anemia. At high-altitude localities, folic acid-deficiency anemia needs more attention. Overall, this study showed that altitude influences the incidence, severity, and cause of anemia. Peasants and herdsmen, low education levels, young and middle-aged women, and nutrition status should be paid attention to in future anemia control. [ABSTRACT FROM AUTHOR]

Desertification is a process of land degradation embodied in soil water reduction, soil deterioration and vegetation degradation. As an important factor to evaluate the desertification degree, the water content of shallow soil will infiltrate downward when permafrost degrades on the Qinghai-Tibet Plateau (QTP). With the development of transportation facilities on the QTP, embankment construction, which will directly change the surface cover and reduces the water content of shallow soil by degrading the permafrost. In this study, an embankment construction in the permafrost region of the QTP was selected and a hydro-thermo-vapor coupling model for the embankment-permafrost system was established. The mechanism and process of desertification caused by permafrost degradation were analyzed by the variations of geotemperature and soil water. The results show that: (1) embankment construction has increased the heat flowing into the ground, warmed the underlying permafrost and deepened the permafrost table by more than 10 m during 50 years. (2) Accompanied with the permafrost degradation, the shallow soil water migrates downward and accumulates near the deepening permafrost table, showing a funnel-shaped distribution. The average water content of shallow soil under the changed surface has decreased by 5–6% during 50 years, indicating the intensification of desertification. (3) Desertification and permafrost degradation on the QTP is interconnected by the redistribution of soil water. Desertification and permafrost degradation are the mutual promotion process on the QTP. [ABSTRACT FROM AUTHOR]

Terrestrial ecosystem water use efficiency (WUE) is an important indicator for coupling plant photosynthesis and transpiration, and is also a key factor linking the carbon and water cycles between the land and atmosphere. However, under the combination of climate change and human intervention, the change in WUE is still unclear, especially on the Tibetan Plateau (TP). Therefore, satellite remote sensing data and process-based terrestrial biosphere models (TBMs) are used in this study to investigate the spatiotemporal variations of WUE over the TP from 2001 to 2010. Then, the effects of land use and land cover change (LULCC) and CO2 fertilization on WUE from 1981–2010 are assessed using TBMs. Results show that climate change is the leading contributor to the change in WUE on the TP, and temperature is the most important factor. LULCC makes a negative contribution to WUE (−20.63%), which is greater than the positive contribution of CO2 fertilization (11.65%). In addition, CO2 fertilization can effectively improve ecosystem resilience on the TP. On the northwest plateau, the effects of LULCC and CO2 fertilization on WUE are more pronounced during the driest years than the annual average. These findings can help researchers understand the response of WUE to climate change and human activity and the coupling of the carbon and water cycles over the TP. [ABSTRACT FROM AUTHOR]

A significant drying tendency over the southern slope of the Tibetan Plateau (SSTP) in summer (especially in July–September) during 1980–2018 is identified in this study. Moisture budget analysis reveals that the drying tendency is dominated by a decreased vertical moisture advection due to weakened upward motion, which is mainly resulted from an anticyclonic trend appeared over the northeastern TP. This anomalous anticyclone can weaken the upper-tropospheric divergence pumping over the SSTP. In addition, moist static energy diagnosis indicates that the southern branch of the anomalous anticyclone advects low moist enthalpy air into the SSTP, which also suppresses local upward motion and convection. Moreover, the anticyclonic trend over the northeastern TP is found not a local phenomenon, but is rather associated with the large-scale atmospheric change in the middle latitudes that shows a circumglobal teleconnection (CGT)-like pattern. Our results highlight that the long-term CGT-like trend of atmospheric circulation plays a crucial role in triggering the drying tendency over the SSTP in recent decades. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) has unique atmospheric dynamics and thermal structures that originate from its giant terrain and complex climate. High vertical-resolution thermal radiosondes were launched near the central (Lhasa, 91°06′E, 29°36′N, 3670 m above sea level (ASL)) and marginal (Da Qaidam, 95°21′E, 37°51′N, 3180 m ASL) areas of the TP during the summers of 2018 and 2020, respectively. Atmospheric turbulence parameters were calculated, and the characteristics of the atmospheric turbulent vertical structure at sunset in these two areas were analyzed and compared. Affected by TP thermal forcing and stably controlled by the summer monsoon anticyclone, the atmospheric refractive index structure constant (Cn2) tended to increase and then decrease with increasing height, reaching a maximum at the tropopause (∼18 km ASL) at the Lhasa site. Although Cn2 at the Da Qaidam site also tended to increase at the tropopause, the position of the strong turbulent band (STB) (5–7 km ASL) was below the tropopause height corresponding to the potential temperature lapse rate minimum. The vertical distribution of Cn2 at the two sites, particularly regarding the position of the STB, was highly correlated with the atmospheric stability (Ri) and the thermal mixing scale (LT). The significant correlations among the three parameters (STB, Ri, and LT) indicated that the strong fluctuations in temperature caused by thermal mixing were the dominant factor causing the Ri to be less than its critical value of 0.25. Moreover, the suppression strength involving the upward transport of the heat sources was the main reason for the different turbulent vertical structures and STB positions at the two sites. The zonal mean thermodynamic and dynamical fields derived from the reanalysis data also showed a height difference in the heat sources transported to the troposphere at the two sites. In the marginal TP, the material and energy in the lower troposphere were transported by the turbulent atmosphere upward along the slope of the mountain and converged at the central TP (28°N–35°N) with strong thermal forcing up to the tropopause. In the STB of the Lhasa site, the turbulent dissipation rate and eddy diffusion coefficient increased sharply, indicating that the turbulent atmosphere in this central site was highly diffused, and the small-scale turbulence transported the material and energy upward. [ABSTRACT FROM AUTHOR]

Background and aims: Dissolved organic nitrogen (DON) has been increasingly recognized as a crucial component of the terrestrial nitrogen (N) cycle that regulates the ecosystem feedback to climate change. Yet, little information is available about the factors that control soil DON in the alpine ecosystems of the Tibetan Plateau, a region that is extremely sensitive to climate change. Methods: Here, we examined the relationship between DON and climate, plant, and soil attributes along a precipitation gradient in five alpine ecosystems (alpine wetland, alpine meadow, alpine shrub, alpine steppe, and alpine desert) across 20 sites that were up to 4000 km apart on the Tibetan Plateau. Results: Results showed that soil DON concentration varied significantly across these alpine ecosystems, and had a positive relationship with mean annual precipitation. Belowground biomass, soil moisture, micro biomass carbon (MBC), and soil total phosphorus (TP) explained 84% of the variation in DON concentrations. The percentage of DON in soil total dissolved N (TDN) varied with vegetation type, with the lowest percentage observed in the alpine meadow (52%) and the highest in the alpine desert (77%), indicating the slow turnover of DON into inorganic N in systems with low litter input and microbial activity. Conclusions: Precipitation and plant biomass input determine the concentration and turnover of soil DON on the Tibetan Plateau. A warmer and wetter climate that has been predicted for the Tibetan grasslands may lead to a larger and more active DON pool. [ABSTRACT FROM AUTHOR]

Gymnocypris namensis, the only commercial fish in Namtso Lake of Tibet in China, is rated as nearly threatened species in the Red List of China's Vertebrates. As one of the highest-altitude schizothorax fish in China, G. namensis has strong adaptability to the plateau harsh environment. Although being an indigenous economic fish with high value in research, the biological characterization, genetic diversity, and plateau adaptability of G. namensis are still unclear. Here, we used Pacific Biosciences single molecular real time long read sequencing technology to generate full-length transcripts of G. namensis. Sequences clustering analysis and error correction with Illumina-produced short reads to obtain 319,044 polished isoforms. After removing redundant reads, 125,396 non-redundant isoforms were obtained. Among all transcripts, 103,286 were annotated to public databases. Natural selection has acted on 42 genes for G. namensis, which were enriched on the functions of mismatch repair and Glutathione metabolism. Total 89,736 open reading frames, 95,947 microsatellites, and 21,360 long non-coding RNAs were identified across all transcripts. This is the first study of transcriptome in G. namensis by using PacBio Iso-seq. The acquisition of full-length transcript isoforms might accelerate the transcriptome research of G. namensis and provide basis for further research. [ABSTRACT FROM AUTHOR]

Soil temperature, an important indicator of climate change, has rarely explored due to scarce observations, especially in the Tibetan Plateau (TP) area. In this study, changes observed in five meteorological variables obtained from the TP between 1960 and 2014 were investigated using two non-parametric methods, the modified Mann-Kendall test and Sen's slope estimator method. Analysis of annual series from 1960 to 2014 has shown that surface (0 cm), shallow (5-20 cm), deep (40-320 cm) soil temperatures (ST), mean air temperature (AT), and precipitation (P) increased with rates of 0.47 °C/decade, 0.36 °C/decade, 0.36 °C/decade, 0.35 °C/decade, and 7.36 mm/decade, respectively, while maximum frozen soil depth (MFD) as well as snow cover depth (MSD) decreased with rates of 5.58 and 0.07 cm/decade. Trends were significant at 99 or 95% confidence level for the variables, with the exception of P and MSD. More impressive rate of the ST at each level than the AT indicates the clear response of soil to climate warming on a regional scale. Monthly changes observed in surface ST in the past decades were consistent with those of AT, indicating a central place of AT in the soil warming. In addition, with the exception of MFD, regional scale increasing trend of P as well as the decreasing MSD also shed light on the mechanisms driving soil trends. Significant negative-dominated correlation coefficients (α = 0.05) between ST and MSD indicate the decreasing MSD trends in TP were attributable to increasing ST, especially in surface layer. Owing to the frozen ground, the relationship between ST and P is complicated in the area. Higher P also induced higher ST, while the inhibition of freeze and thaw process on the ST in summer. With the increasing AT, P accompanied with the decreasing MFD, MSD should be the major factors induced the conspicuous soil warming of the TP in the past decades. [ABSTRACT FROM AUTHOR]

Thermal infrared remote sensing technology based on unmanned aerial vehicle (UAV) was applied to estimate the spatial distribution of ground surface temperatures on permafrost slopes and evaluate the thermal influence of nearby engineering infrastructure. This paper presents a method that uses a miniature UAV with a thermal infrared sensor to collect thermal images with high temporal-spatial resolution. Moreover, spatial analysis is used to effectively evaluate the relationship between engineering infrastructure and permafrost slopes in the Qinghai-Tibet Engineering Corridor (QTEC), China. To test the method, aerial measurements were collected from 11:00 to 17:00 in July and August of 2017 at two permafrost slopes along the QTEC, where the Qinghai-Tibet Highway (QTH), Qinghai-Tibet Railway (QTR), and electric towers were built on permafrost slopes. The differences of ground surface temperature between the highway and the surrounding soil were largest at 11:00 and 17:00; the differences were smaller at noon to approximately 15:00 when the difference was minimal, and the differences began to increase after 15:00. The distances of the thermal influence of the highway, railway, and electric towers on the surrounding permafrost slopes are approximately 12-14, 8-10, and 2-4 m, respectively. The results indicate that the degree of influence of engineering structures on permafrost slopes is as follows: QTH > QTR > electric towers. This study is the first to use UAV-based thermal infrared remote sensing to evaluate the thermal dynamics of permafrost slopes along the QTEC. These results may provide new insights into the future design, construction, and maintenance of engineering structures on permafrost slopes. [ABSTRACT FROM AUTHOR]

Soil temperature changes in cold regions can have great impacts on the land surface energy and water balance, and hence changes in weather and climate, surface and subsurface hydrology and ecosystem. We investigate the spatiotemporal variations of annual soil temperature at depths of 0, 5, 10, 15, 20, and 40 cm during 1983-2013 using observations at 85 stations on the Tibetan Plateau (TP). Our results show that the climatological soil temperatures exhibit a similar spatial pattern among different depths and they are generally higher than surface air temperature at the individual stations. Spatially averaged soil temperature show that the TP has experienced significant warming trends at all six depths during 1983-2013, and the soil at 0-cm depth has the fastest warming rate among all the six layers and the surface air temperature. The first leading mode of joint empirical orthogonal function (EOF) analysis exhibits a spatially prevailing warming pattern across the six depths. This plateau-wide soil warming correlates very well with surface air temperature and sea surface temperature in response to increasing radiative forcing caused by greenhouse gases. The joint EOF2 displays a southeastern-northwestern dipole pattern on the TP in the interannual-decadal variability of soil temperature at all layers, which appears to be related to the warm season precipitation and anomalous atmospheric circulations. The spatial difference of soil warming rates across stations on the TP is associated primarily with the spatial distribution of precipitation (mainly rainfall), with vegetation, snowfall and elevation playing a rather limited role. [ABSTRACT FROM AUTHOR]

To explore the effects of elevated temperature (ET), elevated atmospheric CO2 concentration (EC) and ET plus EC (ETC) on different fractions of soil organic carbon (SOC) is significant for understanding the interactions between SOC and environmental variables. Up to date, little information is available in montane forests of the eastern Qinghai-Tibetan Plateau, which is a key region for studying global climate change especially for high altitude areas. This work applied an automatic gas exchange system to investigate the responses of different fractions of SOC to these factors (ET: + 2.5 °C; EC: + 350 ppm; ETC: + 2.5 °C + 350 ppm) after two and a half years’ treatments. Results showed that both ET and EC significantly increased the average amount of SOC and not-readily oxidizable carbon (NROC), while significantly decreased the readily oxidizable carbon (ROC) in soil. The dramatic contrast between the content of NROC and ROC provided evidence that trees exposed to either ET or EC would employ more labile nutrient to meet their growth demands. Soil microbial biomass carbon (SMBC) was significantly related to the amount of ROC. Unlike ROC, the trends of particulate organic carbon (POC) and mineral-associated organic carbon (MOC) under different treatments were consistent with that of SOC. Under ET, EC and ETC, the alterations of %ROC were more obvious than that of %POC, and positive correlations were observed between SOC, POC, MOC and NROC, with the exception of ROC and SMBC. These results indicated that the biotical and chemical labile components were more sensitive than the physical active fraction of soil organic matter. Meanwhile, the physical protection and chemical recalcitrance effects were important protection mechanisms from the response to global climate change. [ABSTRACT FROM AUTHOR]

The Northern Qaidam Basin is located at the northeastern part of the Qinghai-Tibetan Plateau. It contains very thick Cenozoic terrestrial clastic sediments, which records the formation of the northern Qaidam Basin due to compressional deformation during the Indo-Asian collision. In this paper, we used detrital apatite fission-track thermochronology, including 4 sandstones and 2 conglomerates samples from the Lulehe section, to reveal the Cenozoic evolution of the northern Qaidam Basin. Fission-track dating indicated the source region of the Lulehe section has experienced important cooling and uplifting in the Late Cretaceous (at ~85.1 Ma and ~65 Ma) and the Eocene (~52 Ma), respectively. The AFT age distribution on the section suggested that the provenance of Lulehe section sediments were mainly derived from the south Qilian Shan (Qilian Mountains) and Altun Shan (Altun Mountains), and two significantly provenance changes may occur at 43.4-46.1 Ma and ~37.8 Ma, respectively. The results may have strong constrains on the Cenozoic deformation and tectonic evolution of the northern Qaidam Basin and Qinghai-Tibet Plateau. [ABSTRACT FROM AUTHOR]

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Ecosystem multifunctionality (EMF), the simultaneous provision of multiple ecosystem functions, is often affected by biodiversity and environmental factors. We know little about how the interactions between biodiversity and environmental factors affect EMF. In this case study, a structural equation model was used to clarify climatic and geographic pathways that affect EMF by varying biodiversity in the Tibetan alpine grasslands. In addition to services related to carbon, nitrogen, and water cycling, forage supply, which is related to plant productivity and palatability, was included in the EMF index. The results showed that 72% of the variation in EMF could be explained by biodiversity and other environmental factors. The ratio of palatable richness to all species richness explained 8.3% of the EMF variation. We found that air temperature, elevation, and latitude all affected EMF, but in different ways. Air temperature and elevation impacted the aboveground parts of the ecosystem, which included plant height, aboveground biomass, richness of palatable species, and ratio of palatable richness to all species richness. Latitude affected EMF by varying both aboveground and belowground parts of the ecosystem, which included palatable species richness and belowground biomass. Our results indicated that there are still uncertainties in the biodiversity-EMF relationships related to the variable components of EMF, and climatic and geographic factors. Clarification of pathways that affect EMF using structural equation modeling techniques could elucidate the mechanisms by which environmental changes affect EMF. [ABSTRACT FROM AUTHOR]

Background and aims: Nitrogen (N) limitation leads to intense competition between plants and soil microorganisms for available N. However, it is unclear how grazing affects the acquisition of N by plants and microorganisms. Methods: We conducted short-term N tracer experiments during the growing season (June, early growing season; July, mid-growing season; and September, late growing season) in an alpine grassland on the Tibetan Plateau to investigate the effects of grazing on the acquisition of NO -N, NH -N, and glycine-N by plants and soil microorganisms. Three dominant plant species (one graminoid, Kobresia pygmaea, and two forbs, Potentilla bifurca and Potentilla multifida) were selected for the study. As these species represented >90% of the vegetation, the plant recovery of N reflected competition at the plant community. Results: Grazing decreased the recovery of N by soil microorganisms and plants by 46 and 69%, respectively, indicating that grazing strongly reduced the uptake of N by plants and microorganisms and altered the partitioning of N between them. Significant interactions were found between grazing, season and the different forms of N. In the absence of grazing, plants acquired relatively more N than soil microorganisms for the three forms of N in July and September, whereas the microorganisms obtained relatively more N glycine in July and all three forms of N in September under grazing conditions. Under grazing, the plant root biomass played an important role in controlling plant-microbial N acquisition. Conclusions: Grazing alters the partitioning of inorganic and organic N between plants and soil microorganisms by reducing microbial N recovery to a lesser extent than plant N recovery. This indicates that heterotrophic microorganisms play an important part in N cycling in N-limited ecosystems. [ABSTRACT FROM AUTHOR]

Crustal earthquake focal mechanisms are investigated in the southeastern margin of the Tibetan Plateau, where the Tibetan Plateau and stable South China Block merge. An updated database of focal mechanisms has been compiled by selecting 132 Global Centroid Moment Tensor solutions and by adding the 173 new solutions (3.5 ≤ Ms ≤ 7.4) estimated by waveform inversion in this study. A total of 305 mechanisms are included in this database. These solutions show regionally specific distributions with dominant strike-slip faulting and some normal and reverse faulting. Focal mechanism solutions have also been inverted for the stress tensor orientation to obtain the principal stress axes over the study region. Results show that the horizontal maximum principal σ axes rotate clockwise with a wider range than the geodetically measured surface motion in the east, which is not limited to the Xianshuihe-Xiaojiang fault, but has some overlap with the Zhaotong-Lianfeng fault. Localized normal faulting stress regimes are observed in the Jinshajiang-Litang fault areas and the Baoshan sub-block. The minimum principal axes are oriented with a gradually changing trend from north-south to northwest-southeast, from north to south, indicating diverse compression stress patterns. Significant changes in the crustal stress field after the Wenchuan earthquake are preliminarily observed in the Baoshan sub-block where orientations of two principal axes have changed, and in the Jinggu-Ximeng sub-block areas where the strike-slip faulting stress pattern has transformed to normal faulting. [ABSTRACT FROM AUTHOR]

Knowledge of the spatial distribution of permafrost and the effects of climate on ground temperature are important for land use and infrastructure development on the Qinghai-Tibet Plateau (QTP). Different permafrost models have been developed to simulate the ground temperature and active layer thickness (ALT). In this study, Temperature at Top of Permafrost (TTOP) model, Kudryavtsev model and modified Stefan solution were evaluated against detailed field measurements at four distinct field sites in the Wudaoliang Basin to better understand the applicability of permafrost models. Field data from 2012 to 2014 showed that there were notable differences in observed ground temperatures and ALTs within and among the sites. The TTOP model is relatively simple, however, when driven by averaged input values, it produced more accurate permafrost surface temperature (Tps) than the Kudryavtsev model. The modified Stefan solution resulted in a satisfactory accuracy of 90%, which was better than the Kudryavtsev model for estimating ALTs. The modified Stefan solution had the potential of being applied to climate-change studies in the future. Furthermore, additional field investigations over longer periods focusing on hydrology, which has significant influence on permafrost thaw, are necessary. These efforts should employ advanced measurement techniques to obtain adequate and extensive local parameters that will help improve model accuracy. [ABSTRACT FROM AUTHOR]

The distribution of permafrost-related slope failures along the Qinghai-Tibet Highway from Wuddaoliang to Fenghuoshan correlates with ice content, slope gradient, and ground temperature. Slope failures are of two types. (1) Retrogressive thaw slumps result from icy permafrost being exposed by either man-induced excavation or fluvial-thermal erosion and undercutting of basal slopes. (2) Active-layer-detachment failures are caused by thaw of icy permafrost at the active layer-permafrost interface. After initial failure, active-layer-detachment failures can lead to retrogressive thaw-slumping and localized surficial landslide. Common trigger mechanisms for failure include high summer air temperatures and heavy summer precipitation. A third possible trigger mechanism for slope failure is earthquake occurrence. A geotechnical slope stability analysis was undertaken for an active-layer-detachment failure that had progressed into a retrogressive thaw slump. A safety factor ( F) of 1.24 for the natural slope was determined using in situ tested strength parameters. However, the slope would lose stability when either the groundwater level over the permafrost table exceeded 1.42 m or seismic acceleration reached, or exceeded, 0.03 g. [ABSTRACT FROM AUTHOR]

Background and aims: Understanding the effect of grazing season on net ecosystem CO exchange (NEE) and its components is crucial to predict the feedback of grazing management to climate change. Methods: We estimated NEE, gross primary productivity (GPP) and ecosystem respiration (Re) under different seasonal grazing practices (i.e. no-grazing (NG), warm season grazing (WG) and cold season grazing (CG)) by sheep during the growing seasons from 2008 to 2012 on the Tibetan Plateau. Results: Our results show that the impacts of seasonal grazing on daily GPP, Re and NEE in the alpine meadow ecosystem varied with sampling date and year. Compared with NG and CG, WG significantly reduced average seasonal NEE by 22.7 %, because grazing impact was exacerbated by drought in July in 2010. Soil temperature only explained 19-31 % of the variation in daily GPP, Re and NEE for all grazing treatments. The interannual variabilities of GPP, Re and NEE were mainly determined by root biomass and/or average soil temperature during the growing season. Conclusions: Our results suggest that although WG may decrease sequestration of CO under continuous drought conditions after grazing, it would have little impact on CO sequestration during the growing season under conditions of future warming with greater rainfall in alpine meadows on the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Ten years of ground temperature data (2003-2013) indicate that the long-term thermal regimes within embankments of the Qinghai-Tibet Railway (QTR) vary significantly with different embankment structures. Obvious asymmetries exist in the ground temperature fields within the traditional embankment (TE) and the crushed-rock basement embankment (CRBE). Measurements indicate that the TE and CRBE are not conducive to maintaining thermal stability. In contrast, the ground temperature fields of both the crushed-rock sloped embankment (CRSE) and the U-shaped crushed-rock embankment (UCRE) were symmetrical. However, the UCRE gave better thermal stability than the CRSE because slow warming of deep permafrost was observed under the CRSE. Therefore, the UCRE has the best long-term effect of decreasing ground temperature and improving the symmetry of the temperature field. More generally, it is concluded that construction using the cooling-roadbed principle meets the design requirements for long-term stability of the railway and for train transport speeds of 100 km h. However, temperature differences between the two shoulders, which exist in all embankments shoulders, may cause potential uneven settlement and might require maintenance. [ABSTRACT FROM AUTHOR]

Increased understanding of the response of soil methane (CH) uptake in alpine meadow ecosystems to warming and grazing could reduce uncertainty in estimates of the soil-atmospheric CH budget. To determine the effects of warming and grazing on soil CH uptake at different timescales (that is, daily, monthly, seasonal, and annual), we conducted a controlled warming and grazing experiment [that is, no warming with no grazing (NWNG), no warming with grazing (NWG), warming with no grazing (WNG), and warming with grazing (WG)] in an alpine meadow on the Tibetan plateau from 2006 to 2009. Soil CH uptake was mainly affected by warming and sample date and their interaction. Warming treatment regardless of grazing significantly increased seasonal average CH uptake by 31-39% during the growing season (from May to September) and by 162% during the non-growing season (from October to April next year) in 2007-2008, whereas only WNG increased seasonal average CH uptake by 87-138% compared with NWNG during the non-growing seasons in 2006-2007 and 2008-2009. Warming in WNG and WG increased annual CH uptake by 50-87% compared with NWNG or NWG. Moreover, warming regardless of grazing and warming with grazing (compared with NWNG) significantly increased the contribution to annual uptake of CH uptake during the non-growing season in 2007-2008 and 2008-2009. However, moderate grazing did not significantly influence soil CH uptake, although grazing with warming decreased CH uptake by 43% during the growing season in 2006. Soil moisture explained 16-25% of the CH variation during the growing season, but there was no significant relationship between soil CH uptake and soil moisture during the non-growing season. Our results suggest that more attention should be paid to the stimulating effect of warming on soil CH uptake during the non-growing season due to its greater response to warming and different stimulating mechanisms compared to responses during the growing season in the alpine meadow. [ABSTRACT FROM AUTHOR]

The health of coniferous forests has been attended due to the heavy metal pollution. The accumulation of heavy metals can increase the risk of harmful effects in the future. The monitoring of soil in timberline forests in the east of the Tibetan plateau was performed. Soil samples were collected by laminating sampling. Concentrations of Cd and Pb were analyzed by ICP-MS. Spatial distribution of elements (Cd and Pb) by geostatistical analysis is presented. The concentrations of Pb and Cd between different years (in 1990 and in 2012) also are compared. Results show that Cd and Pb concentrations of soil are much higher in current levels. Cd and Pb inputs of timberline forests present an increasing trend in the last two decades. Such heavy metal monitoring of soil is needed to provide databases so that the next step of this kind would be to evaluate levels of trace metal accumulation, formulate environmental legislation and control strategies of timberline forests in the future. The possible source and influencing factors of Cd and Pb in soil are also discussed. [ABSTRACT FROM AUTHOR]

With recent climatic warming and enhanced human activities, slope failures related to permafrost degradation are widespread along the Qinghai-Tibet Engineering Corridor. Assessment and mapping of the slope failures are necessary to mitigate hazards and plan engineering activities. According to our field investigations, the occurrence of slope failures is mainly controlled by the slope gradient, ground-ice content, permafrost temperatures, surficial deposits, and slope aspect. Modeling conducted in ArcGIS™ was used to produce a slope failure susceptibility map for a representative region along the Qinghai-Tibet Railway from Wudaoliang to Fenghuo Mountain Pass. The study region was divided into four classes based on slope failure susceptibility: (1) unlikely, (2) low, (3) moderate, and (4) high. Areas classified as unlikely accounted for 10.76 % of the study region, while low susceptibility areas comprised 44.51 %. The moderate and high susceptibility zones comprised 21.79 and 22.94 %, respectively. The actual distribution of slope failures in the region was consistent with the modeled results, which demonstrates the utility of the assessment method for future hazard management and engineering planning. [ABSTRACT FROM AUTHOR]

Purpose: Global climate change, in particular temperature variation, is likely to alter soil microbial abundance and composition, with consequent impacts on soil biogeochemical cycling and ecosystem functioning. However, responses of belowground nitrogen transformation microorganisms to temperature changes in high-elevation terrestrial ecosystems are not well understood. Materials and methods: Here, the effects of simulated cooling and warming on the abundance and community composition of ammonia-oxidizing archaea (AOA) and bacteria (AOB), as well as the abundance of denitrifiers, were investigated using quantitative polymerase chain reaction and clone library approaches, on the basis of a 2-year reciprocal elevation translocation experiment along an elevation gradient from 3,200 to 3,800 m above sea level on the Tibetan Plateau. Results and discussion: We found that, compared with the temperature variations caused by elevation translocation, the soil origin exerted a much stronger influence on AOA abundance. There were significant effects of both soil origin and elevation translocation on AOB abundance, which was particularly decreased by elevation-enhanced (simulated cooling) and increased by elevation-decreased (simulated warming) treatments. Altered temperature affected the abundance of nirK rather than nirS and nosZ genes, and the latter two seemed to be associated tightly with the soil origin. Furthermore, the results showed that temperature changes had obvious influences on the community structure and diversity of AOB, but not AOA. More apparent response of AOB to warming than in other studies on grassland and forest ecosystems may be attributed to higher elevation and lower mean annual temperature in this study. Conclusions: Our findings thus suggest that, in comparison with AOA and denitrifying populations, AOB may respond more sensitively to natural temperature variation caused by elevation translocation in this alpine grassland ecosystem on the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

The phylogenetic relationships of European and African Barbus and their West Asian relatives in Cyprininae remain largely unresolved. Consequently, little is known about the drivers of their evolution, including the possible association of uplifting of the Qinghai-Tibetan Plateau (QTP) with the early divergence of the subfamily. We use complete sequence data of the mitochondrial DNA gene encoding the protein cytochrome b ( Cytb) to hypothesize the phylogeny of 85 species belonging to 47 genera in the Cyprininae plus 6 species from the Leuciscinae. We employ 6 other species from Cypriniformes as outgroup taxa and estimate divergence times. Our results indicate that European Barbus sensu stricto lineage including Aulopyge shares a common ancestor with specialized and highly specialized schizothoracins and the genera Cyprinion and Scaphiodonichtys. The common ancestor appears to have originated in the Qinghai-Tibetan Plateau (QTP) region about 19.4-17.8 Ma. Barbus sensu stricto lineage appears to have originated about 16.6-15.5 Ma. Small to medium sized African Barbus sensu lato appear to have had an Oriental origin about 19.1-15.3 Ma and are closely related to Asian Puntius. West Asian Carasobarbus lineage including large African Barbus sensu lato might have originated about 9.94 Ma, also in Oriental Realm and has a close relationship to Asian Neolissochilus and Tor. The large-sized Barbus sensu lato appear to have diverged from Carasobarbus about 7.7 Ma. Finally, the Cyprininae appear to have radiated rapidly into nine lineages and many sublineages from about 27.8 to 17.8 Ma, close to the time of the second-stage tectonic movements of the QTP. Our analyses provide evidence that the uplifting of the QTP drove early diversification of the Cyprininae. Our extensive sampling of species involving all of the important areas results in clear evolutionary scenario for the Cyprininae. [ABSTRACT FROM AUTHOR]

The phylogenetic relationships of European and African Barbus and their West Asian relatives in Cyprininae remain largely unresolved. Consequently, little is known about the drivers of their evolution, including the possible association of uplifting of the Qinghai-Tibetan Plateau (QTP) with the early divergence of the subfamily. We use complete sequence data of the mitochondrial DNA gene encoding the protein cytochrome b ( Cytb) to hypothesize the phylogeny of 85 species belonging to 47 genera in the Cyprininae plus 6 species from the Leuciscinae. We employ 6 other species from Cypriniformes as outgroup taxa and estimate divergence times. Our results indicate that European Barbus sensu stricto lineage including Aulopyge shares a common ancestor with specialized and highly specialized schizothoracins and the genera Cyprinion and Scaphiodonichtys. The common ancestor appears to have originated in the Qinghai-Tibetan Plateau (QTP) region about 19.4–17.8 Ma. Barbus sensu stricto lineage appears to have originated about 16.6–15.5 Ma. Small to medium sized African Barbus sensu lato appear to have had an Oriental origin about 19.1–15.3 Ma and are closely related to Asian Puntius. West Asian Carasobarbus lineage including large African Barbus sensu lato might have originated about 9.94 Ma, also in Oriental Realm and has a close relationship to Asian Neolissochilus and Tor. The large-sized Barbus sensu lato appear to have diverged from Carasobarbus about 7.7 Ma. Finally, the Cyprininae appear to have radiated rapidly into nine lineages and many sublineages from about 27.8 to 17.8 Ma, close to the time of the second-stage tectonic movements of the QTP. Our analyses provide evidence that the uplifting of the QTP drove early diversification of the Cyprininae. Our extensive sampling of species involving all of the important areas results in clear evolutionary scenario for the Cyprininae. [ABSTRACT FROM AUTHOR]

Extreme weather events have played an important role in driving the ecosystem dynamics in high altitude areas, but the underlying mechanism remains unclear. To understand if and how the soil processes of an ecosystem react to extreme drought, we manipulated a once-in-a-century meteorological extreme drought in an alpine meadow on the Tibetan Plateau, which is also known as the 'forerunner of global weather changes'. The extremity was determined by statistical extreme weather events with respect to a historical reference period from April to September during 1962-2004, where the local historical precipitation data was calculated and intensified to 100-year recurrent drought event with Gumbel I distribution. The indicators we measured included soil microbial biomass C/N/P and soil enzymatic activities of phosphatase (AP) disbounding organic phosphate, cellobiohydrolase (CBH), β-glucocidase (BG), N-releasing enzyme N-acetylglucosaminidase (NAG) as well as soil respirations, during and after the treatments. It was found that the manipulated event induced a rapid shift in microbial biomass and activities, indicating a lower resistance of the underground process. However, the microbial and biochemical parameters saw rapid recovery after the event, which meant the soil processes enjoyed high resilience. The high responsiveness and lag-time effects of the soil indicators rendered new horizons for us to evaluate the interaction between the extremes and the ecosystem stability. Our study indicated that the once-in-a-century extreme drought induced very short term response in the soil biotic process, and the soil processes worked to buffer against such events under the observation period. [ABSTRACT FROM AUTHOR]

In this article the author reflects upon a paper by researcher G. F. Kang and colleagues related to the characteristics of regional tectonics and crustal magnetic anomaly in the Qinghai-Tibet Plateau area. The author discusses the limitations in Kang and colleagues' usage of the U.S. National Geophysical Data Center's (NGDC) lithospheric magnetic field model number 720 and highlights difference in various aeromagnetic anomalies for different blocks in the plateau.

Background and aims: Few studies have investigated the effect of nitrogen (N) fertilizer on ecosystem respiration (Re) under mixed legume and grass pastures sown at different seeding ratios,and data are almost entirely lacking for alpine meadow of the Tibetan Plateau. Our aim was to test the hypothesis that although a combination of legumes with grass and N fertilizer increases Re the combination decreases Re intensity (i.e. Re per unit of aboveground biomass) due to greater increases in aboveground biomass compared to increases in Re. Methods: This hypothesis was tested using different seeding ratios of common vetch ( Vicia sativa L.) and oat ( Avena sativa L.) with and without N fertilizer on the Tibetan plateau in 2009 and 2010. Re was measured using a static closed opaque chamber. Re intensity was estimated as the ratio of seasonal average Re during the growing season to aboveground biomass. Results: Compared with common vetch monoculture pasture, mixed legume-grass pastures only significantly decreased Re intensity (with a decrease of about 75 %-87 %) in the drought year 2009 due to greater increases in aboveground biomass compared to increases in Re. There were no significant differences in Re and Re intensity among different seeding ratios of oat and common vetch in either year. N fertilizer significantly decreased Re intensity for common vetch monoculture pasture by 24.5 % in 2009 and 69.5 % in 2010 although it did not significantly affect plant production and Re. Conclusions: From the perspective of forage yield and Re, planting mixed legume-grass pastures without N fertilizer is a preferable way to balance the twin objectives of forage production and mitigation of atmospheric greenhouse gas emissions in alpine regions. [ABSTRACT FROM AUTHOR]

Knowledge about methanotrophs and their activities is important to understand the microbial mediation of the greenhouse gas CH under climate change and human activities in terrestrial ecosystems. The effects of simulated warming and sheep grazing on methanotrophic abundance, community composition, and activity were studied in an alpine meadow soil on the Tibetan Plateau. There was high abundance of methanotrophs (1.2-3.4 × 10 pmoA gene copies per gram of dry weight soil) assessed by real-time PCR, and warming significantly increased the abundance regardless of grazing. A total of 64 methanotrophic operational taxonomic units (OTUs) were obtained from 1,439 clone sequences, of these OTUs; 63 OTUs (98.4%) belonged to type I methanotrophs, and only one OTU was Methylocystis of type II methanotrophs. The methanotroph community composition and diversity were not apparently affected by the treatments. Warming and grazing significantly enhanced the potential CH oxidation activity. There were significantly negative correlations between methanotrophic abundance and soil moisture and between methanotrophic abundance and NH-N content. The study suggests that type I methanotrophs, as the dominance, may play a key role in CH oxidation, and the alpine meadow has great potential to consume more CH under future warmer and grazing conditions on the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Purpose: Small but highly bioactive labile carbon (C) and nitrogen (N) pools are of great importance in controlling terrestrial C and N fluxes, whilst long-term C and N storage is determined by less labile but relatively large sizes of C and N pools. Little information is available about the effects of global warming and grazing on different forms of C and N pools in the Qinghai-Tibet Plateau of China. The aim of this study was to investigate the effects of warming and grazing on the sizes of different soil labile C and N pools and N transformation in this region. Materials and methods: A free-air temperature enhancement system in a controlled warming-grazing experiment had been implemented since May 2006. Infrared heaters were used to manipulate temperature, and a moderate grazing intensity was simulated by Tibetan sheep. After 3 years' warming, soil samples were taken from the four treatment plots: no warming with no grazing; no warming with grazing; warming with no grazing; and warming with grazing. Concentrations of inorganic N in the 40-cm soil profiles were measured by a flow injection analyser. Microbial biomass C (MBC) and microbial biomass N (MBN) were measured by the fumigation-extraction method, and soluble organic C (SOC) and soluble organic N (SON) were determined by high-temperature catalytic oxidation. Total N (TN), C isotope composition (δC) and N isotope composition (δN) were determined using an isotope ratio mass spectrometer. Net N transformation under low temperature was studied in a laboratory incubation experiment. Results and discussion: Warming and grazing treatments affected soil C and N pools differently, and these effects varied with soil depth. Warming significantly increased TN, MBC, MBN, and SON and decreased δC at the 10-20 and 20-30 cm soil depths, whilst grazing generally decreased SON at the 10-20 and 20-30 cm, and MBC at 20-30 cm. At the 0-10 cm depth, neither warming nor grazing alone affects these soil parameters significantly, indicating that there could be considerable perturbation on the soil surface. However, grazing alone increased NO-N, total inorganic N, SOC and δN at the 0-10 cm depth. Incubated at 4°C, warming (particularly with grazing) led to net immobilization of N, but no-warming treatments led to net N mineralization, whilst nitrification was strong across all these treatments. Correlations between MBC and SOC, and TN and MBN or SON were positive. However, SON was less well correlated with TN and MBN compared with the highly positive correlations between SOC and MBC. Conclusions: It is clearly demonstrated that warming and grazing affected labile C and N pools significantly, but differently after 3 years' treatments: Warming tended to enlarge labile C and N pools through increased litter inputs, whilst grazing tended to increase inorganic N pools, decrease SON and accelerate N cycling. Grazing might modify the mode that warming affected soil C and N pools through its strong impacts on microbial processes and N cycling. These results suggested that interactive effects of warming and grazing on C and N pools might have significant implications for the long-term C and N storage and productivity of alpine meadow ecosystem in the Qinghai-Tibet Plateau of China. [ABSTRACT FROM AUTHOR]

This paper reports a study on reconstructing temperature series for ten regions of China over the last 1000 years with a time resolution of 10 a. The regions concerned are: Northeast, North, East, South China, Taiwan, Central, Southwest, Northwest China, Xinjiang and Qinghai-Tibet Plateau. A variety of proxy data, such as ice core, tree-rings, stalagmites, peat, lake sediments, pollen and historical records, were validated with instrumental observations made in the last 120 years, and applied in the reconstruction of the temperature series. A temperature series for whole China is then established by aver- aging the ten regional series with a weighting proportional to the area of each region. Finally, temperature variations for the last 1000 years are examined, with special focus placed on the characteristics of the Medieval Warm Period (MWP), the Little Ice Age (LIA), and Modern Warming (MW). [ABSTRACT FROM AUTHOR]

This paper presents a large data set on carbon isotope composition (δ13C) of modern soils which were collected under the main vegetation communities along an altitude of 1250–5500 m above sea level in the Qinghai-Tibetan Plateau. The δ13C values of 198 samples range from -28.6 to -15.1‰ versus PDB and exhibit a clean relation to different vegetation communities from forest (-25.9 ± 1.2‰) to shrub (-24.7 ± 1.4‰), steppe (-23.1 ± 1.3‰), alpine meadow (-23.6 ± 0.7‰), alpine desert steppe (-21.3 ± 1.6‰), and alpine desert (-18.9 ± 2.5‰). We attributed the observed variability in δ13C values to that the mean annual precipitation (MAP) and the mean annual temperature (MAT) are the main factors controlling the distribution of vegetation types in the Tibetan Plateau, which causes the change in carbon isotope composition of modern soils at any given altitude. The result of both linear and nonlinear regression analyses also confirms that MAP and MAT are the major factors affecting the δ13C values of surface soils. In the absence of favorable moisture and temperature conditions, low pCO2 alone is not sufficient to cause the distinct changes in carbon isotope composition of modern soils in the Tibetan Plateau. This study provides some fundamental information on the carbon isotope composition of terrestrial carbon pools and bears some practical significance for the use of carbon isotope data to document vegetation changes and environmental conditions of the high plateau in the past. [ABSTRACT FROM AUTHOR]

Plant specimens are collected from the areas between latitude 27°42'N and 40°57'N, and longitude 88°93'E and 103°24'E, with an altitudinal range from 2210 to 5050 m above the sea level in Qinghai-Tibetan Plateau. The stable carbon isotope analysis indicates that two of Chenopodiaceae and six of Poaceae in the samples are C4 plants. Four of the C4 plants are found in 11 spots with altitudes above 3800 m, and Pennisetum centrasiaticuin, Arundinella yunnanensis and Orinus thoroldii are present in six spots above 4000 m, even up to 4520 m. At low CO2 partial pressure, that sufficient energy of high light improving C4 plant's tolerance of low temperature and precipitations concentrating in growing season probably are favorable for C4 plants growing at high altitude in Qinghai-Tibetan Plateau. [ABSTRACT FROM AUTHOR]

It is still debatable whether temperature or precipitation mainly triggers spring vegetation green-up (SVG) in alpine dry ecosystems on the Tibetan Plateau. As phenological sensitivity to the arrival of monsoon-season rainfall would allow plants to simultaneously avoid drought and frost damages in the early growing season, we hypothesize that rainy season onset (RSO) rather than temperature mainly drives the spatiotemporal variability of SVG across alpine dry ecosystems over the Tibetan Plateau. Dates of RSO and SVG across 67 target areas nearby 67 weather stations over the Tibetan Plateau were calculated from time-series data of daily mean temperature and precipitation (1974–2013) and of the Normalized Difference Vegetation Index from the Moderate Resolution Imaging Spectroradiometer (2001–2013), respectively. Satellite-derived SVG was validated by 7-year observations (2007–2013) for leaf emergence of dominant species in alpine meadows along elevations (4400–5200 m) in Damxung of Tibet. We found that SVG generally synchronized with or was somewhat later than RSO although seasonal air temperatures were already continuously above 0 °C in 1 month before SVG dates. In pooled data across sites and years, the analysis of linear mixed model indicated that RSO (F = 42.109) and its interactions with pre-SVG precipitation (F = 6.767) and temperature (F = 4.449) mainly explained the spatio-temporal variability of SVG, while pre-SVG temperature and its interaction with precipitation did not have significant effects on SVG. Our data supported the hypothesis, suggesting that synchronization of SVG and RSO is a general spring phenological strategy across alpine dry ecosystems under influence of monsoon climate. [ABSTRACT FROM AUTHOR]

We conducted a comparative phylogeographic analysis of three rodent species ( Meriones meridianus , Dipus sagitta , and Allactaga sibirica ) on the northeast margin of the Qinghai-Tibetan Plateau, Qaidam Basin, the Hexi Corridor and Tengger-Badain Jaran Desert based on sequences of the mitochondrial cytochrome b gene of 264 individuals from 22 sampling sites. Our analyses indicated that the intraspecific genetic structures of the three rodents did not arise through the same historical events and that they did not show parallel geological and climatic histories. M. meridianus and D. sagitta , which showed low-altitude distributions, experienced less isolation because they stayed in stable favorable habitats. On the other hand, A. sibirica was strongly isolated due to fragmented habitats caused by the complex topography of the high-altitude regions in the Qaidam Basin. The two desert-dwelling rodent species, M. meridianus (0.023–0.014 Mya) and D. sagitta (0.013–0.009 Mya), showed sudden demographic expansion during the Last Glacial Maximum, with the disappearance of the ancient lakes and the maximum extent of desert expansion. A. sibirica is mostly distributed in the grassland mountain regions. Thus, steppe expansion and a sharp decrease in the ancient lake size significantly affected the species’ distribution during the Middle Pleistocene (0.525 Mya). No clear signal of population expansion was observed for this species, which might be attributable to successive phases of population bottlenecks obscuring the indicators of expansion. Our data reflect the continual interaction of extrinsic and intrinsic factors in generating intraspecific phylogeographic patterns and faunal diversity. [ABSTRACT FROM AUTHOR]