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To study the viscosity coefficient and thickness of the viscous layer on the Tibetan Plateau, the relationship between the change in viscosity coefficient and thickness of a lower crustal flow and the change in elevation has been investigated based on the principle of a pipeline flow with different viscosity and thickness of terrain elevation. The viscosity and thickness of the lower crustal flow in different directions were determined based on the changes in the terrain along different directions on the Tibetan Plateau. The following results were obtained: (1) The greater the viscosity and the smaller the thickness of the lower crustal conduit flow, the steeper the ground elevation change formed; (2) The maximum viscosity coefficient in the region from India to the Kunlun Mountains in the southern Tibetan Plateau through the Himalayan boundary is approximately 1020Pas, and the thickness of the conduit flow is approximately 25 km. (3) The maximum value of the viscosity coefficient of the lower crustal flow in the region ranging from the Tibetan Plateau to the Qinghai- Gansu section is attained when the flow thickness in this region approaches 40 km (4) The maximum value of the viscosity coefficient of the lower crustal flow in the region ranging from the Tibetan Plateau to the Qinghai- Gansu section is attained when the flow thickness in this region approaches 40 km., which does not substantially differ from that of the region ranging from the Tibetan Plateau to the Qinghai-Gansu area. (5) The maximum viscosity coefficient of the lower crustal flow from the southeast of the Tibetan Plateau to Yunnan is approximately 1018Pas, and the thickness is approximately 32 km, which differs from the flow thickness in the Sichuan Basin and Qinghai-Gansu regions. The results show variations in the viscosity of the flow along different directions on the Tibetan Plateau, in addition to considerable variation in the thickness of the lower crustal channel flow from region to region, with the overall characteristics of thinness in the west and thickness in the east. The results of the four profiles reveal that the channel flow thickness is the steepest at the southwest border of the Tibetan Plateau with India. This paper presents a reasonable interpretation of the geomorphology of the Tibetan Plateau using different thickness and viscosity coefficients of the lower crustal channel flow model. In this paper, a possible mechanism for the formation of the Tibetan Plateau topography is explained using a horizontal pipe flow for four profiles of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Tibetan Plateau Vortices (TPVs) are important synoptic systems that affect precipitation over the Tibetan Plateau (TP) and downstream weather. By using daily reanalysis data provided by ECMWF and the objective identification methods, the study identified the basic spatiotemporal changes of TPVs, clustered the TPVs by different dynamic circulation types and explored the dynamic circulation background of the classified TPVs in the midwestern TP and their relationship with thermal factors, such as sensible heat and soil moisture. The results show that TPVs in the midwestern TP exhibited an increasing trend from May to August, resulting from the coupling of dynamics with thermal forcing. The related synoptic circulations were divided into four types according to the dynamic circulations: the shortwave trough, the longwave trough, the shear line and the plateau anticyclone type. Among the TPVs, the percentage of TPVs in the shortwave and longwave trough type was relatively large, accounting for 48.7% and 31.5%, respectively, both of which were dominated by the coupling of increased sensible heat and decreased soil moisture. The shear line type was less affected by thermal factors, and mainly driven by dynamic factors, whereas the soil moisture gradient was responsible for the plateau anticyclone type. The simulation experiment also proved this conclusion. [ABSTRACT FROM AUTHOR]

A non-motile, Gram-staining-negative, orange-pigmented bacterium called herbae pc1-10T was discovered in Tibet in the soil around Pyrola calliantha H. Andres' roots. The isolate thrived in the temperature range of 10–30 °C (optimal, 25 °C), pH range of 5.0–9.0 (optimum, pH = 6.0), and the NaCl concentration range of 0–1.8% (optimal, 0%). The DNA G+C content of the novel strain was 37.94 mol%. It showed the function of dissolving organophosphorus, acquiring iron from the environment by siderophore and producing indole acetic acid. Moreover, the genome of strain herbae pc1-10T harbors two antibiotic resistance genes (IND-4 and AdeF) encoding a β-lactamase, and the membrane fusion protein of the multidrug efflux complex AdeFGH; antibiotic-resistance-related proteins were detected using the Shotgun proteomics technology. The OrthoANIu values between strains Chryseobacterium herbae pc1-10T; Chryseobacterium oleae CT348T; Chryseobacterium kwangjuense KJ1R5T; and Chryseobacterium vrystaatense R-23566T were 90.94%, 82.96%, and 85.19%, respectively. The in silico DDH values between strains herbae pc1-10T; C. oleae CT348T; C. kwangjuense KJ1R5T; and C. vrystaatense R-23566T were 41.7%, 26.6%, and 29.7%, respectively. Chryseobacterium oleae, Chryseobacterium vrystaatense, and Chryseobacterium kwangjuense, which had 16S rRNA gene sequence similarity scores of 97.80%, 97.52%, and 96.75%, respectively, were its closest phylogenetic relatives. Chryseobacterium herbae sp. nov. is proposed as the designation for the strain herbae pc1-10T (=GDMCC 1.3255 = JCM 35711), which represented a type species based on genotypic and morphological characteristics. This study provides deep knowledge of a Chryseobacterium herbae characteristic description and urges the need for further genomic studies on microorganisms living in alpine ecosystems, especially around medicinal plants. [ABSTRACT FROM AUTHOR]

Since the continental collision between the Indian and Eurasian plates began about 50 Ma ago, southeastern Tibet (SET) has undergone complex tectonic deformation. In this study, we investigate fine scale structural features of the crustal and upper mantle depths (<250 km) beneath SET, which hold important clues to understanding the dynamic processes related to this collision. A 3D shear velocity model is constructed through jointly inverting Rayleigh wave phase velocity and teleseismic body wave data from more than 650 stations. Our 3D model identifies three independent low‐velocity zones (LVZs) in the mid‐lower crust with unprecedented details. More specifically, we observe a prominent LVZ beneath the North Chuan‐Dian Block, which is well separated from another LVZ beneath the Tengchong volcano in the south. This LVZ beneath the volcano represents a focused magma reservoir in the crust whose origin is potentially linked to the mantle upwelling associated with the eastward subduction of the Indian plate. The third LVZ, observed around the Xiaojiang Fault, likely represents a separated and mechanically weak layer in the mid‐lower crust due to the combined effects of regional crustal thickening under the southeastward plateau expansion, mantle upwelling, and shear heating of strike‐slip faults. In the upper mantle, we observe strong velocity reductions both in localized areas beneath the Tibetan Plateau and the broad region south of 26°N. These low velocity anomalies are sitting above high velocity anomalies at deeper depths, suggesting their association with lithospheric thickening and delamination processes. Plain Language Summary: Southeastern Tibet (SET) has undergone complex geological evolution due to the plate collision. To better understand the related dynamic processes, we present a high‐resolution 3D S‐wave velocity model from the earth surface to the depth of 250 km by using surface wave and body wave data. Our model shows three independent crustal low‐velocity zones (LVZs). Especially, the one beneath the Tibetan Plateau is seen to be well separated from the one beneath the Tengchong volcano which represents the hot magma upwelling related to the eastward subduction of the Indian plate. In addition, another LVZ around the Xiaojiang Fault probably represents a separated and mechanically weak layer that is attributed to the regional crustal thickening under the southeastward plateau expansion, mantle upwelling, and shear heating of strike‐slip faults. In the upper mantle, we observe strong velocity reductions both in localized areas beneath the Tibetan Plateau and the broad region south of 26°N. Many of these low velocity anomalies are sitting above high velocity anomalies at deeper depths, suggesting their origin of lithospheric thickening and delamination processes. Key Points: A 3D velocity model of SE Tibet is obtained via a joint inversion of surface wave phase velocity and teleseismic body wave dataOur model reveals spatial distributions of three isolated mid‐lower crustal low‐velocity zones with unprecedent detailsBroad low velocities in the upper mantle imply mantle upwelling related to the lithospheric delamination and slab subduction [ABSTRACT FROM AUTHOR]

Continued climate warming and precipitation fluctuations are expected to further affect aboveground net primary productivity (ANPP) across alpine grasslands, with associated implications for ecosystem functions. The spatial and temporal variability of ANPP in Tibetan Plateau (TP) grasslands and its response to temperature and precipitation were investigated in this study, based on the ANPP estimated by means of ensemble analysis of multiple machine learning models. First, the response of the spatial distribution of ANPP to variations in the precipitation gradient was nonlinear and showed an S-shaped growth pattern, which could be divided into four stages (stationary, rapid growth, slower growth, and saturation) corresponding to arid (mean annual precipitation (MAP) < 250 mm), semiarid (250 mm < MAP < 450 mm), semihumid (450 mm < MAP < 650 mm) and humid (MAP > 650 mm) precipitation regimes, respectively. Second, regional precipitation regimes affected the sensitivity of ANPP's interannual variability to temperature and precipitation; ANPP is more sensitive to temperature in wetter areas than in dryer areas of the TP region. The results of our study suggest that in the region of Tibetan Plateau, the response of grassland ANPP variation to climate was constrained by the background precipitation regimes. [ABSTRACT FROM AUTHOR]

Palaeoflood records have provided the extended perspective required to understand linkages between extreme floods and climate variability. During our palaeo‐hydrological investigations, two units of palaeoflood slackwater deposits (SWD) were found on the river banks in the Maqu‐Oula reach along the mainstream of the Yellow River on the northeast (NE) Tibetan Plateau. A series of samples were taken from the sediment profiles at Taiwuruo (TWR) and Daerqiong (DEQ) sites for laboratory analysis. Grain‐size distribution and micro‐morphological characteristics of quartz grains indicate that these well‐sorted SWD units were derived from the suspended sediment load in floodwater. They have recorded two episodes of overbank flooding in the Yellow River source area. Using the optically stimulated luminescence (OSL) dating technique, the first episode of overbank flooding was dated to 13.6–13.0 ka and correlated with the Bølling–Allerød warm interval of the last deglaciation. The second episode occurred at 11.0–10.0 ka, that is, the early Holocene. In a warm‐humid climate, these overbank flooding episodes may have resulted from the accelerated melting of mountain glaciers and snow over the headwaters of the alpine and subalpine regions on the NE Tibetan Plateau. These results are important in facilitating an in‐depth understanding of the hydro‐climatic response of the Tibetan Plateau to global climate warming occurring presently. [ABSTRACT FROM AUTHOR]

Assessment of soil organic carbon (SOC) concentration in high‐altitude shrublands is essential for understanding C dynamics in terrestrial ecosystems. Hence, we investigated the SOC concentration and its influencing factors using 198 soil profiles (0–100 cm) from 66 sites between 2011 and 2013 in the north‐eastern Tibetan Plateau shrublands. SOC concentration was different under different shrubland types, with SOC concentration significantly greater in the alpine shrublands relative to the desert shrublands, whereas SOC concentration showed limited increases with altitude. Both mean annual temperature (MAT) and mean annual precipitation (MAP) have positive relationships with SOC concentration, and their relationships are moderate. Compared with MAT, a correlation between MAP and variation in SOC concentration was larger. Meanwhile, with increasing soil depth, a correlation between variation in SOC concentration and climatic factors was smaller. Soil pH seems to be a robust factor that not only had a significant negative correlation with SOC, but also played an important role in regulating a correlation between climatic condition and variation in SOC concentration. Controls on variation of SOC concentration on the Tibetan Plateau help to understand soil C dynamics in terrestrial ecosystems. Highlights: SOC concentration was different under different shrubland types, whereas SOC concentration showed limited increases with altitude.Compared with MAT, a correlation between MAP and variation in SOC concentration was larger.Soil pH seems to be a robust factor that had a significant negative correlation with SOC concentrationSoil pH was also important for regulating a correlation between climatic condition and variation in SOC concentration. [ABSTRACT FROM AUTHOR]

The Mesozoic–Cenozoic Zheduo–Gongga Massif, eastern Songpan–Ganze Terrane, can provide important clues for the crustal evolution in response to syn‐ and post‐orogeny. Here, we document petrological and geochemical characteristics of Early Jurassic granites (181.0 ± 2.2 Ma) within the massif along the Xianshuihe Fault in the eastern Tibetan Plateau. The granites have high contents of SiO2, Na2O + K2O, FeOT/MgO, 10,000 × Ga/Al, REE (except Eu) and HFSE (e.g., Nb, Ta, Zr, Hf), low CaO, TiO2, P2O5 and negative Eu, Sr, and Ba anomalies. Zircon REE shows a similar pattern with the whole‐rock REE. Our new data demonstrate weakly peraluminous A‐type affinity with A/CNK >1.0 and alkali‐calcic, ferroan features. Zircon saturation temperatures and geochemical features (e.g., high SiO2 and low MgO contents, high Rb/Ba and Rb/Sr ratios) indicate that the granites resulted from high‐temperature (>800°C) partial melting of Triassic flysch rocks in relatively shallow crust (<500 MPa or <20 km). Zircon εHf(t) values range from 0.55 to 2.91 and the corresponding two‐stage TDMC are older than the neighbouring Kangding complex and Yangtze margin, implying possible contribution of mantle materials to the parent magma. Considering the tectonic events and the regional geology, the magma was generated in a post‐collisional setting, which was possibly driven by the upwelling of hot mid–lower crustal materials due to the break‐off of subducted Palaeo‐Tethys Ocean slab. Under this situation, the magma may move upwardly into the pre‐existing Xianshuihe Fault during the post‐collisional extension of the thickened crust. Thus, slab break‐off played a key role in the genesis of the Zheduo–Gongga Massif studied herein. [ABSTRACT FROM AUTHOR]

In this study, we analyze the relationships between summer afternoon low cloud cover and environmental conditions over the Tibetan Plateau (TP). Using in situ measurements, satellite data, and reanalysis, and based on theoretical analysis, we find that there is stronger thermal turbulence, lower temperature, and higher frequency of low cloud formation for the same surface relative humidity over the eastern and central TP compared with eastern China. With the same sensible heat flux, decreased air density enhances buoyancy flux, which increases the planetary boundary layer height and moisture vertical transport. At the same time, with the same near‐surface relative humidity, lower temperature over the TP decreases the lifting condensation level, which increases the probability of the air parcel reaching this level. Compared to the low‐elevation region in eastern China, these two mechanisms enhance low cloud occurrence in the afternoon over the TP. Plain Language Summary: Previous studies suggested that planetary boundary layer processes play an important role in the formation of more low clouds in the afternoon over the Tibetan Plateau (TP). However, detailed mechanisms for the differences in low cloud occurrence in the afternoon over the TP versus eastern China (low‐elevation region) remain unclear. Using in situ measurements, satellite data, and reanalysis, and based on theoretical analysis, we first quantify the more frequent low cloud occurrence over the TP, and then propose two mechanisms: (i) compared to eastern China, in the afternoon over the TP, the lower near‐surface temperature results in a lower height where condensation occurs (given the same relative humidity), and (ii) the lower air density (given the same surface sensible heat flux) results in a larger buoyancy flux, leading to a deeper boundary layer. These two mechanisms work together to increase cloud formation in the afternoon over the TP. Key Points: There are more summer afternoon low clouds over the Tibetan Plateau (TP) than over eastern China as a result of two mechanismsCompared to eastern China, with the same relative humidity, lower temperature over the TP results in a lower lifting condensation levelWith the same surface sensible heat flux, lower air density over the TP results in a larger buoyancy flux and a deeper boundary layer [ABSTRACT FROM AUTHOR]

Understanding how biotic and abiotic filters drive plant distributions is critical for informing restoration efforts of degraded lands. However, it remains unclear whether or not it is possible to develop efficient restoration strategies that are based on field investigations? Here, we conducted a field‐based investigation along a land degradation gradient on the Tibetan Plateau. Along this gradient, we compared species composition, Pianka's niche overlap, and total aboveground biomass among grasses, sedges, legumes, and forbs. We also used Faith's (1992) phylogenetic diversity index (PD) and the net relatedness index (NRI) to measure community phylogenetic patterns. To understand the effects of abiotic filtering, we measured soil pH, moisture, electrical conductivity, total soil organic carbon, microbial biomass carbon, and microbial biomass nitrogen. Our results show that grasses replaced sedges and mesoxerophytes replaced mesohydrophytes with increasing land degradation. We also found that niche overlap declined with increasing degradation intensity. Furthermore, grass biomass increased, while sedges and legumes decreased, and forb biomass showed a hump‐shaped relationship with degradation intensity. In addition, the communities transitioned from a clustered to a more random phylogenetic pattern. Soil conditions changed from acidic to alkaline and from fertile to harsh (p <.05). High niche overlap indicates a high biotic filtering at lightly degraded land where abiotic filtering is less stressful. However, when degradation is intense, abiotic filtering is apparent, as indicated by low levels of niche overlap. Overall, we suggest that distantly related, arid tolerant and hardy plants, and soil reclamation should be considered in degraded alpine lands restoration. [ABSTRACT FROM AUTHOR]

The Xianshuihe Fault Belt (XSF), along which the syntectonic Zheduoshan batholith was emplaced, has great significance for the reconstruction of the tectonic framework in the eastern margin of the Tibetan Plateau. In this contribution, formation process and evolution of the XSF are discussed based on the structural deformation in the field and the geochronology of Zheduoshan batholith. The results show that the XSF current arc‐shaped protrusion to the north‐east probably was formed by a fracture of the clockwise rotation compression that extended northward to the periphery with the eastern Himalayan tectonic syntaxis as the centre. It is a complex fault belt formed by the superposition of multi‐stage structures. In the early‐stage formation and evolution of the XSF, the Oligocene‐Miocene migmatite zone and Miocene granites of the Zheduoshan batholith were emplaced. Among them, the lower limit of the XSF's initial activity time was not less than 47 Ma that was limited by the Zircon U–Pb geochronology of migmatite zone formed under the compression system. During the emplacement of Miocene granites, the XSF underwent a process from compression to sinistral strike‐slip, and the geochronology indicates that the onset of the XSF sinistral strike slip should not be less than 14 Ma. After syntectic magmatism, the XSF also experienced the shear deformation (from ductile to brittle) with sinistral kinematics. 40Ar‐39Argeochronology results show that the ductile shear deformation mainly occurred around 5.5–3.2 Ma and accompanied a staged and differential uplift from north to south. It extended to the south along the weak crustal zone of Anninghe, Daliangshan, Xiaojiang, and other faults, forming the Xianshuihe–Anninghe–Xiaojiang sinistral strike‐slip fault system on the eastern margin of the Tibetan Plateau, and large‐scale sinistral strike slip began around 5 Ma. Our new insights lay a foundation for understanding and dissecting the formation and evolution of the Tibetan Plateau eastern margin. [ABSTRACT FROM AUTHOR]

The Dadu River in the eastern Tibetan Plateau has the potential to record transient variations of tectonic uplift since the Late Cenozoic. In this study, we extracted bedrock channels of the Dadu River drainage basin from the 30 m ASTER digital elevation model. The longitudinal river profiles were then analyzed, and three generations of knickpoints were recognized via the slope area method. By solving the analytical solution of the linear transient stream power incision model, we determined a Late Cenozoic history of regional tectonic uplift. The results reveal slow pre–middle Miocene uplift rates (<0.1 mm/a) and then increased gradually to 0.33 ± 0.03 mm/a since 12–15 Ma until present. This increase of uplift rate from bedrock channel inversion is consistent with the regional findings of low‐temperature themochronology, emphasizing the potential and significance to utilize channel profiles to infer the tectonic uplift history. Plain Language Summary: Recently, numerous thermochronology studies have provided constraints on the timing of rapid denudation along the eastern Tibetan Plateau. However, the rates of denudation/uplift determined by thermochronological profiles are often given as an average since a certain time duration. Thus, it is difficult to quantify the history of the tectonic uplift and whether uplift has been uniform or varied through time. We used the linear simulation method and inverted the longitudinal river profiles to decipher the Late Cenozoic uplift history of the eastern Tibetan Plateau. The results reveal that before the middle Miocene, the uplift rate was slow (<0.1 mm/a), and it increased gradually to 0.33 ± 0.03 mm/a since 12–15 Ma until present. Key Points: Linear inversion of the longitudinal river profiles for Tibetan Plateau uplift historyIncrease of the uplift rate since 12-15 Ma, consistent with regional resultsNew evidence of the late Miocene tectonic uplift in eastern Tibet [ABSTRACT FROM AUTHOR]