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Anthropogenic activity is an important driver of changes in the chemistry of nutrients (N, P, and Si) over watersheds at the sub-continental scale (e.g., 106 km2) and can markedly modify their seaward fluxes to the global ocean. In the present study, we reviewed the current status of nutrient chemistry in Changjiang (Yangtze River) based on data collected through 11 expeditions along a river course spanning 4,500 km and 15–20 major tributaries during 1997–2016 as well as monthly monitoring at the river mouth since 1980. The data were analyzed together with published results in the literature to synthesize the recent developments and current state of nutrients in the Changjiang. Previously published results from the Qinghai-Tibetan Plateau head waters were included to realize the systematics of nutrients for the whole drainage basin. Here, we showed that tributaries of the upper reaches of watersheds collectively determine the regime with high concentration and skewed species ratio of nutrients in the Changjiang mainstream, producing profound effects over a water course of 2,000–2,500 km further downstream and until the river mouth. Moreover, using data across the Three Gorges Reservoir (TGR) during 2003–2016, we evaluated the trapping and/or amplifying effects of the Three Gorges Dam (TGD) on nutrient chemistry. Tide-influenced river delta contributed an additional 20% dissolved inorganic phosphorus and 5–10% dissolved inorganic nitrogen and dissolved silicates to the seaward flux, dramatically affecting the stoichiometry of nutrients at the river mouth. Next, based on compiled data on supply and export, legacy nutrients were evaluated. Both nitrogen and phosphorus are in the accumulation phase over the watersheds, and the legacy nutrient fluxes are much higher than the annual riverine seaward fluxes. Finally, we demonstrated that the seaward fluxes of anthropogenic nutrients from the Changjiang exceed those from other top 10 largest rivers on this planet, which can be attributed to land use changes in the China over the last three to four decades. [ABSTRACT FROM AUTHOR]

More than 185 hot springs have been recently discovered in the eastern Tibetan Plateau geothermal belt (also called the Kangding-Litang-Batang geothermal belt) (98-102°E, 28-32°N). Among them, more than 60% of springs have temperatures of >40 °C, and 11 springs have temperature higher than the local water boiling point. These hot springs are mostly exposed near the fault or valley areas, as bandings in reservoirs of Triassic carbonate rocks and clastic quartz sandstone or in fractured granite and intrusive rocks. The geothermal belt can be subdivided into the Batang-Xiangcheng geothermal field, the Ganzi-Litang geothermal field, and the Luhuo-Kangding geothermal field, which are controlled by the Jinsa fault, Xiangcheng fault, Litang fault, and Xianshuihe fault, respectively. Radiogenic heat from the Mesozoic and Cenozoic granites, possible ductile crustal flow beneath the lower crust, and frictional heat generated by active strike-slipping along faults are the significant heat resources for the geothermal genesis. Frictional heat caused by the slipping along the Xianshuihe fault is the main thermal source for the Luhuo-Kangding geothermal field, whereas magma melting heat is the main source for the Batang-Xiangcheng geothermal field. Glacier water and river water are the main water supply sources, and the fracture serves as the main channel for runoff and hot water flow. The activity intensity and magnitude of the Kangding-Litang-Batang geothermal anomaly were lower than those of the geothermal fields of Yangbajing and Tengchong in the central and southern Tibetan Plateau, respectively, which indicates that the eastern Tibetan Plateau has a strong heat flow background. [ABSTRACT FROM AUTHOR]

Erosion at the Earth's surface is a major factor controlling the landscape evolution. Cosmogenic nuclides provide a valuable tool for the quantitative study of surface erosion. We employ cosmogenic nuclide 21 Ne analysis to quantify the average erosion rate in the Shapotou area, at the northeastern margin of the Tibetan Plateau, based on the steady-state erosion model. A series of erosional surfaces on the river terraces generated by the Yellow River incision offer us a new approach to determine whether the cosmogenic 21 Ne nuclide inventory has reached equilibrium between nuclide production and loss by surface erosion. Using the steady-state 21 Ne concentration, the average erosion rate in this area is determined to lie between 0.54 ± 0.11 cm ka −1 and 0.72 ± 0.21 cm ka −1 . A depth profile of the subsurface cosmogenic 21 Ne concentrations provides additional evidence for the validity of our steady-state erosion model. Our results reveal that the erosion rate in this area lags significantly behind the incision rate of the Yellow River, which increased the local relief in the Shapotou area. [ABSTRACT FROM AUTHOR]

The implementation of pasture contracting policies in the Tibetan Plateau has been of widespread concern in the scientific community and related government departments. Studying the effects of the implementation of pasture contracting policies will help us understand herders’ attitudes toward those policies and to amend existing policies effectively. This paper analyzes 135 herder families’ grazing management behavior using participatory rural appraisal (PRA), quantitative analysis and a Logistic regression model in three townships of Nagqu County in remote areas of the Tibetan Plateau, China. The results show that the herders have become settled and are no longer nomadic, so the settlement project has basically been completed and the policy of contracting for grazing rights is being gradually implemented in Nagqu County. Since the grazing rights and pastures were under contract, group-based management has been widely accepted in this area, which helps the herders deal with constraints, such as limited pasture area, a small grazing radius, controlled family animal husbandry and an uneven distribution of water. The herders that have more family members available for labor, higher proportion of family members with good health, and higher income from animal husbandry tend to choose household-based management. Herders tend to choose group-based management when higher quality winter pastures are available. [ABSTRACT FROM AUTHOR]

Vertical–axis rotations recorded by paleomagnetic results from the northeastern Tibetan Plateau afford new insights into the tectonic processes related to the growth of the Tibetan Plateau. Here, geochronological and paleomagnetic investigations on the Cretaceous–Tertiary basalt sequences within the West Qinling Mountain were conducted to decipher the vertical–axis rotations of the northeastern Tibetan Plateau. Potassium–argon (K Ar) results from the basaltic rocks reveal two time episodes of extrusive volcanism, 123–90 Ma and 21–15 Ma. Comparisons between the obtained paleomagnetic data and the equivalent age–expected directions of the Eurasia and the North China block respectively, indicate that 10–20° clockwise rotation occurred in the West Qinling Mountain only after ∼15 Ma. Combined with the previous estimation of Eocene clockwise rotation in the Xining–Lanzhou region north of the West Qinling Mountain, we conclude that two–stage clockwise tectonic rotation occurred in different parts of the northeastern Tibetan Plateau, related to different deformational kinematics. The Eocene–clockwise rotation was likely in response to N S trending normal faulting, suggesting that inboard extension in East Asia drove the rotation within the outmost region of the Tibetan Plateau. In contrast, the mid–Miocene clockwise rotation was linked to crustal right lateral shear in the northeastern corner of the Tibetan Plateau when the plateau grew to its northern margins. • Potassium‑argon dates two episodes of extrusive volcanism at 123–90 and 21–15 Ma in the West Qinling Mountain. • Both stages of basalt flows recorded 10–20°of clockwise rotation within the West Qinling Mountain. • The Miocene clockwise rotation is attributed to right lateral shear along the Tibetan Plateau northeastern margins. [ABSTRACT FROM AUTHOR]

The Qilian Shan, located on the northeastern edge of the Tibetan Plateau, shares similar topographic features with Tibet marked by a flat upland plateau flanked by highly-dissected steep margins. Therefore, the research on the topographic evolution of the Qilian Shan will not only facilitate the understanding of its uplift history but also shed light on the uplift process and formation mechanism of the Tibetan Plateau. In this study, we carried out (U Th)/He and cosmogenic 21Ne analyses on the granitoid peneplain of the Central Qilian Shan, and our results indicate that the Qilian Shan has inherited a Cretaceous low-relief landscape that formed at low elevation. Apatite (U Th)/He cooling ages and 21Ne-inferrred erosion rates record a slow exhumation process with a rate of ∼15 ± 5 m/Myr of the peneplain from the middle Cretaceous to present. Combined with previous studies on the Cenozoic tectonics of the Qilian Shan, we infer that the prolonged stable landscape of the Central Qilian Shan has been elevated to high elevation along the boundary thrusting by coeval crustal thickening of the Qilian Shan, to form a flat upland plateau. Whereas, compared to the Central Qilian block, the southern and northern Qilian Shan have relatively weak lithosphere, which consist of accretionary systems. The strong thrusting of the boundary faults enabled the southern and northern Qilian Shan uplifted to form highly-dissected margins flanking the flat interior plateau. In this context, our study may provide an analog for understanding the uplift mechanism of the Tibetan Plateau. • The Central Qilian Shan has inherited a Cretaceous low-relief landscape. • A slow exhumation rate of 15 m/Myr since middle Cretaceous revealed by AHe analyses. • Cosmogenic 21Ne analyses provide consistent erosion rates of ∼3–16 m/Myr. • The Central Qilian Shan has been elevated to high elevation by an entire uplift mode. • We provide an analog for understanding the uplift mechanism of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]