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Grazing exclusion is one of the primary management practices used to restore degraded grasslands on the Tibetan Plateau. However, to date, the effects of long-term grazing exclusion measures on the process of restoring degraded alpine meadows have not been evaluated. In this study, moderately degraded plots, in which the vegetation coverage was approximately 65% and the dominant plant species was Potentilla anserina L, with grazing exclusion for 2 to 23 years, were selected in alpine meadows of Haibei in Qinghai-Tibet Plateau. Plant coverage, plant height, biomass, soil bulk density, saturated water content, soil organic carbon (SOC) and total nitrogen (TN) were evaluated. The results were as follows: (1) With increased grazing exclusion duration, aboveground biomass and total saturated water content at 0–40 cm depth, the average SOC and TN contents in moderately degraded alpine meadows increased as a power function, and the plant height increased as a log function. (2) The average soil bulk density at 0–40 cm depth first decreased and then increased with increasing grazing exclusion duration, and the minimum value of 0.90 g·cm−3 was reached at 15.23 years. The plant coverage, total belowground biomass at 0–40 cm depth, total aboveground and belowground biomass first increased and then decreased, their maximum values (80.49%, 2452.92 g·m−2, 2891.06 g·m−2) were reached at 9.41, 9.46 and 10.25 years, respectively. Long-term grazing exclusion is apparently harmful for the sustainable restoration of degraded alpine meadows. The optimal duration of grazing exclusion for the restoration of moderately degraded alpine meadows was 10 years. This research suggests that moderate disturbance should be allowed in moderately degraded alpine meadows after 10 years of grazing exclusion. [ABSTRACT FROM AUTHOR]

The northeastern Tibetan Plateau exhibits steep topography and strong internal or external dynamic geological effect and is frequently subjected to strong earthquakes and heavy rainfall. The geological evolution has resulted in a wide distribution of ancient landslides, which has become a hotspot for studying ancient landslide formation and reactivation. In recent decades, several ancient landslides on both banks of the Longwu River, Qinghai Province, China were reactivated, causing serious economic losses and casualties. This study conducted remote sensing interpretation and ground surveys on these ancient landslides. Totally 59 ancient landslides were identified, and the formation mechanism, evolution process, and resurrection mechanism of the Longwu Xishan No.2 ancient landslide were analyzed by means of a detailed field geological survey, drilling, and series of experimental tests such as the particle size distribution test, the X-ray diffraction test and the mechanical properties test. The results show that the formation of these ancient landslides is closely associated with the uplift of the Tibetan Plateau and the erosion of the Longwu River. Firstly, the intermittent uplift of the Tibetan Plateau lead to the diversion and downcutting of the Longwu River basin, which forms the alternate slope topography with steep and slow slopes, thereby providing favourable topography and slope structure conditions for the formation of landslides. Secondly, 34.5% clay-mineral content in the Neoproterozoic mudstone with 32.7% particle size less than 0.005 mm, and the corrosion and softening effects of the Neogene mudstone with high clay mineral content under the erosion of water provides favourable material conditions for the formation of landslides. Thirdly, rainfall and human activities are the primary triggering factors for the revival of this ancient landslide group. It is revealed that the evolution process of the ancient landslides on both banks of the Longwu River can be divided into five stages namely tectonic rapid uplift slope formation, river erosion creep-sliding deformation, slope instability critical status, landslide failure-movement-accumulation, and slope reactivation under rainfall erosion and engineering excavation. [ABSTRACT FROM AUTHOR]

Large-scale intra-continental strike-slip faults provide the pathways for groundwater circulation and the release of CO 2 -rich fluids through thermal springs, which is a significant type of deep CO 2 emissions into the atmosphere and hydrosphere. India-Asia collision created numerous strike-slip faults and thermal springs in the Tibetan Plateau and adjacent regions, but their CO 2 origins and fluxes are still not well understood. Here, we present a quantitative study on CO 2 emissions from thermal springs in the Karakoram fault system (KKFS) and adjacent regions, western Tibetan Plateau, with the aim of revealing the origins of CO 2 -rich fluids and estimating the dissolved and gaseous CO 2 fluxes. Hydrogen and oxygen isotopic data show that the geothermal waters were recharged by local precipitation (e.g., rainfall and snow-melt water) and experienced variable degrees of water-rock interaction, giving rise to the dominant Na–HCO 3 type and minor Na–Cl and Ca–HCO 3 type waters discharging from thermal springs. Spatially, the thermal springs within or close to the KKFS (Group 1 and Group 2) have larger circulation depths of 1.3–5.1 km, while those away from the KKFS (Group 3) exhibit shallow (0.6−0.8 km) groundwater circulation. Mass balance calculations reveal high deeply-sourced carbon inputs (60.4−94.3%) to dissolved inorganic carbon (DIC) of the Group 1 and Group 2 samples, while the Group 3 samples have higher shallow carbon contributions (50.4−60.9%) to DIC via dissolution of carbonate and organic carbon. This is consistent with higher Δ14C DIC values (−788.6‰ to −692.1‰) in Group 3 samples and the lack of radioactive 14C in Group 1 and Group 2 samples (Δ14C DIC = −999.9‰ to −985.9‰). Based on chemical compositions and fluxes of spring water and bubbling gases, the total CO 2 output from thermal springs (including dissolved and gaseous CO 2) in the KKFS is estimated to be ∼2332 t a−1, in which the endogenic carbon such as metamorphic CO 2 accounts for ∼1863 t a−1. Our results provide the first estimate of deep CO 2 flux for the KKFS and would contribute to a better understanding of active CO 2 emissions facilitated by strike-slip faulting processes in continental collision zone. • We studied CO 2 origins and fluxes of thermal springs in Karakoram fault system. •Water-rock interaction is more evident for thermal springs of the Karakoram fault. •Deep and shallow carbon sources are discriminated for dissolved inorganic carbon. •Thermal springs of the Karakoram fault release ∼2332 t a−1 CO 2 to Earth's surface. [ABSTRACT FROM AUTHOR]

[Display omitted] • A south-to-north sampling profile of thermal springs in Sangri-Cona rift (SCR) • Magmatic fluid inputs are identified in geothermal systems of the central SCR. • Geochemical evidence for magmatic fluids agrees with magnetotelluric results. • Geothermal systems are related to orogenic extension and upwelling of crustal melts. Fault-controlled geothermal systems in the Himalayan-Tibetan orogen could receive heat and material from deep-seated magmas due to crustal anatexis in orogenic settings. The near N-S trending rifts in southern Tibetan Plateau host abundant geothermal systems but potential role of residual magmas remains less constrained. Here, we evaluate magmatic contributions to geothermal systems in Sangri-Cona rift (SCR), the youngest rift in southern Tibetan Plateau, based on chemical and isotopic compositions of thermal waters from a south-to-north sampling profile. Our results show that the thermal springs in the central SCR have significant inputs from magmatic fluids, which account for high B concentrations and positive shift in δ18O H2O , while those in the southern and northern SCR are dominated by recharge of meteoric water. Water-rock interaction constrained by 87Sr/86Sr, hydrochemistry, and geothermometry results, suggests a hotter or deeper groundwater circulation path beneath central SCR than that of the southern and northern SCR. The identified magmatic fluid inputs, higher reservoir temperature, and higher degrees of water–rock interaction in the central SCR agree well with the presence of high conductivity anomalies at crustal depths of ∼ 10–30 km revealed by magnetotelluric surveys. Our findings provide geochemical evidence for the impact of lithospheric extension and associated geological and geophysical expressions (e.g., extension-induced exhumation of genesis domes that recorded crustal anatexis and upwelling of partially molten crustal channel flows) on modern geothermal systems in collisional orogens. [ABSTRACT FROM AUTHOR]