Search

Recently, the Tibetan Plateau (TP) has experienced dramatic climate change, which influence atmospheric and hydrological cycles. The understanding of surface water dynamics is essential to further investigate the water balance and the hydrologic cycle in this region. In this study, we used all available Landsat Surface Reflectance imagery that generated Modified Normalized Difference Water Index (MNDWI) overlapped the TP in time-series for 1996–2019. We detected the annual changes in surface water using the LandTrendr algorithm on the Google Earth Engine (GEE), and examined impact factors on surface water area dynamics. During 1996–2019, the area of 17,065 km2 had changed from land to water body and 3511 km2 had changed from water to land in the entire TP. The drivers of surface water change are spatially heterogeneous. Precipitation is a main cause of surface water variability in the central, northern and eastern parts of the TP. Meanwhile, temperature is the dominant factor affecting the western and southern parts of the TP. Our results proved that LandTrendr could be applied to monitor surface water changes over larger spatial and temporal scales. In conclusion, our study focus on understanding the process of climate change and the hydrological cycle across the TP. [ABSTRACT FROM AUTHOR]

The Bangong–Nujiang Suture Zone (BNSZ), located in the central Tibetan Plateau, experienced a Late Mesozoic transition from oceanic closure to continent–continent collision. Based on sandstone-composition analyses, U-Pb detrital-zircon dating and structural observations, we determined that this transition occurred coeval with the accretion of the Lhasa Terrane to Eurasia. According to our newly observed stratigraphic and geochronological data, we conclude the following: (1) the Upper Triassic-Lower Jurassic Muggar Gangri Group was mainly derived from the Qiangtang Terrane; (2) the Shamuluo Formation composed of Upper Jurassic-Lower Cretaceous shallow marine strata was sourced from both the Qiangtang Terrane and recycled Muggar Gangri Group; (3) the Lower Cretaceous (~125–110 Ma) Duoni Formation shows both Lhasa and Qiangtang detrital zircon fingerprints, indicating closure of the Bangong–Nujiang Ocean at ~120 Ma; and (4) the Upper Cretaceous Abushan Formation is a suite of intramontane molasse deposited after the Qiangtang–Lhasa collision. Therefore, these sedimentary strata record the transition from oceanic closure to continent–continent collision from 125 to 90 Ma within the central BNSZ. Moreover, based on relationships among strata distributions and thrust locations, we propose that thrust movements propagated southward during this transition and controlled sedimentary basin deposition. The Late Mesozoic tectonic transition within the BNSZ occurred well before the India-Asia collision and hence profoundly influenced the Cenozoic formation of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Species distribution is often closely associated with soil nutrients in terrestrial ecosystem. In contrast to most manipulated N (nitrogen) experimental studies, there are few observation experiments examining the distribution of species or functional groups along a natural soil N gradient. Alpine meadows with higher soil spatial heterogeneity at fine scale, which have a large gradient in soil N gradient, provides an ideal system to examine the distribution of species or functional groups. Here we used redundancy analysis (RDA) to examine the relationships between soil and plant properties in northeast of Qinghai-Tibet Plateau over two years. The results showed the relative biomass of forbs increased, while those of legumes and grasses decreased with the soil N availability. This suggests that legumes and grasses had stronger tolerance to infertile soils than forbs, which may due to the N-fixed for legumes and high nutrient use efficiency for grasses. Furthermore, the positive significant relationships between the percentage of legumes biomass and N: P (phosphorus) ratio were found in the whole community and non-legumes, confirming the presence of legumes improved the vegetation N status even for non-legumes. [ABSTRACT FROM AUTHOR]

Conflicting interpretations of the > 500 km long, east-west-trending Qiangtang metamorphic belt have led to very different and contradicting models for the Permo- Triassic tectonic evolution of central Tibet. We define two metamorphic events, one that only affected pre-Ordovician basement rocks and one subduction-related Triassic highpressure metamorphism event. Detailed mapping and structural analysis allowed us to define three main units that were juxtaposed due to collision of the north and south Qiangtang terranes after closure of the Ordovician-Triassic ocean that separated them. The base is formed by the Precambrian-Carboniferous basement, followed by nonmetamorphic ophiolitic mélange containing mafic rocks that range in age from the Ordovician to Middle Triassic. The top of the sequence is formed by strongly deformed sedimentary mélange that contains up to > 10 km size rafts of both unmetamorphosed Permian sediments and highpressure blueschists.We propose that the high-pressure rocks were exhumed from underneath the south Qiangtang terrane in an extensional setting caused by the pull of the northward subducting slab of the Shuanghu-Tethys. Highpressure rocks, sedimentary mélange and margin sediments were thrust on top of the ophiolitic mélange that was scraped off the subducting plate. Both units were subsequently thrust on top of the south Qiantang terrane continental basement. Onset of Late Triassic sedimentation marked the end of the amalgamation of both Qiangtang terranes and the beginning of spreading between Qiantang and north Lhasa to the south, leading to the deposition of thick flysch deposits in the Jurassic. [ABSTRACT FROM AUTHOR]