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A brief taxonomic review of the lithosiinid genus Ammathella Volynkin, 2019 is presented. Three new species of the genus Ammathella Volynkin, 2019 are described from Motuo County, southeast Xizang: A. longicornuta S.-Y. Huang, Yin & Volynkin, sp. nov., A. lhoba S.-Y. Huang, Yin & Volynkin, sp. nov., and A. monpa S.-Y. Huang, Yin & Volynkin, sp. nov. A key to the species of the genus is provided. Adults and genitalia of both sexes are illustrated. [ABSTRACT FROM AUTHOR]

Background and aims: An increase in nitrogen deposition is expected to increase the phosphorus-limited primary productivity of grassland ecosystems. However, it remains unclear as to whether the primary productivity of grasslands is co-limited by nitrogen and phosphorus, or only by one or the other. Methods: Nitrogen and phosphorus addition experiments were conducted at an alpine steppe site in North Tibet from 2013 to 2017. The biomass of plant community, the N and P content of plant leaf, soil chemical property, and changes in abundance and function and composition of bacterial and fungal community with N and P treatment were analyzed after five years. Results: Results from analyzing the response ratios of shoot biomass and leaf nitrogen and phosphorus concentrations to nitrogen and phosphorus addition suggested that nitrogen is the main limiting factor for the biomass of alpine steppe. Based on the ratio of nitrogen and phosphorus stoichiometry, plants must increase their phosphorus absorption following nitrogen addition. From the results of a structural equation model, plants and fungi both promoted the activity of phosphatase. The abundance of fungi and the saprotrophic group associated with decomposition increased following nitrogen addition, and more substrate is provided by the plants, which will accelerate the organic phosphorus cycle. These results suggest that the phosphorus deficit of plants owing to nitrogen addition will be alleviated. On the contrary, phosphorus did not limit the biomass, but its addition did increase the absorption of nitrogen by plants. Although the activity of urease was enhanced by soil microbes and plants, there was little substrate for microbes because the plant biomass was limited by nitrogen. Conclusions: The biomass is mainly limited by nitrogen and soil microbes will influence the effect of nitrogen on biomass in alpine steppe. [ABSTRACT FROM AUTHOR]

Eight species of the genus Nephrotoma were previously known to occur in Xizang Autonomous Region. Here, three species are added to the fauna of Xizang. Among them two species, N. beibengensis sp. nov. and N. hanae sp. nov. are described and illustrated as new to science, and one species, N. evittata Alexander, 1935 is recorded from Xizang for the first time. The following four species are redescribed: N. claviformis Yang & Yang, 1987, N. didyma Yang & Yang, 1987, N. nigrohalterata Edwards, 1928, and N. xizangensis Yang & Yang, 1987. A key to the species of Nephrotoma from Xizang is presented. [ABSTRACT FROM AUTHOR]

The Cuobuzha high‐Cr chromitites in the western segment of Yarlung Zangbo Suture Zone of Tibet are mainly hosted in the harzburgites as massive type, which are characterized by high concentrations of platinum group elements (PGE) ranging from 380 to 577 ppb, and low Pd/Ir ratios (<0.1). In mid‐ocean ridge basalts (MORB)‐normalized spidergrams, chromites of the Cuobuzha chromitites are depleted in Al, Ga, V, Mg and Zn, and enriched in Mn and Cr, sharing similar patterns with those of ophiolitic boninites in the Bonin and Thetford Mines. Approximately 20 platinum group mineral (PGM) grains were discovered from the samples, including laurite, erlichmanite, Os‐Fe alloy, cuproiridsite, and irarsite. The PGM assemblages indicate that sulfur fugacity was initially low enough to allow the precipitation of Os‐Fe alloy and increased thereafter, with the fall in temperature. Primary Fe‐Ni and Fe‐Cr alloys, which are stable in a highly reduced environment, occur as inclusions within chromites or clinopyroxenes. Calculated results show that the parental magma has an intimate affinity with boninites. Based on our observations, a model is proposed wherein the Cuobuzha chromitites contain high‐pressure and low‐pressure chromites. Low‐pressure chromites were formed via reaction between boninitic melts and peridotites, during which the high‐pressure chromites hosting highly reduced minerals were mobilized by melts and were reallocated to podiform chromitites. [ABSTRACT FROM AUTHOR]

Four wetland maps for all China have been produced, based on Landsat and CBERS-02B remote sensing data between 1978 and 2008 (1978, 1990, 2000 and 2008). These maps were mainly developed by manual interpretation and validated by substantial field investigation in 2009. Based on these maps, we analyzed the 2008 wetland distribution in China and discussed wetland changes and their drivers over the past 30 years. (i) There were about 324097 km of wetlands in 2008, for which inland marshes or swamps were the most common wetland type (35%), with lakes (26%) second. Most of the wetlands were in Heilongjiang, Inner Mongolia, Qinghai and Tibet, occupying about 55% of the national wetland area. (ii) From 1978 to 2008, China's wetland area continually and significantly decreased, by about 33% based on changes in the wetland map. This was in sharp contrast to the increase in artificial wetlands, which increased by about 122%. Inland marshes accounted for the main loss of total wetlands from 1978 to 2000. From 2000 through 2008, riverine and lacustrine wetlands constituted the main wetland loss. Fortunately however, the rate of wetland loss decreased from 5523 to 831 km/a. (iii) The change ratio of lost natural wetlands (including inland and coastal wetlands) to non-wetlands has decreased slightly over the past 30 years. From 1978 to 1990, nearly all natural wetlands (98%) lost were transformed into non-wetlands. However, the ratio declined to 86% from 1990 to 2000, and to 77% from 2000 to 2008. (iv) All Chinese provinces were divided into three groups according to patterns of wetland changes, which could relate to the driving forces of such changes. Tibet was completely different from other provinces, as it was one representative example in which there was a net wetland increase, because of global warming and decreased human activity since 1990. Increased economic development caused considerable wetland loss in most eastern provinces, and artificial wetlands increased. [ABSTRACT FROM AUTHOR]

The identification of plant species in alpine steppes of Northern Tibet is of great significance for revealing community structures and for monitoring vegetation degradation and restoration from remote sensing images. Plants in the alpine steppe of Northern Tibet are short, sparse, and highly heterogeneous in spatial distribution. This peculiarity makes the plant species identification here much more difficult than the identification of plants with high spatial homogeneity. We aimed to explore the potential of close-range hyperspectral imaging for plant species identification in alpine steppe under field conditions. Specifically, we assessed which spectral bands are effective and which classification methods are suitable for plant species identification. A close-range hyperspectral image of grassland in Nagqu, Tibet were acquired in August 2018. Four methods, including derivatives, continuum removal, spectral indices, and principal components were used to enhance the differences in spectral characteristics between plant species. Then, two band selection methods, including Mahalanobis distance and variable importance evaluations based on a random forest (RF) were used to reduce dimensionality and select indicators beneficial for identifying grass species. Four datasets were constructed based on those indicators and were used as the input data for four classifiers, support vector machine (SVM), RF, artificial neural network (ANN), and spectral angle mapper (SAM). We found that (1) bands selected using Mahalanobis distance and variable importance evaluation method showed that the red bands, red edge bands, and spectral indices were important for plant species identification; (2) among the four classifiers, the ANN classifier had the highest overall classification accuracy on Dataset 3 of the reflectance images, which was 94.73%, and the Kappa coefficient was 0.93; (3) the machine learning algorithms RF and ANN performed well for identifying plant species, with an overall accuracy more than 91.59% and kappa coefficient above 0.89. These results suggest that close-range hyperspectral image and machine-learning classifiers, such as RF and ANN, can be used to effectively identify plant species in alpine steppe. • Grass species identification at the level of individuals • Close-range hyperspectral images can be used for grass species identification in alpine steppe. • The machine learning algorithms RF, and ANN performed well at plant species recognition. • Red bands, red edge bands, and spectral indices were important for plant species identification. • Based on RF method, the overall accuracy of plant species identification exceeds 93%. [ABSTRACT FROM AUTHOR]

The world's largest alpine pastures are found on the Tibetan Plateau, where considerable climate changes and human impacts have been experienced. Identifying their contributions to terrestrial productivity is essential if we are to adapt to, or mitigate the effects of, climate change. In this work, we begin by showing how the current warming and wetting of the climate over the last three decades has favored plant growth, as consistently captured by satellite observations and 15 models. However, the interactions between climate factors explain less of the variation in greenness observed by satellites after the 2000s, implying non-climatic influences. Next, we show that there is a significant negative impact of livestock grazing on pasture greenness, especially in peak summer. Official statistics across 72 counties verify these negative impacts, especially in poorer pastures with a higher density of grazing livestock. The variation in grazing density has a stronger negative effect on vegetation growth during the early part of the growing season after the 2000s, as compared with that before the 2000s. We found a compensatory effect of grazing and climate on alpine grassland growth, and the grazing regulates the response of vegetation greenness to climate change by modulating the dependency of vegetation growth on temperature. Thus, we suggest there is a weakening influence of climate on the greenness of alpine pastures, largely due to a strengthening influence of management, which should be considered by both the scientific community and policymakers. Tibetan Plateau is home to world's largest alpine pastures. In this study, we found that the interactions between climate factors less explain the variation in greenness observed by satellites after the 2000s. We then show that the variation in grazing density even has a stronger negative effect on vegetation growth during the early part of the growing season after the 2000s, compared with that before 2000s. We further reveal that the grazing regulates apparent response of vegetation greenness to climate change, by modulating the dependency of vegetation greenness on temperature variation. The weakening influence of climate on the greenness of alpine pastures and a strengthening influence of human management should be considered by both the scientific community and policy makers. Image 1 • Satellite observations and 15 models capture the greening of alpine pastures in Tibet. • Models fail to capture the nonlinear variation in greenness after the 2000s. • Grazing negatively affect alpine pasture greenness across 72 counties in Tibet. • Variation in grazing density play a stronger role on regulating vegetation growth than before. • Climate influence is weakening while human influence is strengthening on Tibetan pastures. [ABSTRACT FROM AUTHOR]

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The Xigaze ophiolite in the central Yarlung Zangbo suture zone (southern Tibet) provides evidence of the tectonic processes that formed the Neotethyan Ocean between the Indian and Eurasian plates. In this study, we present zircon U Pb geochronological, mineralogical, and geochemical data for mafic rocks from the Xigaze ophiolite to determine their petrogenesis and tectonic environment. The crustal section of the Xigaze ophiolite includes mainly gabbro lenses, amphibolite dikes, dolerite sills or dikes, and basaltic lavas. The absence of a well-developed gabbroic crust and sheeted dike complexes in the ophiolite indicates slow to ultraslow-spreading conditions and a heterogeneous structure of the oceanic lithosphere, which is not atypical for layered ophiolites. Zircons from the amphibolite and dolerite dike reveal crystallization ages of 125.0 ± 1.8 Ma to 123.8 ± 1.3 Ma, respectively. Geochemically, all mafic rocks have mid-ocean ridge basalt (MORB)-like affinities with enrichment in large ion lithophile elements (LILEs, U) relative to high field strength elements (HFSEs, Nb, Ta and Ti) and light rare earth elements (LREEs). They also exhibit high εNd(t) values ranging from +8.4 to +8.8 at 206Pb/204Pb = 16.75–17.64. Moreover, chromite and clinopyroxene grains from the mafic rocks have a wide compositional spectrum and are mainly plotted in the supra-subduction zone (SSZ) fields. These features indicate that MORB-like magmatism was triggered by decompression melting of the upwelling asthenospheric mantle with minor mass transfer from the subducting slab. The Xigaze ophiolite lacks boninite, high‑magnesium andesites, island arc tholeiites, and calc-alkaline lavas, which indicates that it is incompatible with the complete Izu-Bonin-Mariana forearc sequence. Combined with previous studies, we speculate that the Xigaze ophiolite represents an ancient SSZ-type oceanic lithosphere formed in the Gangdese forearc during the Early Cretaceous, and the upper plate extension is linked to the southward retreat and rollback of the Neotethyan slab. Thus, the Xigaze and other Neotethyan SSZ ophiolites with no systematic change in composition with stratigraphic age provide new insights into the diversity of melt evolution in the forearc crust. [Display omitted] • Amphibolite and dolerite dikes in the Xigaze ophiolite were formed during the Early Cretaceous. • The mafic rocks were derived from upwelling asthenosphere with minor slab input. • The Xigaze ophiolite originated from the Gangdese forearc setting. • The SIR model appears likely to be oversimplified for variable forearc ophiolites. [ABSTRACT FROM AUTHOR]