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Pollution usually accumulates on the surface of the insulator rapidly on high‐speed electric multiple units (EMUs) under operation condition, and the flashover can occur frequently, especially when the EMUs is running on a high‐altitude line. To solve the problem, this paper proposes the calculation method of insulator withstand voltage under the condition of non‐uniform fouling distribution of high‐speed airflow based on the characteristics of high altitude of Lanzhou‐Xin Line in China, and gives the design and test verification of insulator support insulator for 3500‐km altitude. The design and test verification of the supporting insulator of the rolling stock applicable to 3500 km altitude are presented. The result shows that the insulator should be reliable operation on 4430‐km high altitude area if the insulator structure height is 430 mm, the creep distance is 1250 mm. The anti‐pollution performance is fine in high‐speed wind if the radiuses of the large and small shed of the insulator are 196 and 145 mm, respectively, and the shed spacing is 45 mm. The 50‐Hz withstand voltage of the developed insulator is 131 kV and the light impulse voltage is 228 kV which is suitable for lines running on 3500 m. This research provides a theoretical basis and data to support the safety of high‐speed rolling stock in high‐altitude areas. [ABSTRACT FROM AUTHOR]

This paper presents our efforts to characterize the candidate landing region (109°–133°E, 23°–30°N) for Tianwen‐1, China's first mission to Mars, in terms of engineering safety and scientific significance. Topographic analysis reveals that the region has a low elevation around −4,230 m, and 98% of the region have slopes smaller than 8°. The geomorphological mapping and analysis show that the region has an average crater density of about 28 craters (≥200 m in diameter) per 100 square kilometers, with several clusters of high crater densities distributed around the center of the region. There are also pitted cones distributed mainly in the southern part of the region, with a density of approximately 6.6 cones per 100 square kilometers in specific local areas. The region has rock abundances ranging from 1% to 23%, with local clusters of low and high rock abundances. The region comprises four main geological units, including a lowland unit formed in the Late Hesperian and a volcanic unit formed in the Amazonian and Hesperian period. Their specific surface ages are estimated through the analysis of crater size‐frequency distribution. Combining the engineering constraints on surface slopes, crater density, cone density, and rock abundance, a hazard map of the candidate landing region is generated for landing site evaluation and safety assessment. Based on the results, we further discuss the potential scientific outcomes from the exploration in this region. The findings will be helpful for the mission planning and maximization of the scientific return from Tianwen‐1, and complement existing Martian scientific research. Key Points: Topographic, geomorphological, and geologic characterization of the candidate landing region of Tianwen‐1A hazard map of the region combining engineering constraints on slopes, crater density, cone density, and rock abundanceTwo local areas in the region are highlighted as potential landing sites for their low hazard and scientific significance [ABSTRACT FROM AUTHOR]

Previous theoretical simulations showed the generation of double‐layer structures of E‐region field‐aligned irregularities (FAIs). In this study, we report the double‐layer structures of E‐region FAIs observed by an all‐sky radar at low latitude Ledong (18.4°N, 109°E), China. These FAIs appeared at the altitudes ∼90 and 110 km respectively. Both layers displayed quasi‐periodic patterns with synchronized spatial features, that is, being manifested as spatially separated patches or wavelike structures over similar longitudes at the two layers simultaneously. The neutral wind observations revealed the existence of wind shears at two separated altitudes where the double FAI layers occurred. The two wind shears created two vertically separated sporadic E layers and possibly drove the generation of the double‐layer FAIs via gradient drift instability. The synchronized spatial features of the FAIs at the two layers could be modulated by gravity waves. Plain Language Summary: The E‐region field‐aligned irregularities (FAIs) were observed usually in a form of single layer. Due to the limited field of view of narrow‐beam radars which were traditionally employed for observing ionospheric irregularity, the spatial morphology and evolution of E‐region FAIs in a small region were resolved. Owing to the recently developed capability of all‐sky radars in observing E‐region irregularities, the spatial features of E‐region irregularities over a larger zonal region up to hundreds of kilometers in the horizontal plane can be derived. Further, the spatial features of E‐region irregularities in the vertical direction can be unambiguously determined. Utilizing an all‐sky radar at low latitude Ledong, China, a case of double‐layer structures of E‐region FAIs, which occurred at ∼90 and 110 km altitudes respectively, was observed. The double layers of FAIs spanned a zonal coverage ∼250 km, showing as synchronized spatially separated quasi‐periodic patches or wavelike structures in two layers. Especially, the wavelike structures synchronized in the two layers could provide solid evidence for the crucial role of gravity waves in modulating E‐region irregularities. In combination with the collocated ionosonde Es and neutral wind observations, the physical mechanisms responsible for the generation of the double‐layer E‐region FAIs were discussed. Key Points: Double layer structures of E‐region field‐aligned irregularity (FAI) were observed at low latitude by an all‐sky radarBoth layers of FAIs were quasi‐periodic type and synchronously manifested as spatially separated patches or wavelike structuresThe double‐layer FAIs were likely generated by wind shear driven gradient drift instability and modulated by gravity waves [ABSTRACT FROM AUTHOR]

Seed dormancy contributes greatly to successful establishment and community stability and shows large variation over a continuous status scale in mountain ecosystems. Although empirical studies have shown that seed dormancy status (SDS) is shaped by elevation and phylogenetic history in mountain ecosystems, few studies have quantified their combined effects on SDS. Here, we collected mature seeds from 51 populations of 11 Impatiens species (Balsaminaceae) along an elevational gradient in the Gaoligong Mountains of southwest China and estimated SDS using mean dormancy percentage of fresh seeds germinated at three constant temperatures (15, 20, and 25°C). We downloaded 19 bioclimatic variables from WorldClim v.2.1 for each Impatiens population and used internal transcribed spacer (ITS), atpB‐rbcL, and trnL‐F molecular sequences from the GenBank nucleotide database to construct a phylogenetic tree of the 11 species of Impatiens. Logistic regression model analysis was performed to quantify the effects of phylogeny and environment on SDS. Results identified a significant phylogenetic SDS signal in the Impatiens species. Furthermore, elevation and phylogeny accounted for 63.629% of the total variation in SDS among the Impatiens populations. The best logistic model indicated that temperature was the main factor influencing variation in SDS among the Impatiens species, and model residuals were significantly correlated with phylogeny, but not with elevation. Our results indicated that seed dormancy is phylogenetically conserved, and climate drives elevational patterns of SDS variation in mountain ecosystems. This study provides new insights into the response of seed plant diversity to climate change. [ABSTRACT FROM AUTHOR]

East Yunnan‐Kweichow Plateau is rich in biodiversity in China. Complex geographical and climatic conditions and rich bird resources made this area an ideal system for studying the spatial distribution mechanism and influencing factors of birds, which were still unknown. Bird community data from 37 sites in this region were collected, including 505 bird species and 164 species of resident passerine bird, were extracted for analysis. The taxonomic diversity, phylogenetic diversity, functional diversity (FD), and community structure index were calculated. Ordinary least square (OLS), spatial autoregressive models (SAR), and structural equation model (SEM) were used to explore the relationship between bird diversity index and environmental factors which were used to describe the habitat conditions of birds. Results indicated that species richness (SR), phylogenetic diversity (PD), and FD have similar distribution patterns and are mainly affected by vascular plant species richness, habitat area, and vertical altitude difference. The phylogenetic and functional structure of bird community changed in both longitude and latitude direction, and the phylogenetic structure of community was dispersed in the west and clustered in the east, significantly related to habitat area, and vertical altitude difference, the functional structure was dispersed in all sites, significantly related to average annual precipitation. The community in the west and south of the East Yunnan‐Kweichow Plateau is mainly driven by interspecific competitive, while the process in the east and north is mainly driven by environmental filtration. Distribution pattern of bird diversity was caused by the comprehensive action of various habitat factors which were mainly related to food availability and habitat heterogeneity. For maintaining the living space of birds, the protection of urban parks, wetland parks, campuses, and other urban green spaces is as important as national and provincial nature reserves. Revealing the construction mechanism and main influencing factors of bird communities in different areas is conducive to targeted protection work. [ABSTRACT FROM AUTHOR]

Summary: Identifying the contours and correlates of species turnover is central to understanding the nature of biogeographical regions. The Hengduan Mountains region of south‐central China (HMR) is well known for its high diversity of plants, but its boundaries and internal floristic structure are poorly understood, especially in relation to geographical and environmental factors.With data on occurrences and elevational ranges of seed plants across the HMR and adjacent areas of the greater Qinghai‐Tibet Plateau, we identified motifs (distinct species assemblages) by Grade of Membership models, and characterized relative contributions of geography, elevation, and climate to their spatial patterns.Motifs segregate primarily by latitude, elevation, and correlated environmental variables, most sharply across the tropical‐temperate divide. Secondarily, they segregate by longitude and geographical features, and reveal a novel divide across the Jinsha River. A core set of motifs corresponds to previous delineations of the HMR.The HMR biodiversity hotspot is more a mosaic of floristic elements than a cohesive entity. Grade of Membership models effectively reveal the geographical contours of biotic structure, and are a valuable new tool for biogeographical analysis. See also the Commentary on this article by Muellner‐Riehl & Favre, 232: 964–966. [ABSTRACT FROM AUTHOR]

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