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The upper Yellow River basin over the Tibetan Plateau (TP) is an important ecological barrier in northwestern China. Effective LULC products that enable the monitoring of changes in regional ecosystem types are of great importance for their environmental protection and macro-control. Here, we combined an 18-class LULC classification scheme based on ecosystem types with Sentinel-2 imagery, the Google Earth Engine (GEE) platform, and the random forest method to present new LULC products with a spatial resolution of 10 m in 2018 and 2020 for the upper Yellow River Basin over the TP and conducted monitoring of changes in ecosystem types. The results indicated that: (1) In 2018 and 2020, the overall accuracy (OA) of LULC maps ranged between 87.45% and 93.02%. (2) Grassland was the main LULC first-degree class in the research area, followed by wetland and water bodies and barren land. For the LULC second-degree class, the main LULC was grassland, followed by broadleaf shrub and marsh. (3) In the first-degree class of changes in ecosystem types, the largest area of progressive succession (positive) was grassland–shrubland (451.13 km2), whereas the largest area of retrogressive succession (negative) was grassland–barren (395.91 km2). In the second-degree class, the largest areas of progressive succession (positive) were grassland–broadleaf shrub (344.68 km2) and desert land–grassland (302.02 km2), whereas the largest areas of retrogressive succession (negative) were broadleaf shrubland–grassland (309.08 km2) and grassland–bare rock (193.89 km2). The northern and southwestern parts of the study area showed a trend towards positive succession, whereas the south-central Huangnan, northeastern Gannan, and central Aba Prefectures showed signs of retrogressive succession in their changes in ecosystem types. The purpose of this study was to provide basis data for basin-scale ecosystem monitoring and analysis with more detailed categories and reliable accuracy. [ABSTRACT FROM AUTHOR]

[Display omitted] • An ecosystem health-risk-services framework is developed to assess ecological security. • The credibility and reasonability of the assessment results are verified. • The ecological security of the GAPR was dominated by medium and above security levels. • The gravity centers of ecological security levels have changed from 2000 to 2020. Ecological security is a critical guarantor of human security and indeed human survival and is closely associated with sustainable development. Yet exploration of ecological security assessment in alpine pastoral regions is lacking, and many studies have failed to perform validation analyses on ecological security assessment results, weakening the reliability of their assessment results. In this study, an ecosystem health-risk-services framework is developed to assess the ecological security of the Gannan alpine pastoral region (GAPR) on the northeastern Tibetan Plateau from 2000 to 2020. Then, the remote sensing ecological index (RSEI) and high-resolution images are then introduced to verify and compare the results' reliability. Our study results indicate: (1) The assessment framework can better reflect the actual ecological security state in GAPR, and the correlation coefficient (R 2) of the comprehensive ecological security index (CESI) and RSEI is between 0.426 and 0.555 (p < 0.001). (2) The CESI value of GAPR shows a fluctuating and increasing trend from 2000 to 2020, with a spatial distribution pattern of high values in the south and low values in the north. The ecological security levels in GAPR are dominated by medium, medium-high and high security levels. (3) The centers of gravity of low and medium-low security levels show a northward movement trend, while that of medium-high and high security levels show a southward movement. Our framework provides a new perspective for ecological security assessment methods, which can be extended to other regions, and the results contribute useful references to decision-makers for socioeconomic development and eco-environmental protection in GAPR. [ABSTRACT FROM AUTHOR]

Seed germination is a crucial stage in the life history of a species because it represents the pathway from adult to offspring, and it can affect the distribution and abundance of species in communities. In this study, we examined the effects of phylogenetic, life history and environmental factors on seed germination of 134 common species from an alpine/subalpine meadow on the eastern Tibetan Plateau. In one-way ANOVAs, phylogenetic groups (at or above order) explained 13.0% and 25.9% of the variance in germination percentage and mean germination time, respectively; life history attributes, such as seed size, dispersal mode, explained 3.7%, 2.1% of the variance in germination percentage and 6.3%, 8.7% of the variance in mean germination time, respectively; the environmental factors temperature and habitat explained 4.7%, 1.0% of the variance in germination percentage and 13.5%, 1.7% of the variance in mean germination time, respectively. Our results demonstrated that elevated temperature would lead to a significant increase in germination percentage and an accelerated germination. Multi-factorial ANOVAs showed that the three major factors contributing to differences in germination percentage and mean germination time in this alpine/subalpine meadow were phylogenetic attributes, temperature and seed size (explained 10.5%, 4.7% and 1.4% of the variance in germination percentage independently, respectively; and explained 14.9%, 13.5% and 2.7% of the variance in mean germination time independently, respectively). In addition, there were strong associations between phylogenetic group and life history attributes, and between life history attributes and environmental factors. Therefore, germination variation are constrained mainly by phylogenetic inertia in a community, and seed germination variation correlated with phylogeny is also associated with life history attributes, suggesting a role of niche adaptation in the conservation of germination variation within lineages. Meanwhile, selection can maintain the association between germination behavior and the environmental conditions within a lineage. [ABSTRACT FROM AUTHOR]