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Drought is one of the most complex and least-understood environmental disasters that can trigger environmental, societal, and economic problems. To accurately assess the drought conditions in the Yellow River Basin, this study reconstructed the Land Surface Temperature (LST) using the Annual Temperature Cycle (ATC) model and the Normalized Difference Vegetation Index (NDVI). The Temperature Condition Index (TCI), Vegetation Condition Index (VCI), Vegetation Health Index (VHI), and Temperature-Vegetation Drought Index (TVDI), which are four typical remote sensing drought indices, were calculated. Then, the air temperature, precipitation, and soil moisture data were used to evaluate the applicability of each drought index to different land types. Finally, this study characterized the spatial and temporal patterns of drought in the Yellow River Basin from 2003 to 2019. The results show that: (1) Using the LST reconstructed by the ATC model to calculate the drought index can effectively improve the accuracy of drought monitoring. In most areas, the reconstructed TCI, VHI, and TVDI are more reliable for monitoring drought conditions than the unreconstructed VCI. (2) The four drought indices (TCI, VCI, VH, TVDI) represent the same temporal and spatial patterns throughout the study area. However, in some small areas, the temporal and spatial patterns represented by different drought indices are different. (3) In the Yellow River Basin, the drought level is highest in the northwest and lowest in the southwest and southeast. The dry conditions in the Yellow River Basin were stable from 2003 to 2019. The results in this paper provide a basis for better understanding and evaluating the drought conditions in the Yellow River Basin and can guide water resources management, agricultural production, and ecological protection of this area.

The ancient Qin-Shu roads corridor is one of the important cultural main corridors in China. Throughout China’s long historical and cultural evolution, today’s ancestors created a rich intangible cultural heritage along this route. Studying its intangible cultural heritage has important theoretical and practical significance for the protection and innovation of cultural heritage in this region. The purpose of this study is to analyze the spatial and temporal distribution characteristics of intangible cultural heritage along the ancient Qin-Shu roads and explore the main factors affecting its distribution. The nearest neighbor index, kernel density estimation, standard deviation ellipse, location entropy, buffer analysis and other methods were used. The results show that (1) The types of intangible cultural heritage of the ancient Qin-Shu roads are expressed in three echelons. Traditional handicrafts are the most numerous, folk custom and traditional music are the second most numerous, the other categories of ICH are third in quantity overall, among which traditional medicine and sports recreation competition are the scarcest. (2) The overall spatial distribution of intangible cultural heritage along the ancient Qin-Shu roads shows an agglomeration distribution. Its distribution pattern places the central cities (Xi'an, Chengdu and Chongqing) at the core, gradually spreading out and decreasing in density as it reaches peripheral districts and counties. There are significantly differ in the core areas of different types of intangible cultural heritage. (3) In the process of historical development, the intangible cultural heritage of the ancient Qin-Shu roads demonstrated an overall change pattern of “three rising and three falling”. That is, during Qin and Han Dynasties, Sui, Tang and Five Dynasties, and Ming and Qing Dynasties, culture flourished, while in Wei, Jin, Southern and Northern Dynasties, Song and Yuan Dynasties, modern times culture developed slowly. The overall trajectory of the center of gravity of intangible cultural heritage shifted from the northeast to the southwest. (4) Natural and human factors, such as topography, climate, transportation, traditional villages and population evolution, have an important impact on the spatial pattern of the intangible cultural heritage of the ancient Qin-Shu roads. The results of this study provide a useful reference for the theoretical research and practical management of intangible cultural heritage.

As the mainstream and trend of urban development in China, deeply exploring the spatiotemporal patterns and influencing mechanisms of ecosystem service value in the Yangtze River Delta urban agglomeration is of great significance for achieving sustainable development goals in urban agglomerations. This paper uses the normalized difference vegetation index and net primary productivity as dynamic adjustment factors to measure the ecosystem service value of the Yangtze River Delta urban agglomeration and analyze its spatiotemporal evolution characteristics. Furthermore, a panel quantile regression model is constructed to explore the response differences of ecosystem service value at different levels to various influencing factors. The results show that: (1) From 2006 to 2020, the ecosystem service value of the Yangtze River Delta urban agglomeration decreased by 37.086 billion yuan, with high-value areas mainly concentrated in the southern part of the urban agglomeration. (2) The value structure of various land type ecosystems and primary ecosystem sub-services in the Yangtze River Delta urban agglomeration is stable. (3) The number of grid units with reduced ecosystem service value is continuously increasing, mainly distributed in the eastern coastal areas. (4) The degree of interference of various types of land on ecosystem service value varies, and the response of ecosystem service value at different levels to the same influencing factor also shows heterogeneity. In summary, exploring the spatiotemporal patterns of ecosystem service value in the Yangtze River Delta urban agglomeration and analyzing its influencing mechanisms is conducive to adjusting the intensity of human utilization and protection methods of ecosystems, which is of great significance for enhancing the value of ecosystem products in urban agglomerations.

Sports Intangible Cultural Heritage (SICH) serves as both a vital testament to the shared cultural roots of the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) and a treasured resource for fostering a collaborative, culturally enriched Bay Area. Combining field surveys and GIS spatial analysis, and adopting the methods of the nearest neighbor index, geographic concentration index, imbalance index, kernel density estimation and geographical detectors, the study aims to analyze the characteristics of the spatial distribution of the 264 SICH projects in the GBA, and to explore the main factors affecting their distribution. The findings reveal that the spatial distribution of SICH in the GBA is highly concentrated, with obvious aggregation characteristics. The overall characteristics are “dense in the west, sparse in the east”, forming the distribution pattern of “two cores, three belts”. The “two cores” refers to the formation of a large-scale high-density agglomeration area with southwestern Guangzhou and northeastern Foshan as the core, and another small-scale high-density agglomeration area with southern Hong Kong as the core and expanding from south to north. The “three belts” refers to the formation of three areas of agglomeration density in central Guangzhou-northeastern Jiangmen, western Guangzhou-eastern Zhuhai and Dongguan-Hong Kong. The spatial distribution of the four different types of SICH varies considerably, with significant variations in density. The spatial distribution pattern of SICH in the GBA is mainly influenced by socioeconomic and history and culture, with population, social organization, urbanization level, economic development level, and policy support being the dominant factors, and the influence of physical geography being less strong. The role of influencing factors after interaction is generally strengthened, among which the interaction between urbanization level and social organization is the most obvious. The distribution pattern of SICH in the GBA is subject to the synergy effect of multiple factors. From the perspective of synergy theory, the internal mechanism of its spatial distribution is explained from the logic framework of “synergistic dynamic—synergistic structure—synergistic relationship”. Finally, the study proposes suggestions for the synergistic development of SICH in the GBA in terms of promoting cross-regional cooperation, securing government support, enhancing resource allocation and digital dissemination.

Over the years, the emergence of novel H5 and H7 highly pathogenic avian influenza viruses (HPAI) has been taking place through two main mechanisms: first, the conversion of a low pathogenic into a highly pathogenic virus, and second, the reassortment between different genetic segments of low and highly pathogenic viruses already in circulation. We investigated and summarized the literature on emerging HPAI H5 and H7 viruses with the aim of building a spatio-temporal database of all these recorded conversions and reassortments events. We subsequently mapped the spatio-temporal distribution of known emergence events, as well as the species and production systems that they were associated with, the aim being to establish their main characteristics. From 1959 onwards, we identified a total of 39 independent H7 and H5 LPAI to HPAI conversion events. All but two of these events were reported in commercial poultry production systems, and a majority of these events took place in high-income countries. In contrast, a total of 127 reassortments have been reported from 1983 to 2015, which predominantly took place in countries with poultry production systems transitioning from backyard to intensive production systems. Those systems are characterized by several co-circulating viruses, multiple host species, regular contact points in live bird markets, limited biosecurity within value chains, and frequent vaccination campaigns that impose selection pressures for emergence of novel reassortants. We conclude that novel HPAI emergences by these two mechanisms occur in different ecological niches, with different viral, environmental and host associated factors, which has implications in early detection and management and mitigation of the risk of emergence of novel HPAI viruses.

Exploring the green transition of cultivated land use from the perspective of green utilization efficiency evaluation has become an important content of deepening the study of cultivated land use transition, which is of great significance to promote food security and ecological civilization construction. At present, there are few studies on the green utilization efficiency of cultivated land (GUECL), which covers the comprehensive benefits of economy, ecology and society, combined with the requirements of ecological civilization and green development. Taking 65 cities (regions and autonomous prefectures) of the Yellow River Basin as the basic evaluation unit, the GUECL of the Yellow River Basin is evaluated with a Super-SBM model. In general, the GUECL of the Yellow River Basin was not high at four time points of 2000, 2006, 2012 and 2018, which presents a trend of “rising first and then falling”. Analyzing its temporal and spatial evolution pattern, the GUECL in the upper, middle and lower reaches presented an order of the upper reaches area > the lower reaches area > the middle reaches area; and the spatial variation trend showed a decrease from west to east, and a U-shaped change in the south-north direction. Using spatial correlation analysis, except for the year 2000, the GUECL in the Yellow River Basin presents a general distribution characteristic of spatial agglomeration, which is positively correlated in 2006, 2012 and 2018. The change of spatio-temporal pattern is the result of internal and external factors. The former mainly displays in the main characteristics of farmers, family characteristics and farmers’ cognition, while the latter is reflected in natural, social and policy factors.

Land use conflict, as the spatial manifestation of conflicting human-land relationship, has a profound impact on sustainable use of regional land resources. Taking the Yellow River Basin (YRB) as an example, a land use conflict assessment model was constructed based on landscape pattern indices. The dynamic patterns and driving factors of land use conflict in the YRB and the corresponding driving factors were then assessed from 2000 to 2020 based on spatial autocorrelation analysis and the geodetector method. Significant spatial and temporal differences in land use conflict were observed in the YRB from 2000 to 2020. During this period, the area of stable controllable decreased by 3465 km 2 , whereas the areas of strong and extreme conflict increased by 34,964 and 13,057 km 2 , respectively. The expansion of areas with extreme and strong conflict mostly occurred in regions with high urbanization and human activity, including northern Shaanxi, Hetao Plain, and the Yellow River Delta. The distribution of land use conflict in the YRB from 2000 to 2020 was characterized by significant spatial agglomeration; high-value cluster conflict mainly extended from the midstream area to the upstream area, whereas low-value clusters tended to be concentrated in the upstream area of the Qinghai and Qilian Mountains. The spatial and temporal differentiation in land use conflict from 2000 to 2020 was influenced by factors related to the natural environment, geographic location, social economy, and regional policy in the YRB. The effects of elevation, distance to the nearest major river, population, economic density, and per capita disposable income of residents increased continuously during the study period, whereas the influences of mean annual precipitation and ecological retreat weakened. Analysis of the interactions between driving factors showed significant dual-factor and non-liner enhancement effects on the spatial and temporal differentiation in land use conflict. The findings provide a scientific reference for the comprehensive management of national land and ecological construction in the YRB. Graphical Abstract

The unbalanced development of production-living-ecological land (PLEL) on the northern slope of the Tianshan Mountains has led to a series of environmental and ecological problems. Clarifying the evolution of spatial and temporal patterns and driving mechanisms of the PLEL is highly important for promoting the optimization of land use functions and sustainable development in this region. Previous research has focused primarily on the area or probability of conversion between different types of PLEL, neglecting the overall structural characteristics of the PLEL system. It is difficult to quantify the connectivity and importance of each PLEL type within the entire PLEL system, making it challenging to identify key PLEL types. Furthermore, quantitative characterization of the PLEL system stability is lacking. Accordingly, in this paper, PLEL conversion networks were constructed on the basis of complex network theory, and the dynamic evolution of the PLEL was analyzed from a systemic and holistic perspective. Network metrics (weighted degree, integrated node centrality, and average path length) were calculated to identify key types of PLEL, analyze the main conversion processes of PLEL, and quantify the stability of the PLEL system. The results indicated that: (1) In the PLEL system, ecological land occupied a dominant position but gradually declined between 2000 and 2023. (2) The grassland ecological land, agricultural production land, and ranching production land all had high integrated node centrality and were identified as key types in the PLEL conversion network from 2000 to 2023. (3) The conversion of grassland ecological land, ecological accommodation land, and ranching production land into agricultural production land were the main process of PLEL conversion, with conversion ratios of 53%, 28%, and 16%, respectively. (4) The average path length of the PLEL conversion network from 2000 to 2023 was 1.153, indicating that the overall stability of the PLEL system was poor and that the conversion between PLEL types was easy. (5) The PLEL evolution was the combined result of natural, economic, and social factors. This study demonstrated that complex network models can effectively identify key regulatory land types within the PLEL system. Furthermore, the system’s high instability serves as a warning that the current PLEL development model is unsustainable. This insight provides a crucial scientific basis for precise spatial management and ecological security safeguards on the northern slope of the Tianshan Mountains.

Exploring the interplay between the spatial and temporal distribution of geological hazards and the complex hazard-prone environment provides valuable insights for effective management of geological hazards. We analyzed the spatial and temporal distribution characteristics of historical geological hazards in Hunan Province from 2015 to 2022 using standard deviation ellipse, mean nearest neighbor, and kernel density estimation. We also employed three machine learning models to evaluate the susceptibility of geological hazards. Our research reveals that the frequency trends of landslide, debris flow, and collapse over time exhibit highly similar characteristics, and their high-density areas in spatial distribution significantly overlap. Spatial correlation analysis and kernel density estimation show that geological hazards tend to aggregate in certain areas. Central Hunan and its surrounding regions are high-density areas for geological hazards, with the most severe surface collapses occurring in the Loudi area. Geological hazards are more likely to occur at the intersection of various administrative regions, and landslides, in particular, manifest as multi-point distributions, forming a belt around cities—especially in the Hengyang area, surrounded by ridges and mountains. The locus of gravity shift for geological hazards is complex, yet the distance is small, and it primarily concentrates in and around Loudi. Lithology is the most crucial factor affecting geological hazards, followed by elevation and the topographic relief index. The extreme gradient boosting model achieved an AUC value of 0.786, outperforming the random forest and support vector machine models. The susceptibility assessment aligns closely with the kernel density estimation results. This study provides a solid foundation for understanding the spatiotemporal evolution and susceptibility of geological hazards on a local scale, thereby aiding in hazard risk prevention and control.

【Background and objective】 Evapotranspiration (ET) is an important component in the hydrological cycle and is affected by many biotic and abiotic factors. Understanding its spatiotemporal variation in a region is hence central to help improve its water management. The objective of this paper is to analyse the spatiotemporal variation of ET across the Manas River Basin in Xinjiang of China. 【Method】 The analysis was based on data measured between 2000 and 2018. ET were obtained from the 500 m MOD16 ET product and the meteorological data measured from the basin; we considered five spatial resolutions and the time scale in the analysis was seasonal. From spatiotemporal distribution of ET in the region, we calculated its response to land use types, temperature and precipitation, using the means of mosaic, resample, grid calculation, linear regression and trend analyses. 【Result】 The annual average ET in the basin varied from 16.08 to 598.77 mm/a. Seasonally, the average ET in spring, summer, autumn and winter was 55.29 mm, 102.02 mm, 50.98 mm and 28.45 mm, respectively. The impact of land usage on ET can be ranked in the order of woodland> water body> cultivated land> spare land> construction land> grassland. For all land use types, ET peaked in summer, followed by spring, with winter being the least. The spatiotemporal variations in both ET and precipitation followed the same trend, and the correlation coefficient between them was 0.67. There was a weak but positive correlation between ET and air temperature. 【Conclusion】 Spatial variation of ET across the Manas River basin was significant. Temporally, ET was the greatest in summer and the least in winter; spatially, ET was high in the middle, and low in the south and north of the region. Along the river, ET was high in the middle reaches and low in the upper reaches.