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As a fundamental element of global carbon storage, the storage carbon in terrestrial ecosystem is significant for climate change mitigation. Land use/cover change (LUCC) is a main impact element of ecosystems' carbon storage. Evaluating the relation between land use change and carbon storage is vital for lowering global carbon emissions. Taking Hainan Island as an example, this paper employs the InVEST as well as the CA-Markov models to assess and predict how different land use affects carbon storage in various situations from 2000 to 2020 and from 2030 to 2050 on Hainan Island. The influence factors, together with driving mechanisms of carbon storage spatial distribution are quantitatively analyzed as well in this paper. The results demonstrate that, from 2000 to 2020, Hainan Island's net increase in built land was 605.49 km2, representing a growth rate of 77.05%. Over the last 20 years, Hainan Island's carbon storage and density have decreased by 5.90 Tg and 1.75 Mg/hm2, respectively. The sharp rise in built land mainly makes the carbon storage decline. From 2030 to 2050, land use changes on Hainan Island are expected to result in differing degrees of carbon storage loss in various scenarios. In 2050, Hainan Island's carbon storage will decline by 17.36 Tg in the Natural Development Scenario (NDS), 13.61 Tg in the Farmland Protection Scenario (FPS), and 8.06 Tg in the Ecological Protection Scenario (EPS) compared to 2020. The EPS can efficiently maintain carbon sequestration capability, but it cannot effectively prevent cropland area loss. Regarding the carbon storage's spatial distribution, Hainan Island generally exhibits a pattern of high carbon storages in the low and middle carbon storages in the surrounding areas. Areas with high value are primarily located in Hainan Island's central and southern mountainous areas, whereas areas with low value are primarily located in surrounding areas with lower elevations, primarily encompassing built land and cropland. Geographic detection presented the spatial differentiation of carbon storage in Hainan Island is mainly influenced by factors like slope, land use intensity, and DEM, as well as its interaction with other factors is significantly strengthened (p < 0.05). Under the strategic framework of the "carbon peaking and carbon neutrality" goal and the national ecological civilization pilot zone, it is imperative to carefully consider scenarios for ecological protection and farmland protection, adopt ecological regulation models with spatial differentiation, and implement land use policies to improve ecosystem stability, which will contribute to carbon storage loss reduction and ensure food and ecological security. [ABSTRACT FROM AUTHOR]

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China is advocating the ecological civilization for a sustainable society and resource–economic–environmental system due to its environmental and climate problems. As a special resource–economic–environmental system, island systems are facing severe challenges due to the vulnerable coordination ability between ecological environment and economic development. To measure the sustainable performance of island systems more directly and specifically, this paper extends the concept of ecological efficiency to inclusive ecological efficiency. For the first time, we analyze the inclusive eco-efficiency of Hainan Island, the second largest island in China, from 2008 to 2017. Due to the large technological heterogeneity among the diverse industries, this paper combines inclusive eco-efficiency with meta-frontier data envelopment analysis (DEA). And we propose a revised meta-frontier slack-based measure (SBM) model and meta-frontier non-radial directional distance function (NRDDF) model, which makes the technology gap rate (TGR) no larger than 1. The empirical results show that the average inclusive total factor energy efficiency (ITFEE) of the tertiary industry under the group-frontier is the largest while the average ITFEE of the primary industry is the highest under the meta-frontier. Moreover, the technology gap rate of the primary industry is the largest. Policy implementations are presented based on the empirical results. [ABSTRACT FROM AUTHOR]

Tourism resources are the basic materials of tourism development, and they also provide the support for regional tourism spatial competition. The development of tourism depends on the degree to which tourism resources are utilized, and it is of great guiding significance for their development and utilization to study their spatial structure. Based on a large sample of data on tourism resources, and starting from the characteristics of multi-type, multi-level and multi-combination, this paper puts forward a framework and method for analyzing the spatial structure of tourism resources. Taking Hainan Island as an example, this paper describes the spatial structure of tourism resources in Hainan Island by using the method of point pattern analysis, identifies the tourism resource development zones, and puts forward some suggestions for the development of tourism resources. The results are as follows: (1) The characteristic scale of the spatial structure of tourism resources in Hainan Island is 30.5 km, and there are significant differences in the distributions of all kinds of tourism resources. (2) Through the spatial structure map of tourism resources, the tourism resource development zones are identified, including three tourist central city levels, "one horizontal and three vertical" tourist belts and four tourist combination areas. (3) By combing the distribution of tourism resources and the development zones in Hainan Island, the cross-border characteristics of the tourism resources and development zones are obvious. In order to give full play to the spatial combination and superposition effect of tourism resources, a change from a single isolated development mode to the overall combined development between regions is suggested. On the provincial scale, it is relatively accurate to describe the spatial structure of tourism resources for point data with a large sample size. However, the method of point pattern analysis can not only accurately describe the spatial structure of tourism resources, but it can also provide reference for other types of regional spatial analyses. The research results provide a scientific basis for the spatial planning of regional tourism resources and have practical significance for the development of regional tourism. [ABSTRACT FROM AUTHOR]

Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hainan Island is a key part of the eastern Tethyan region and contains detailed geological information that can enhance our understanding of the tectonic evolution of this region since the late Palaeozoic. In this paper, we report geochronological, geochemical, and Sr–Nd isotopic data for granitoids from Baomei and Chahe in the northern part of Hainan Island. Three new zircon U–Pb ages of 243.3 ± 1.7 Ma, 237.1 ± 5.1 Ma, and 257.0 ± 4.0 Ma were obtained for these granitoids. The late Permian Chahe granite (257 Ma) is weakly peraluminous to peraluminous, and has rare earth element patterns and Ga/Al and FeOT/MgO ratios typical of A‐type granites formed in an extensional tectonic setting. The Middle Triassic Baomei granitoids (243–237 Ma) are weakly peraluminous, and exhibit a negative correlation between P2O5 and SiO2, which is typical of I‐type granites. All the granitoids have EM II‐type‐enriched mantle Sr–Nd isotopic compositions, which indicate that they were derived from a mantle source that had experienced enrichment and metasomatism. Hainan Island was in an extensional tectonic setting from the late Permian to Middle Triassic when widespread A‐ and I‐type granites were generated. We speculate that Hainan Island was mainly affected by the Tethyan tectonic domain during the Permian–Triassic, which involved closure of the Palaeo‐Tethys Ocean, collision of the Indochina and South China blocks, and subsequent post‐collisional extension. [ABSTRACT FROM AUTHOR]

Copyright of New Architecture is the property of New Architecture Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

On Hainan, it is commonly believed that people who identify themselves as Han employ ritual masters (commonly known as daogong 道公) who use texts, while those who view themselves as Li employ the service of geba (no applicable Chinese characters) who do not. This paper argues that the use of Chinese ritual texts implies that the specialist possessing them belongs to a larger religious movement, while those specialists without texts emphasize their own powers as well as those of the masters who instructed them. At the same time, however, my historical and field research indicates that the use of texts has been spreading throughout the Five Finger Mountain region throughout the nineteenth and twentieth centuries, thereby prompting significant changes towards hybrid rituals and the denial of any Li connection. While the ethnic differentiation (minzu shibie 民族識別) campaigns beginning in the 1950s have promoted a sense of ethnic identity, the growing use of written texts indicates that Li ritual practices have been converging with those of the Han. [ABSTRACT FROM AUTHOR]

Hainan Island in southern China is situated within the Indo-Burma biodiversity hotspot, and has attracted the attention of evolutionary biologists, geologists, and biogeographers. However, the palaeogeography of Hainan Island and its relationship with mainland China remains contested. In this paper, we report RAD-seq data for Engelhardia roxburghiana populations from Hainan Island and adjacent mainland areas to identify genetic diversity, structure, divergence time, and demographic dynamics over geologic time. Findings were assessed using climate model data to constrain suitable distribution areas. Results indicate that E. roxburghiana dispersed from the Chinese mainland to Hainan Island via a hypothetical land bridge during the late Eocene so that the drift of Hainan Island was impossible. We cast doubt on the hypothesis that Hainan Island was connected to Vietnam and Guangxi at this time. We emphasize that higher genetic diversity in the Yunnan-Guizhou Plateau and Chiang-nan regions is the result of mixed populations or the existence of refugia, and lower genetic diversity in the Indochina Peninsula is due to a historical bottleneck. From the late Eocene to Oligocene, the arid belt that dominated East Asia retreated, facilitating the expansion of E. roxburghiana from the Indochina Peninsula to southern China. The main diversification of E. roxburghiana occurred in the Miocene following the strengthening precipitation within the East Asian Summer Monsoon. Climatic oscillations during the Quaternary led to the contraction of E. roxburghiana in the Indochina Peninsula, with expansion after Last Glacial Period (LGP; 119 to 11.7 ka). Southern China has served as a refugium and continues to do so in the future. In summary, our study elucidates the evolutionary trajectory of E. roxburghiana through large-scale sampling, providing insights into the palaeogeography of Hainan Island and itsbiogeographic relationships with adjacent mainlands. • A land bridge facilitated the spread of Engelhardia roxburghiana from Chiang-nan to Hainan Island in the late Eocene. • Engelhardia roxburghiana 's evolution follows Asian climate shifts, spreading north as arid zones retreated. • The diversification of Engelhardia roxburghiana occurred concurrently with intensified EASM precipitation during the Miocene. • Southern China was the refugium during the Quaternary glaciations and continues to do so in the future. [ABSTRACT FROM AUTHOR]

The sustainable protective efficiency of Casuarina equisetifolia coastal protection forest（CCPF） in Hainan Island has been seriously affected as C. equisetifolia itself can not regenerate naturally. In this paper, Haikou CCPF was taken as the test area of the natural habitat, and a total of 36 treatment combinations were designed by using 5-factor 2-level factor test method to explore the impact factors and barrier factors of C. equisetifolia seed germination and seedling survival. The results were as follows:（1） The treatment combination with the highest seed germination rate of C. equisetifolia was canopy gap-not watering-sandy soil-water retention-covering soil（GJ0 SBM）, with 37.33% of the germination rate, which was significantly higher than those of other treatment combinations（P<0.05）. The treatment combination with the highest average plant height was canopy gap-watering-red soil-no water retention-not covering soil（GJRB0 M0）, with the plant height of 6.43 cm in 53 d, which was significantly higher than those of other treatment combinations（P<0.05）. The treatment combination with the highest survival rate was canopy gap-watering-sandy soil-water retention-covering soil（GJSBM）, with 79.00% of the survival rate for 73 d, which was significantly higher than those of other treatment combinations（P<0.05）.（2） Stand light conditions and covering soil patterns were the impact factors for seed germination rate and germination potential of C. equisetifolia, while water retention patterns had significant effects on seed germination speed.（3） Stand light conditions were the impact factors for C. equisetifolia seedling plant height.（4） Watering treatment was the main factor affecting the survival rate of C. equisetifolia seedlings. In summary, the barrier mechanism of C. equisetifolia natural regeneration unable to survive in Hainan dry season is not for the seed germination, but for the lack of necessary water, resulting in the failure of C. equisetifolia itself natural regeneration. [ABSTRACT FROM AUTHOR]

The establishment of multi-planning integration (MPI) and an orderly spatial planning system has been identified as one of the most important issues in China. Since 2014, 28 counties and cities have been selected as typical examples in China to launch MPI pilots. The Hainan Island MPI pilot is the only one that contains coastal waters, which makes it particularly valuable to coastal zone management research. In this paper, we present a qualitative study of the Hainan Island MPI pilot to gain insights into the methodological approaches of the MPI framework that have led to the integration of dozens of diverse planning initiatives in this coastal area, and summarize the significance of advancing integrated coastal zone management. The findings were drawn from comparisons of previous coastal spatial management scenarios, interviews of MPI-related government officials, and an overlay analysis of MPI achievements conducted using ArcGIS. These findings revealed that, as it was conducted in a coastal province, the Hainan Island MPI pilot considered the substantial relationship between the sea and the land, and the MPI advanced the coastal management through the use of several reform measures, including setting up the framework of an overall planning system to unify previous planning conflicts, forming a blueprint to optimize the coastal land and sea conservation and development, establishing a new provincial spatial management agency to instruct all spatial management, strengthening the legislation to guarantee the legal status of MPI, establishing a planning inspection mechanism to contain illegal land and sea use, establishing a comprehensive information platform to make spatial management convenient, and promoting the reform of an administrative approval system to accelerate the examination of coastal activity. Moreover, this study emphasizes the need for an integrated land and marine spatial planning framework to mitigate the conflicts of sectoral management to achieve more efficient coastal management, and MPI could be one option for the same; however, a more integrated planning method should be explored to further reflect the integrity of the coastal resources and environment. [ABSTRACT FROM AUTHOR]

As escalating environmental pressures threaten the world's beaches, understanding the driving factors influencing their geomorphological changes is of critical global importance. This study focuses on the morphological changes of Sigeng beach adjacent to Changhua River Mouth in Hainan Island, China through decadal monitoring of shoreline and profile topography and tries to illuminate the natural and anthropogenic factors that drove geomorphological changes. The results showed that Sigeng beach undergone significant changes between 2008 and 2024, with notable accretion at the northernmost and southernmost and general erosion at other sections. The shoreline change rates ranged between -18.4 m/yr and 13.0 m/yr, with the average rate of -1.9 m/yr, indicating overall erosion. The net longshore sediment transport (LST) rates along Sigeng beach was estimated through the combination of the cross-shore (profile) and longshore (shoreline) changes. The overall direction of net LST along the beach were southward, except for the northern section where the direction was northward due to the diffraction of NE waves by the long sand spit at the northernmost. The net LST rates at each profile varied from 0.8×104 m³/yr to 3.5×104 m³/yr. The main factors controlling Sigeng beach evolution, including seasonal wave action and reduction in fluvial sediment load, followed by sand spit and coastal structures, typhoon events, aeolian transport, and sea level rise, were discussed. Subsequently, adaptive protection measures, including beach nourishment, accompanied with groin system or multiple detached breakwaters were proposed to combat with beach erosion. The analysis presented in this study is helpful to understand the morphodynamics and to predict the future change of beaches. [ABSTRACT FROM AUTHOR]

A coastline is the boundary zone between land and sea, an active zone of human social production activities and an area where the ecology is fragile and easy to change. The traditional method to analyze temporal and spatial changes in the coastline is to extract the coastline through remote sensing, LiDAR, and field sampling and analyze the temporal and spatial changes with statistical data. The coastline extracted by these methods has high spatial and temporal resolution, but it requires remote sensing images and data obtained by other sensors, so it is impossible to extract coastlines from before the emergence of remote sensing technology. This paper improves the coastline generation algorithm. Firstly, a triangulated irregular network is used to generate the preliminary rough coastline, and then, each line segment is optimized with Python language according to the influence range of the place names to further approach the real coastline. The accuracy of the coastline extracted by this method can reach 80% within 500 m, which is of great significance in the mapping and analysis of small- and medium-scale coastlines. This paper analyzes the changes in the coastline of Hainan Island before the founding of China (pre-founding) and in modern times and analyzes the impact of coastal development on coastline change. Through the analysis, it is found that, from before the founding of the People's Republic of China to the present, the natural coastline of Hainan Island has become shorter, the artificial coastline has become longer, and the coastline generally presents a trend of advancing toward the ocean. This method realizes coastline construction under the condition of missing remote sensing images and puts forward a new way to study historical coastline changes. [ABSTRACT FROM AUTHOR]

As a Free Trade Port in China, the protection of ecological environment and highquality tourism development on Hainan Island have become a national strategy. Exploring the coupling relationship of the two subsystems holds great practical significance for promoting the island's international demonstration area and high-quality development. Based on the characteristics of international islands, a comprehensive index system is established to explore the coupling coordination evolutionary process and interactive stress relationship of tourism development and the ecological environment in Hainan Island from 2005 to 2020. The results show: (1) From 2005 to 2019, the comprehensive evaluation index of the two subsystems of Hainan Island generally showed a continuous growth trend. (2) From 2005 to 2019, the coupling degree of the two subsystems of Hainan Island strengthened continuously, the coupling coordination degree increased steadily from a moderate imbalance to good coordination, and tourism development and the ecological environment entered a stage of parallel and benign interactive development. (3) In 2020, affected by COVID-19, the tourism development indicators declined rapidly, while the ecological environment still maintained a rising trend. (4) Based on the inverted U-shaped curve model, when the tourism development index reaches 0.7269, the ecological environment quality reaches the maximum value of 0.7956, which is the best state between the two subsystems. The ecological environment and tourism development of Hainan Island are generally in a benign interaction, but there are signs of interactive stress starting in 2017. In the future, the pressure on the ecological environment of Hainan Island will increase. [ABSTRACT FROM AUTHOR]

Previous research has primarily focused on soil erosion issues in arid and semi-arid regions, with a limited understanding of soil erosion mechanisms in tropical areas. Additionally, there is a lack of a holistic perspective to determine the spatial attribution of soil erosion. The conversion of tropical rainforests into economically driven plantations, like rubber and pulpwood, has resulted in distinct soil erosion characteristics in specific regions. To enhance our knowledge of soil erosion patterns and mechanisms in tropical regions, it is necessary to examine soil erosion in the three major watersheds of Hainan Island from 1991 to 2021, which encompass significant geographical features such as tropical island water sources and tropical rainforest national parks. The study employed the China Soil Loss Equation (CSLE) model, slope trend analysis, Pearson correlation analysis, land-use transfer matrix, and spatial attribution analysis to examine soil erosion under different scenarios. The research results indicate that scenarios driven by the combination of natural and human factors have the greatest impact on soil erosion changes in the entire study area. Co-driven increases affected 53.56% of the area, while co-driven decreases affected 21.74%. The 31-year soil erosion showed an overall increasing trend. Human factors were identified as the primary drivers of increased soil erosion in the Nandu River basin, while a combination of climate and anthropogenic factors influenced the decrease in soil erosion. In the Changhua River basin, climate and human activities contributed to the soil erosion increase, while human activities primarily caused the decrease in soil erosion. In the Wanquan River basin, climate intensified soil erosion, whereas human activities mitigated it. This study underscores the significant combined impact of human activities and natural factors on soil erosion in tropical regions. It emphasizes the importance of considering human-induced factors when implementing soil erosion control measures in tropical regions. [ABSTRACT FROM AUTHOR]

his study assesses the performance of three high-resolution regional numerical models in predicting hourly rainfall over Hainan Island from April to October for the years from 2020 to 2022. The rainfall amount, frequency, intensity, duration, and diurnal cycle are examined through zoning evaluation. The results show that the China Meteorological Administration Guangdong Rapid Update Assimilation Numerical Forecast System (CMA-GD) tends to forecast a higher occurrence of light precipitation. It underestimates the late afternoon precipitation and the occurrence of shortduration events. The China Meteorological Administration Shanghai Numerical Forecast Model System (CMA-SH9) reproduces excessive precipitation at a higher frequency and intensity throughout the island. It overestimates rainfall during the late afternoon and midnight periods. The simulated most frequent peak times of rainfall in CMA-SH9 are 0–1 hour deviations from the observed data. The China Meteorological Administration Mesoscale Weather Numerical Forecasting System (CMA-MESO) displays a similar pattern to rainfall observations but fails to replicate reasonable structure and diurnal variation of frequency-intensity. It underestimates the occurrence of long-duration events and overestimates related rainfall amounts from midnight to early morning. Notably, significant discrepancies are observed in the predictions of the three models for areas with complex terrain, such as the central, southeastern, and southwestern regions of Hainan Island. [ABSTRACT FROM AUTHOR]

Using the high-resolution numerical weather research and forecasting (WRF) model, study the squall line process that occurred on Hainan Island on 22 April 2020. The findings indicate that high terrain blocks the swift accumulation of water vapor carried by the sea breeze and aids in preserving the accumulated water vapor. According to the sensitivity experiment, terrain height has minimal impact on the macroscopic effects of mesoscale weather processes. However, it does influence where the sea breeze converges. During this process, the ocean-land thermal contrast not only takes the main responsibility for the sea breeze but also leads to uplift motion, which affects the formation, intensity, and duration of the squall line. Additionally, the unstable conditions suggest that a thermal and dynamic environment promote the scale of this squall line. Utilizing the Rotunno–Klemp–Weisman theory (RKW), this study analyzes the effects of the cold pool and vertical wind shear. The analysis reveals that significant vertical wind shear at lower levels and the ground-cold pool contribute to the sustenance and growth of the squall line system. This squall line process has had the greatest impact on the Haikou area due to the strong low-level vertical wind shear and prolonged interaction with the cold pool. When the interaction between the cold pool and the vertical wind shear weakens, the squall dissipates. [ABSTRACT FROM AUTHOR]

The traditional research on tourism product development can be roughly divided into two types: one is based on resources school, such as regional economics, theory of developing islands, the other is based on marketing school represented by pubic marketing of tourism descrinarion, tourist behavior. As tourism product includes a number of physcal products and intangible services, the same kind of tourism products always brings different values and psychologcal feelings to different tourists. Exìsiing resea-ches cannot combine tourist psychologcal preference and resources well. To solve this problem, thìs paper tries to introduce "meansend chain" approach of markeiing to study the touist value of Hainan Island. It analyzes the contents of tounsm product attrib utes, tounsm consumption consequences and touhst values of Hainan Island and vehlies the signiricant positive correlation among these three elements by applying Pearson co-relation coefficient method. The this paper constructed a Hierarchical Value Map for ths touhsts of Hainan Island and dìscusses the meanend chain path to which touhsts pay most attention by constructing an incidence matrix among atthbutes, consequences and values. On the basss of the lindings mentioned above, this paper puts forward some pro-posals to develop touhst products in Hainan tounsm, including to enhance the construc-tion of the touhsm brand image of Hainan Island and to reconduct market segmentation of touhsts. [ABSTRACT FROM AUTHOR]

Modern palms are diverse and widespread in the tropics and subtropics, especially the tropical rainforests. However, most fossil palm records have been reported from regions of relatively higher latitude. In this paper seven species of coryphoid palm from the Eocene Changchang Basin of Hainan Island of South China are reported. These are Sabalites asymmetricus sp. nov., S. robustus sp. nov., S. tenufolius sp. nov., S. szei Guo, S. changchagnensis Guo, Livistona sp., and Amesoneuron sp. According to leaf morphological characteristics, they can be classified as members of the subfamily Coryphoideae. In extant flora of Hainan Island, only three species of Livistona have costapalmate leaves. These palm fossils indicate that, during the Eocene, flora in Hainan Island included a diversity of coryphoid palms, which have some bearings on the reconstruction of the palaeoclimate of South China. [ABSTRACT FROM AUTHOR]

Will tourism development bring about inflation? The paper examines the causal relationship between tourism industry and inflation in Hainan Island. The cointegration test indicates that there is a long-term relationship of equilibrium between tourism industry and inflation in Hainan Island. A Granger causality also supports that tourism industry in Hainan will bring about inflation in one direction. In addition , the empirical evidence of impulse response function clearly shows that tourism growth in Hainan can produce a positive push to inflation. In the end, the paper holds the view that the main reason of pushing CPI growth is the tied development of tourism and real estate and the surge in short-term residents with their second homes in Hainan Island. [ABSTRACT FROM AUTHOR]

The genus Eriovixia Archer, 1951 is a small tropical genus and exhibits a wide geographical distribution from Southeast Asia to Africa. In this paper, the genus Eriovixia is revised in Hainan Island, China, and three new species, E. nigrimaculata sp. nov., E. huwena sp. nov. and E. jianfengensis sp. nov., are described. Based on the type species description and three species figures, we think Tukaraneus Barrion & Litsinger, 1995 is a junior synonym of Eriovixia Archer, 1951. Accordingly, three species, Tukaraneus mahabaeus Barrion & Litsinger, 1995, Tukaraneus palawanensis Barrion & Litsinger, 1995 and Tukaraneus patulisus Barrion & Litsinger, 1995, are transferred from Tukaraneus to Eriovixia. E. excelsa (Simon, 1889), E. pseudocentrodes (Bosenberg & Strand, 1906) and E. sakiedaorum Tanikawa, 1999 are recorded for the first time for Hainan Island's fauna. A key to the genus Eriovixia is presented excepting three species distributed in Africa. Biogeographic analyses show that Southeast Asia is a centre of distribution, diversification and speciation of the genus Eriovixia, and Hainan Island's fauna posesses high species richness and endemism. [ABSTRACT FROM AUTHOR]

Seed dynamics is an important part of stand dynamics in forest ecosystems. In this paper, 26 gaps were randomly selected to study the influence of gaps on the spatial and temporal patterns of seed rains in a tropical montane rainforest of Hainan Island, South China. Three zones for each gap, including outside gap zone (Non-gap), transitional gap zone (EG-CG), and central gap zone (CG), were designed, and four seed traps (each 1m × 1m in size) were placed in each zone. Seed rains were collected by these traps every 10 days from June 2001 to May 2002. Seed rain varied greatly with season and generally exhibited a pattern of unimodal change during the study period: seed abundance and species richness were both greater in the wet season than in the dry season. Gaps significantly influenced the temporal patterns of both species richness and density of seed rains. Gaps had no significant influences on the spatial distribution patterns of seed rain species richness, but significantly affected the spatial distribution pattern of seed rain densities. Among the three different zones of gaps, the outside gap zone generally received more seeds inputs than the two other gap zones. [ABSTRACT FROM AUTHOR]

The impacts of economic forest on global environmental change(GEC) are one of the hot issues in environmental study. Based on the 3-year observation data and 40-year climate data, GEC and analysis of the hydrological dynamic characteristics of rubber plantations and estimate of the water balance in the rubber plantations in Hainana Island were made. The results showed that the rainfall intercepted by the canopy of the plantations accounted for 11.45% of the annual rainfall, the total runoff for 23.71%, the total evaporation and transpiration for 63.24% , the soil moisture storage for 1.6% . Analysis of the 40-year rainfall data in the 19 counties of Hainan Island during 1951--1990 showed that the large-scale substitution of the the natural vegetation with the rubber plantations had no significant effect on the local rainfall in Hainan Island. The main reasons are (1) 80% of the rainfall in Hainnan in brought by typhoons: (2) the proportion of 11.6% rubber plantations in total forest coverage in Hainan is not enough to influence the local ranfall in Hainan Island; and (3) although the rubber plantation is artificial vegetation, it has the similar function to the tropical rain forest. Analysis of the total water resource and total GDP of Hainan in 1997 showed that the economic benefit resulted from the water resource was 1.0 RMB Yuan/m[sup3]. The value of hydrological of the rubber plantation in Hainan was 113.9 million RMB yuan/a when compared with tropical rain forest. The paper reaches conclusion that the hydrological eco-service function of rubber plantation has been enhanced after transformed from natural vegetation, which includes the natural service and powerful social service. [ABSTRACT FROM AUTHOR]

Typhoon is one of the major natural disasters impacting Hainan Island, and it is often accompanied by other disaster phenomena such as storm surges and high wind waves, which in turn pose a great threat to human lives and assets. In this paper, the Holland typhoon model and the Miyazaki Masae wind field model are adopted to simulate the typhoon-induced wind field for Hainan Island oceans. The hybrid wind field is established by the parametric wind field and the ERA5 reanalysis wind field. The ADCIRC+SWAN coupled model is used to simulate the typhoon wind and wave interactions, and the results reveal that the hybrid wind field model performed well compared to the measured values. Finally, based on the typhoon best-track archive from China Meteorological Administration (CMA), the risks in ocean around Hainan Island are categorized. The hybrid wind field and the ADCIRC+SWAN model is used to establish the risk map for typhoon induced wave fields, considering different typhoon tracks and seasons. [ABSTRACT FROM AUTHOR]

Hainan, a well-known center of tropical agricultural production in south China, has received little attention regarding groundwater fluoride contamination. This study investigates the occurrence of fluoride in the western coastal area of Hainan Island and discusses factors affecting groundwater fluoride contamination in various aquifers and areas with different land-use types using hydrochemistry and multivariate statistical analysis. A total of 100 groundwater samples were collected from the western coastal area of Hainan Island. The results show that the groundwater fluoride concentration is as high as 4.18 mg/L and that F−-high (>1 mg/L) groundwater accounts for 9% of total groundwater. The proportion of F−-high fissure water is about two times that of F−-high pore water. Among the different land-use types, the proportion of F−-high groundwater from highest to lowest is as follows: bare land > cultivated land > woodland > construction land > grassland. The main factor affecting fluoride in pore water is the leaching of fluorine/aluminum-containing minerals such as phlogopite and calcite in the vadose zone, which is characterized by the co-enrichment of fluoride and aluminum in pore water. The leading cause of fluoride in fissure water is the leaching of fluorine-containing fertilizers, and continuous irrigation promotes the cation exchange of sodium, strontium, and calcium, which is characterized by the co-enrichment of fluoride with sodium and strontium in fissure water. Consequently, it is advised to minimize the excessive use of fluoride fertilizers and increase groundwater quality monitoring in order to decrease the emergence of F−-high groundwater in the western coastal area of Hainan Island. [ABSTRACT FROM AUTHOR]

Hainan Island located at the southernmost tip of the continental crust of the South China Plate, has high terrestrial heat-flow values, widely-distributed hot springs, and rich geothermal resources. Intensified researches on the origin and potentials of geothermal resources can promote Hainan Island's development into a clean energy island. To determine the geological conditions for the formation of geothermal resources in southern Hainan Island, we collected core samples of granites from the Baocheng batholith in southern Hainan Island and conducted systematic analysis in respect of petrology, geochronology, geochemistry, and petrophysical property. The results of this study are as follows. The Baocheng batholith in the southern Hainan Island has a crystallization age of 98.42 ± 0.56 Ma, making it the product of magmatism in the early stage of the Late Cretaceous. It mainly consists of high-K calc-alkaline granites, which were intruded by intermediate-to-mafic veins. The Baocheng batholith has a high radioactive heat generation rate of 2.712-6.843 mW/m³, with an average of 3.846 mW/m³, a radioactive heat-flow value of 30.768 mW/m² and a heat-flow contribution rate of 38.95%-43.95%. As shown by the results of their thermophysical property analysis, the granites have high thermal conductivity and can serve as highquality geothermal reservoirs. In combination with previous geological and geophysical data, the geothermal model of the Lingshui area was established in this study. The deep structure indicates the presence of high-conductivity and low-resistivity layers in the basement of the Baocheng batholith. It can be inferred thereby that asthenospheric upwelling may occur and that there exist two magma vents at depth in the batholith. Therefore, magmatic heat at depth and granites with high radioactive heat generation rate serve as the main heat sources in the Lingshui area. [ABSTRACT FROM AUTHOR]

This study explored the ecological niche and interspecific relationships among the main fish species in the coastal waters of Hainan Island based on data from fishery stock surveys conducted in the spring and autumn of 2022. The methods of chi-square test, percentage of co-occurrence (PC), association coefficient (AC), cluster analysis, and redundancy analysis were used to analyze the interspecific associations and influence of environmental factors on the ecological niches of fish communities. According to the cluster analysis of niche breadth, 20 main fishes could be divided into broad, medium, and narrow niche species. There were four and eight broad niche species in spring and autumn, respectively. The ranges of niche overlap values were 0.001–0.91 in spring and 0–0.87 in autumn, indicating that the species differed and were similar in their ability to utilize resources, survive in habitats, and prey. According to the variance ratio and statistic value W, the main fishes in spring showed a significant positive association, whereas those in autumn showed a positive association, but not at a significant level, indicating that the main fishes in spring were more closely associated with each other. There were 56 species pairs in the 2 seasons that were significantly associated (χ2 ≥ 3.841). AC and PC tests revealed that the interspecific association was strong and tended to be positive. According to the redundancy analysis, environmental factors such as surface temperature, water depth, and pH significantly affected the main fishes in spring, while environmental factors such as dissolved oxygen, bottom temperature, surface salinity, and pH significantly affected those in autumn. [ABSTRACT FROM AUTHOR]

Based on the Dynamical–Statistical–Analog Ensemble Forecast model for Landfalling Typhoon Precipitation (DSAEF_LTP model), the optimal forecast scheme for the tropical cyclone (TC) accumulated precipitation over Hainan Island, China (DSAEF_LTP_HN) is established. To test the forecasting performance of DSAEF_LTP_HN, its forecasting results are compared with other numerical models. The average threat score (TS) of accumulated precipitation forecast by DSAEF_LTP_HN is compared with other numerical models over independent samples. The results show that for accumulated precipitation ≥ 100 mm, the TS produced by DSAEF_LTP_HN reaches 0.39, ranking first, followed by ECMWF (0.36). For accumulated precipitation ≥ 250 mm, the TS of DSAEF_LTP_HN (0.04) is second only to ECMWF (0.19). Further analysis reveals that the forecasting performance of DSAEF_LTP_HN for TC precipitation is closely related to the TC characteristics. The longer the TC impacts Hainan Island and the heavier the precipitation delivered to Hainan Island, the better the forecasting performance of DSAEF_LTP_HN is. DSAEF_LTP_HN can successfully capture the center of heavy precipitation. However, there is still a phenomenon of false forecasts for some TC heavy precipitation, which requires further improvement of the model in the future. [ABSTRACT FROM AUTHOR]

Mafic-intermediate igneous rocks in the Bangxi-Chenxing tectonic zone of Hainan Island, South China, can be used to constrain the Paleotethyan tectonic evolution in Southeast Asia. This paper presents petrologic, geochronological, elemental and Sr–Nd–Hf–O isotopic data for Carboniferous basalts, Permian andesites and Triassic gabbro-dolerites in this zone. Zircon grains from these rocks have U-Pb ages of ∼330 Ma, ∼257 Ma and ∼240 Ma, respectively. The ∼330 Ma basalts contain 1400 Ma captured zircon grains, and display MORB-like geochemical characteristics with positive ε Nd (t) values of +5.86–+9.85, reflective of a MORB source with the input of a slab-derived component in a continental back-arc basin setting. The ∼257 Ma andesites contain older captured zircon grains, and have arc-like geochemical signature with weakly positive ε Nd (t) values of +0.26–+0.38, zircon ε Hf (t) values of −0.5–+1.4 and δ 18 O values of 6.35–7.16‰, which were derived from a metasomatized mantle wedge modified by the sediment-derived component in a continental arc setting. The ∼240 Ma gabbro-dolerites exhibit enrichment in LILEs, depletion in HFSEs, negative ε Nd (t)-ε Hf (t) values (−8.45 to −1.05 and −5.9 to −2.7, respectively) and crustal-like δ 18 O values (7.26–8.70‰), indicative of a post-collisional environment in response to the asthenosphere upwelling shortly after the closure of the Bangxi-Chenxing back-arc basin. The Carboniferous-Triassic mafic-intermediate igneous rocks thus record the Carboniferous-Permian arc-basin system and its Triassic closure. The Bangxi–Chenxing tectonic zone separated South Hainan from North Hainan and westerly extended to the Song Ma–Ailaoshan suture zone. [ABSTRACT FROM AUTHOR]

In China, Hainan Island is a priority area for turtle conservation because of its biodiversity. Over the years, errors in turtle taxonomy and distribution have been made in the scientific literature, perpetuating into relevant laws and government documents and affecting conservation and management. In the present article, we describe the species of nonmarine turtles on Hainan Island, China, based on literature, museum specimens, and field surveys during the past 27 yrs. Historically, 23 nonmarine turtle species were recorded on Hainan Island. Among them, 9 species should be removed due to errors: 5 species are not naturally distributed on Hainan Island (Manouria impressa, Sacalia bealei, Cuora flavomarginata, Mauremys nigricans, and Mauremys reevesii), 3 are invalid hybrids (Ocadia philippeni, Sacalia pseudocellata, and Cuora serrata), and 1 is a synonym of another species (Mauremys megalocephala is a synonym of M. reevesii). In addition, of the 3 new species recorded from Hainan Island (Sacalia insulensis, Pelodiscus variegatus, and Pelodiscus parviformis), S. insulensis replaces Sacalia quadriocellata, P. variegatus is valid, and P. parviformis is likely an error. Therefore, there should be 12 nonmarine turtle species naturally found on Hainan Island: Platysternon megacephalum, Cuora galbinifrons, Cuora mouhotii, Cuora trifasciata, Geoemyda spengleri, Mauremys mutica, Mauremys sinensis, S. insulensis, Palea steindachneri, Pelochelys cantorii, Pelodiscus sinensis, and P. variegatus. Clarifying the presence and distribution of nonmarine turtle species will provide a reference for future research and practical guidance for conservation management on this turtle-rich island. [ABSTRACT FROM AUTHOR]

The Papilionoideae is one taxonomically complex subfamily with high economic and medicinal potential. The pollen micro-morphology and taxonomic relevance of this subfamily are still poorly known in the island. Therefore, this study aims to provide new palynological information to correctly identify and define species boundaries within the subfamily. The species were collected from different geographical regions of Hainan Island. Both light and scanning electron microscopic techniques were used to observe pollen traits. Additionally, principal component analysis was performed to elucidate the variation among the taxa. A significant variation was found in exine sculpturing i.e. most of the taxa have reticulate type pollen while Desmodium triflorum has a psilate exine pattern. Variations were found on the surface of the reticula that can help to delimit the species from one another. Pollen type was observed as tricolporate and rarely tricolpate. Similarly, the colpus surface membrane morphology may also vary significantly from species to species i.e. scabrate, verrucate, gemmate, rugulate patterns. Besides, the mergo having various sculpturing found in Canavalia rosea, Desmodium triflorum, D. microphyllum Glycine max, Macroptilium atropurpureum, Erythrina crista-galli and Zornia gibbosa should be considered as a potential taxonomic trait for the subfamily. The maximum P/E ratio was found in Zornia gibbosa (2.24). Similarly, the maximum pollen size was found in Alysicarpus vaginalis (34.64 × 33.99 µm). Our study explored the pollen morphological traits and can be helpful to correctly identify the species and define species boundaries within Papilionoideae at various taxonomic levels. This study strengthens and supports the taxonomic position of the subfamily and will provide bases for further phylogenetic and molecular studies of Papilionoideae. Various taxa of the subfamily Papilionoideae were collected from different geographical regions of Hainan Island, South China. Both light and scanning electron microscopic techniques were used to analyze the ultra-sculpturing of the pollen. Most of the taxa have reticulate exine patterns but variations were found in supra-tectal elements and colpus surface membrane morphology. These variations in pollen traits have significant taxonomic potential and will strengthen the taxonomy of Papilionoideae. This study can help to correctly identify and define species boundaries at various taxonomic levels of the Papilionoideae and will solve the taxonomic problem. [ABSTRACT FROM AUTHOR]

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This study uses numerical simulations to investigate the impact of cross-scale interaction between the cold air pool (CAP) and the synoptic systems on autumnal nighttime rain over Hainan Island. The results show that the precipitation formed initially via the convergence of the southerly wind from a mesoscale vortex located around the Beibu Gulf and the sea breeze along the northwest coast of Hainan Island in the afternoon. Subsequently, this precipitation propagated eastward due to the weakening and southward movement of the vortex, which was promoted by the CAP that formed in the lower troposphere within 2 h after rainfall. The CAP weakened the vortex by forming a sub-2-km divergent wind and accelerating upward propagation of the positive potential vorticity. And the CAP promoted the southward movement of the vortex by increasing the sea level pressure on its northeast side and stimulating a cyclonic disturbance on its southeast side, which was also conducive to the southward shift of cold air from the Chinese mainland. When the cold air arrived at Hainan Island at night, it was deepened by the blocking effect of the sub-2-km divergent wind. The superposition of the blocked cold air and the CAP stimulated a strong northerly land breeze, which merged with the southerly wind to reinvigorate rainfall in the eastern coastal area. This paper reveals the mechanism by which the CAP affects the heavy rainfall at night on Hainan Island in autumn under the combined influence of the tropical disturbance-related vortex and the cold air from the north. • The cold air pool (CAP) can strengthen effectively the autumnal nighttime rainfall on Hainan Island. • The CAP strengthens the rainfall by modulating mesoscale synoptic systems. • The CAP promotes the weakening and southward movement of the mesoscale vortex. • The cold air reaching Hainan Island will be strengthened by the blocking effect of the CAP. [ABSTRACT FROM AUTHOR]

The gross primary production (GPP) of the mangrove ecosystem determines the upper limit of the scale of its "blue carbon" sink. Tropical cyclones (TCs) are among the most important extreme events that threaten the subtropical mangrove ecosystem and have a serious impact on mangrove ecosystem GPP. However, there are somewhat insufficient scientific findings on regional-scale mangrove ecosystem GPP responding to large-scale weather events such as TCs. Therefore, we selected the subtropical Hainan Island mangrove ecosystem, where more than two TCs pass through per year, as the research area; selected direct-attack TCs as the research object; and took the mangrove vegetation photosynthesis light-use efficiency model established based on the eddy covariance observation data as the tool to evaluate the loss and recovery of mangrove ecosystem GPP after TCs attacked at a regional scale. We found that the TC impacted the mangrove ecosystem GPP through the photosynthetic area and rate, and the recovery of the rate occurred prior to the recovery of the area; the loss of mangrove ecosystem GPP is inversely proportional to the distance to the center of the TC and the distance to the coastline; and the canopy height, diameter at breast height, and aspect where the tree stands significantly influence the response of the mangrove ecosystem GPP to TCs. However, the response varies for different mangrove community compositions, soil conditions, and planting densities as well as different frequencies and intensities of TCs, and they should be analyzed in detail. This study is expected to provide technical and data support for the protection of blue carbon in a subtropical island mangrove ecosystem in response to extreme events and post-disaster recovery. [ABSTRACT FROM AUTHOR]

Freshwater on islands represents a precious resource and highly vulnerable ecosystem. For monitoring freshwater, satellite remote sensing is efficient and has large-scale application. This study proposed a modified model of the quasi-analytical algorithm (ZSD-QAAv6m) to retrieve the water clarity of inland waters (>1 km2) across Hainan Island, China using Sentinel-2 multispectral instrument data. By adjusting the threshold of Rrs(665), the proposed model could accurately estimate water clarity with diverse optical properties on the island and avoid underestimation in moderately clear waters. Based upon this, the first spatiotemporal analysis of recent water clarity in Hainan Island was conducted. The results show that lake water clarity in the central region was generally higher (with average value of 1.4 m) than that of coastal regions (with average value of 1.2 m). Seasonally, the water clarity during the wet season was usually lower than that in the dry season, with average values of 1.1 m and 1.3 m across the island respectively. From 2017 to 2021, the proportion of water bodies with water clarity > 0.5 m increased from 60% to 100%. The overall spatial pattern of water clarity was correlated to the regional vegetation cover in Hainan Island, with higher clarity associated with higher vegetation cover in the central regions. The seasonal variation of water clarity may be attributed to heavy rainfall and runoff during the wet season; while the distinct annual variation may be benefited from the strengthened surface water protections in Hainan Province in recent years. This study provides a practical approach for evaluating the SDG 6.3.2 indicator in Hainan Island using remote sensed water clarity as a comprehensive water quality indicator and the findings could facilitate the island's water resource management and conservation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Triassic medium-grade metamorphism is recognized in Hainan Island, the eastern Paleo-Tethyan tectonic domain. • Amphibolite-facies metamorphism of the Mulantou Metamorphic Complex took place at ca. 250–235 Ma. • Peak metamorphic conditions reached 717–771 °C and 4.4–5.8 kbar, equivalent to a geothermal gradient of approximately 30 °C/km. • Mulantou Triassic amphibolite facies metamorphism resulted from collision between the South China and Indochina blocks after closure of the Paleo-Tethys. The Permian-Triassic tectonic evolution of Southeast Asia has long been a subject of considerable debate. Hainan Island in China is located at the junction of the South China and Indochina blocks adjacent to the Pacific (Philippine) Plate. Studies of metamorphic complexes in Hainan Island may shed lights on the Permian-Triassic tectono-thermal events of the eastern Paleo-Tethys. Among these complexes, the newly recognized Mulantou Metamorphic Complex is sporadically exposed in northeastern Hainan Island provides evidence for above-mentioned issues. In this paper, we present the result of a combined petrological and geochronological study of paragneisses in this complex. The paragneisses consist mainly of biotite, plagioclase, quartz, and rutile/ilmenite, with or without garnet, sillimanite, and muscovite. Textural relationships, mineral compositions, and thermobarometric calculations show that these paragneisses record peak metamorphic P − T conditions of 720–770 ℃ and 4.4–5.8 kbar. Zircon and monazite U − Pb dating by laser ablation–inductively coupled plasma–mass spectrometry indicates that metamorphism occurred at 250–235 Ma. Integrating published geochronological, geochemical, and structural data of Hainan Island and along the Jinshajiang − Ailaoshan − Song Ma suture zone, we infer that the Triassic amphibolite-facies metamorphism of the Mulantou Metamorphic Complex resulted from collision between the South China and Indochina blocks after closure of the Paleo-Tethys. [ABSTRACT FROM AUTHOR]

In June after the onset of the East Asian summer monsoon season, rainfall on the south side of Hainan Island (HNI) of China exhibits a trimodal pattern with an unusual peak near noon. A typical case of 20 June 2017 is chosen to analyze the mechanisms through a convection‐permitting simulation together with rainfall observations. Clockwise rotation in low‐level winds is found at and off the coast of south HNI, leading to maximum onshore southwesterly winds in the late morning that is closely linked to the diurnal variation of rainfall. The offshore diurnal variations of low‐level winds are tracked upstream and attributed to boundary layer inertial oscillations over the inland plain of Indochina Peninsula. In addition, a short wide gap comprised mostly of hills lower than 700 m is located across the higher Annamite Range along the east coast of the Peninsula, right upstream of HNI. Nocturnal boundary layer low‐level jet (LLJ) forming over the plain passes through the gap with significant acceleration due to gap channeling and downslope flow effects, reaching peak intensity off the Peninsula coast at around 09 local standard time (LST). The enhanced LLJ propagates downstream towards HNI and impinges on the mountains at around 12 LST when rainfall reaches peak there. As the inertial‐oscillation‐indued perturbation winds approaching the Island weaken and eventually reverse direction, lifting weakens and low‐level stability increases as descending motion develops offshore. Rainfall on the southern Island therefore dissipates in late afternoon. Plain Language Summary: In June after the onset of East Asian summer monsoon, rainfall on southern Hainan Island (HNI) of China has an unusual peak near noon. A representative case is numerically simulated at 2 km horizontal grid spacing and analyzed. It is found that the diurnal variation of rainfall is closely linked to diurnal variation of low‐level onshore winds which reach peak intensity around noon, and the source of such variations can be tracked upstream to the inland plain of Indochina Peninsula (ICP). Over the plain, afternoon boundary layer mixing causes low‐level wind speed minimum while boundary layer low‐level jet reaches peak speed in early morning due to inertial oscillation after the boundary layer flow becomes freed of the surface friction when mixing is shut off. The peak perturbation wind is advected toward HNI, and reaches the Island around noon. The lifting by mountains on southern HNI of the intensified low‐level winds causes peak rainfall there around noon. In the afternoon, the perturbation winds weaken and eventually reverse direction, causing dissipation of rainfall. In addition, the low‐level flow is accelerated when it passes through a gap in the coastal Annamite Range of ICP, amplifying the effect of inertial oscillations. Key Points: Diurnal clockwise rotation in the low‐level winds is found to be linked to an around‐noon rainfall peak on southern Hainan Island (HNI) in JuneDownwind advection of the upstream boundary layer inertial oscillations is responsible for the around‐noon rainfall peak over HNIA gap across Annamite Range of Indochina Peninsula amplifies and transports boundary layer inertial oscillation signals downstream [ABSTRACT FROM AUTHOR]

Monitoring disturbances in tropical forests is important for assessing disturbance-related greenhouse gas emissions and the ability of forests to sequester carbon, and for formulating strategies for sustainable forest management. Thanks to a long-term observation history, large spatial coverage, and support from powerful cloud platforms such as Google Earth Engine (GEE), remote sensing is increasingly used to detect forest disturbances. In this study, three types of forest disturbances (abrupt, gradual, and multiple) were identified since the late 1980s on Hainan Island, the largest tropical island in China, using an improved LandTrendr algorithm and a dense time series of Landsat and Sentinel-2 satellite images on the GEE cloud platform. Results show that: (1) the algorithm identified forest disturbances with high accuracy, with the R2 for abrupt and gradual disturbance detection reaching 0.92 and 0.83, respectively; (2) the total area in which forest disturbances occurred on Hainan Island over the past 30 years accounted for 10.84% (2.33 × 105 hm2 in total area, at 0.35% per year) of the total forest area in 2020 and peaked around 2005; (3) the areas of abrupt, gradual, and multiple disturbances were 1.21 × 105 hm2, 9.96 × 104 hm2, and 1.25 × 104 hm2, accounting for 51.93%, 42.75%, and 5.32% of the total disturbed area, respectively; and (4) most forest disturbance occurred in low-lying (<600 m elevation accounts for 97.42%) and gentle (<25° slope accounts for 94.42%) regions, and were mainly caused by the rapid expansion of rubber, eucalyptus, and tropical fruit plantations and natural disasters such as typhoons and droughts. The resulting algorithm and data products provide effective support for assessments of such things as tropical forest productivity and carbon storage on Hainan Island. [ABSTRACT FROM AUTHOR]

Hainan Island is the second-largest island in China and has the most species-diverse mangrove forests in the country. To date, the height and aboveground ground biomass (AGB) of the mangrove forests on Hainan Island are unknown, partly as a result of the challenges faced during extensive field sampling in mangrove habitats (intertidal mudflats inundated by periodic seawater). Therefore, this study used a low-cost UAV-LiDAR (light detection and ranging sensor mounted on an unmanned aerial vehicle) system as a sampling tool and Sentinel-2 imagery as auxiliary data to estimate and map the mangrove height and AGB on Hainan Island. Hainan Island has 3697.02 hectares of mangrove forests with an average patch area of approximately 1 ha. The results show that the mangroves on whole Hainan Island have an average height of 6.99 m, a total AGB of 474,199.31 Mg and an AGB density of 128.27 Mg ha−1. The AGB hot spots are located in Qinglan Harbor and the south of Dongzhai Harbor. The proposed height model LiDAR-S2 performed well with an R2 of 0.67 and an RMSE (root mean square error) of 1.90 m; the proposed AGB model G~LiDAR~S2 performed better (an R2 of 0.62 and an RMSE of 50.36 Mg ha−1) than the traditional AGB model G~S2 that directly related ground plots and Sentinel-2 data. The results also indicate that the LiDAR metrics describing the canopy's thickness and its top and bottom characteristics are the most important variables for mangrove AGB estimation. For the Sentinel-2 indices, the red-edge and shortwave infrared features, especially the red-edge 1 and shortwave infrared Band 11 features, play the most important roles in estimating mangrove AGB and height. In conclusion, this paper presents the first mangrove height and AGB maps of Hainan Island and demonstrates the feasibility of using UAV-LiDAR as a sampling tool for mangrove forests. [ABSTRACT FROM AUTHOR]

Most studies of temporal and spatial distribution characteristics for droughts and floods analysis were conducted only from the perspective of a single factor (precipitation), while ignoring the impact of the underlying surface on the formation of droughts and floods. Based on the daily precipitation data of 88 meteorological stations in Hainan Island from 1970 to 2019, 30 m resolution DEM data and land use dataset, etc., the precipitation Z index was used to evaluate the level of drought and flood in Hainan Island. The analysis results were revised by underlying surface data to evaluate the spatiotemporal characteristics of the drought and flood areas. The drought- and flood-prone areas in Hainan Island were divided. The results show that the overall drought areas show an obvious downward trend, while the flood areas present an increasing trend. The drought-prone areas throughout the year are more concentrated in the northeast of Hainan Island, while the flood-prone areas are mainly distributed in the eastern coastal areas. The drought- and flood-prone areas before and after the revision by the underlying surface were compared. It can be seen that the overall trend is relatively similar and obvious before and after the revision. The drought- and flood-prone areas before revision are 7.97 and 2.91 times larger than that after revision, respectively. Finally, combining climate and underlying surface factors, suggestions for drought and flood prevention are put forward. [ABSTRACT FROM AUTHOR]

As the world's largest reactive carbon reservoir, the ocean plays a critical role in global climate change. Among coastal plant ecosystems, mangroves have the highest carbon storage efficiency and are prone to the impact of anthropogenic activities. In this study, taking the mangrove wetland of Qinglan Bay as an example, we extracted information on mangrove coastal surface change from 1988 to 2020 based on multi-temporal Landsat remote sensing data through field ground surveys and laboratory analysis and used the InVEST model to calculate the spatial and temporal structure of blue carbon in the mangrove area to investigate the effects of mangrove change in an ecological restoration context. The result shows that the overall area of mangrove forests exhibited a decreasing trend from 1988 to 2020, and the area of mangroves decreased from 1559.34 ha to 737.37 ha of which 52.71% was transformed into aquiculture, construction, and farm land. Accordingly, the mangrove carbon sinks from 1988 to 2020 were significantly reduced and the carbon stock decreased at an annual tendency from 1,025,901.71 tons to 712,118.69 tons. With the implementation of mangrove restoration, the decline of mangrove forests has decreased since 2003, promoting the stabilization and enhancement of carbon sinks in the mangrove wetlands of Qinglan Bay. The results of this study provide a technical method to evaluate the carbon sink contribution of mangrove wetland restoration in Hainan Province, a scientific basis and methodological innovation to monitor the carbon sink of mangrove cover change in larger regions of China, a theoretical basis to select criteria for mangrove restoration, and a scientific and systematic management strategy for ecological and mangrove restoration on Hainan Island. [ABSTRACT FROM AUTHOR]

Hainan Island is located at the intersection of the India–Australian, Philippine–Pacific, and Eurasian plates. As a key component of Southeast Asia, constraints on the tectonic evolution of Hainan Island can help researchers to understand the evolutionary process of SE Asia more thoroughly. This study reports 960 new detrital zircon U–Pb ages of 8 samples from the Silurian, Pennsylvanian, and Middle Triassic strata on Hainan. Detrital zircon grains from the Silurian samples yield five dominant age populations of 460–420 Ma, 600–500 Ma, 1200–1000 Ma, 2000–1400 Ma, and 2700–2400 Ma. There are high similarities in age distributions between the Silurian and Pennsylvanian samples, but the Pennsylvanian samples exhibit a special age population of 360–340 Ma. The Middle Triassic samples have a relatively simple detrital zircon age distribution pattern with a dominant age peak at ca. 250 Ma and a subordinate age group of 390–360 Ma. The Silurian strata on Hainan Island mainly receive detritus from the South China Block and Eastern Gondwana, and detrital zircon grains from the Pennsylvanian samples were derived from the recycled strata on Hainan Island except that ca. 350 Ma grains came from the Early Carboniferous bimodal volcanic rocks near the Pennsylvanian sample site. Detrital zircons of the Middle Triassic samples are mainly derived from the ca. 250 Ma collision-related arc materials and the recycled strata. Based on detrital zircon geochronological data and previous results, we proposed a new tectonic model for the late Paleozoic tectonic evolution of Hainan Island. The Carboniferous drifting of Hainan Island northward resulted in a back-arc basin developed on central Hainan Island. At ca. 330 Ma, this back-arc basin turned into an oceanic basin, and this oceanic basin continued to develop during the Early–Middle Permian. Due to the closure of this oceanic basin since the late Middle Permian, the North Hainan finally collided with the South Hainan along the Bangxi–Chenxing tectonic belt and consolidated to form a unified Hainan Island again at ca. 250 Ma. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we analyzed population genetic diversity of Scylla paramamosain in Hainan Island of China based on COI gene sequence. Totally 92 individuals were collected from six localities: Haikou, Wenchang, Wanning, Sanya, Dongfang and Danzhou. A 761 bp fragment was sequenced, defining 32 different haplotypes. H4 was the most frequent haplotype, existing in all six localities, while the majority of haplotypes were rare ones, existing in only one or two individuals. Haplotype diversity (h) and nucleotide diversity (π) ranged from 0.625 to 0.914 and from 0.001 to 0.003, with an average of 0.841 and 0.002, respectively. Genetic distance ranged from 0.001 to 0.003 within localities and from 0.002 to 0.003 between localities. The AMOVA analysis indicated a low level of genetic differentiation among six localities (F ST = 0.0176, P > 0.05). Neutrality tests and mismatch analysis implied a potential population expansion event for this crab species. [Copyright &y& Elsevier]

High‐P (HP) eclogite and associated garnet–omphacite granulite have recently been discovered in the Mulantou area, northeastern Hainan Island, South China. These rocks consist mainly of garnet, omphacite, hornblende, quartz and rutile/ilmenite, with or without zoisite and plagioclase. Textural relationships, mineral compositions and thermobarometric calculations demonstrate that the eclogite and garnet–omphacite granulite share the same three‐stage metamorphic evolution, with prograde, peak and retrograde P−T conditions of 620–680°C and 8.7–11.1 kbar, 820–860°C and 17.0–18.2 kbar, and 700–730°C and 7.1–8.5 kbar respectively. Sensitive high‐resolution ion microprobe U–Pb zircon dating, coupled with the identification of mineral inclusions in zircon, reveals the formation of mafic protoliths before 355 Ma, prograde metamorphism at c. 340–330 Ma, peak to retrograde metamorphism at c. 310–300 Ma, and subsequent pegmatite intrusion at 295 Ma. Trace element geochemistry shows that most of the rocks have a MORB affinity, with initial εNd values of +2.4 to +6.7. As with similar transitional eclogite–HP granulite facies rocks in the thickened root in the European Variscan orogen, the occurrence of relatively high P−T metamorphic rocks of oceanic origin in northeastern Hainan Island suggests Carboniferous oceanic subduction leading to collision of the Hainan continental block, or at least part of it, with the South China Block in the eastern Palaeo‐Tethyan tectonic domain. [ABSTRACT FROM AUTHOR]

Our field-based geochemical studies of the Triassic, Jurassic and Cretaceous granitoids on Hainan Island indicate that their magmas had different geochemical affinities, changing from alkaline in the Triassic through ocean island basalt (OIB) in the Jurassic, to calc-alkaline in the Cretaceous. We show that these changes in the geochemical affinities of the Mesozoic granitoids on Hainan and in SE China reflect different melt sources and melt evolution patterns through time. Our new geodynamic model suggests that: (1) Triassic geology was controlled by flat-slab subduction of the palaeo-Pacific plate beneath SE China. This slab dynamics resulted in strong coupling between the lower and upper plates, causing push-over tectonics and contractional deformation in SE China. Flat subduction-induced edge flow and aesthenospheric uprising led to the production of high-K granites, syenites and mafic rocks. (2) Slab foundering, accelerated subduction rates and subduction hinge retreat in the Early Jurassic caused rapid rollback of the downgoing slab. Strong decoupling of the upper and lower plates resulted in pull-away tectonics, producing extensional deformation in SE China. Decompression melting of the upwelling aesthenosphere produced OIB-type melts, which interacted with the subcontinental lithospheric mantle (SCLM) to form A- and I-type granitoids. (3) Segmentation of the palaeo-Pacific plate in the Early Cretaceous resulted in steeply dipping slabs and their faster rollback, facilitating lithospheric-scale extension and oceanward migration of calc-alkaline magmatism. This extensional deformation played a significant role in the formation of metamorphic core complexes, widespread crustal melting and development of a Basin and Range-type tectonics and landscape evolution in SE China. [ABSTRACT FROM AUTHOR]

The distribution of mangroves is influenced by the environment. We aimed to understand the ecological adaptability of various mangrove species within the range of the exotic species, Sonneratia apetala Buch.‐Ham., in Dongzhai Harbor, Hainan Island, China. We used three niche breadth indexes (Simpson, Levins, and Shannon–Weiner) and two niche overlap indexes (Pianka and Levins) to quantitatively determine the niche characteristics of nine mangrove species. The results showed that the order of the niche breadth values of mangrove species was as follows: Aegiceras corniculatum (Linn.) Blanco > Kandelia obovata Sheue et al. > Bruguiera gymnorrhiza (L.) Poir. > Avicennia marina (Forsk.) Vierh. Hailanci > S. apetala > S. caseolaris (L.) Engl. > Rhizophora stylosa Griff > Ceriops tagal (Perr.) C. B. Rob. > B. sexangula (Lour.) Poir. Pearson correlation analysis revealed that the niche breadth of each population was significantly correlated with the importance value of the population in the whole sample (R1 = R2 = 0.771, R3 = 0.644, p <.05). The nine mangrove species were divided into three groups by Bray–Curtis cluster analysis; the groups were similar to the distribution of mangrove species in the natural state as determined by tide level. Niche similarity analysis showed that the niche similarity of most mangroves ranged between 0.5 and 0.8 and that the species pairs A. corniculatum–B. gymnorrhiza, A. corniculatum–Avicennia marina, and K. obovata–S. caseolaris were characterized by large niche similarity ratios. Although it had a moderate niche breadth, S. apetala had a relatively broad niche overlap with mangroves in the mid‐ and low‐tide zones (S. caseolaris, A. corniculatum, K. obovata, and Avicennia marina), a moderate overlap with B. gymnorrhiza and R. stylosa, only a slight overlap with C. tagal, and no overlap with B. sexangular. There was no obvious linear relationship between niche width and niche overlap of mangroves. Due to its inefficiency in utilizing certain resources and relatively high degree of resource selection, it seems likely that S. apetala will not pose a threat to the survival of native plants, let alone completely replace native species. [ABSTRACT FROM AUTHOR]

The late Triassic Baolun gold deposit hosted by Silurian phyllites is a large‐scale high‐grade gold deposit in Hainan Island, South China. The ores can be classified into quartz‐vein dominated type and less altered rock type. Three mineralization stages were recognized by mineral assemblages. The early stage, as the most important mineralization stage, is characterized by a quartz–native gold assemblage. The muscovite−quartz−pyrite−native gold assemblage is related to the intermedium mineralization stage. In late mineralization stage, native gold and Bi‐bearing minerals are paragenetic minerals. Microthermometry analyses show that the early mineralization stage is characterized by two types of fluid inclusions, including CO2‐rich inclusions (C‐type) and aqueous inclusions (W‐type). C‐type inclusions homogenize at 276–335°C with an averaged value of 306°C and have salinities of 1.0–10.0 wt% NaCl equivalent (mean value of 4.9 wt% NaCl equivalent). W‐type inclusions homogenize at 252–301°C (mean value of 278°C) with salinity of 4.0–9.7 wt% NaCl equivalent (mean value of 7.4 wt% NaCl equivalent). In intermedium mineralization stage, C‐type and W‐type inclusions homogenize at 228–320°C (mean value of 283°C) and 178–296°C (mean value of 241°C), with salinities of 2.4–9.9 wt% NaCl equivalent (mean value of 6.5 wt% NaCl equivalent) and 3.7–11.7 wt% NaCl equivalent (mean value of 7.7 wt% NaCl equivalent), respectively. No suitable mineral, such as quartz or calcite, was found for fluid inclusion study from late mineralization stage. In contrast, only aqueous inclusions were found from post‐ore barren veins, which yielded lower homogenization temperatures ranging from 168–241°C (mean value of 195°C) and similar salinities (2.6–12.6 wt% NaCl equivalent with averaged value of 7.2 wt% NaCl equivalent). The different homogenization temperatures and similar salinities of C‐type and W‐type from each mineralization stage indicate that fluid immiscibility and boiling occurred. The Baolun gold deposit was precipitated from a CO2‐bearing mesothermal fluid, and formed at a syn‐collision environment following the closure of the Paleo‐Tethys. [ABSTRACT FROM AUTHOR]

According to traditional biogeographic theory, historical contingency can influence soil microbial communities. Thus, we ask: are historical contingencies (soil profiles and geographic sampling locations), or other factors (seasonal changes and soil nutrients), important drivers of soil bacterial communities? This study used high throughput sequencing technology to investigate the soil bacterial compositions of rubber plantations at the local and geographic scales. Significant differences were detected in bacterial compositions between two study locations, Xishuangbanna and Hainan Island. Redundancy analysis showed that the most important factor driving bacterial composition was site location and total nitrogen, which explained 38.2 and 38.4% the total variance, respectively; this indicates that historical contingencies drive distinct bacterial communities in rubber plantation soils. At the local scale, there were also distinct differences in soil bacterial compositions between the dry and rainy season in both the Xishuangbanna and Hainan sites. Seasonal changes explained 13.6 and 41.4% of the total variation of soil bacterial composition in Xishuangbanna and on Hainan Island, respectively, whereas other factors had little effect on soil bacterial communities (p < 0.001). In conclusion, our results demonstrate that historical contingencies drive variation in bacterial composition at the geographic scale, whereas seasonal changes influence variation at the local scale. [ABSTRACT FROM AUTHOR]

Four new species, Caeculisoma allopenlineatus Xu & Jin sp. nov., Dambullaeus jianfengensis Xu & Jin sp. nov., Iguatonia seemani Xu & Jin sp. nov. and Iguatonia xinfengi Xu & Jin sp. nov. are described and illustrated based on larvae ectoparasitic on insects (Hemiptera) from Hainan Province, China. The genus Iguatonia is reported for the first in China. New data for Caeculisoma penlineatus Xu & Jin, 2019 are given. Keys to world species of larval Caeculisoma, Dambullaeus and Iguatonia are presented. [ABSTRACT FROM AUTHOR]