Rivers are crucial to biogeochemical cycles, connecting terrestrial, oceanic, and atmospheric systems. However, their ecosystems are increasingly threatened by extreme weather events. Here we used the environmental DNA approach to assess the impact of extreme drought-heatwave events on the aquatic plankton communities of the Yangtze River. We showed that an extreme drought-heatwave event reduced the alpha diversity of communities, increased their beta diversity, and simultaneously simplified and destabilized community network structure. This event also shifted the dominant algae taxa from Bacillariophyta to Cyanobacteria, accompanied by increases in organic carbon and labile organic carbon contents. Globally, temperature rises during this extreme drought-heatwave event are more pronounced in high-latitude regions, likely amplifying impacts on river ecosystem biodiversity and stability. Our findings highlight the vulnerability of river ecosystems to extreme events and underscore the need to mitigate climate change's effects on river ecosystems.

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Achieving the harmonious development of the “social-ecological” system is a crucial aspect of the global sustainable development goals. Landsenses ecology is an emerging concept that emphasizes sustainable land use planning and comprehensive management. Islands serve as ideal study areas setting for studying the landsenses ecology due to their vulnerability as ecosystems exposed to significant human activities. To assess the condition and spatial distribution of landsenses ecology, we established a quantitative evaluation framework that encompassed eight factors across two perceptions - physical and psychological. Our study focused on two islands situated in southeast China, which, despite their proximity, demonstrate remarkable differences in terms of natural and economic characteristics. The results revealed a significant spatial heterogeneity in the landsenses ecological condition on both islands. Nan'ao island (NAI) exhibited higher values for physical (0.5) and psychological (0.243) perceptions compared to Dongshan island (DSI), which was primarily attributed to varying natural environments and topographic factors. Notably, elevation and slope demonstrated strong correlations with landsenses ecological condition, acting as critical determinants of island development. Finally, using beaches as an example, we examined the impact of landsenses ecological conditions about the tourist resources of the islands. This study contributes to the development of scientifically informed urban and tourism planning processes by providing decision-makers with valuable insights.

Coastal soil carbon stock is critical owing to the coexistence of terrestrial and marine carbon sinks and undergoes drastic changes under complex factors. Here we conduct surface soil organic carbon (SOC) stock mapping in northern China’s coastal areas in 2020 and 2010 based on large-scale field survey, remote sensing, and land cover data. Our results indicate that a 100 m resolution is the optimum mapping resolution for its good simulation accuracy and precise spatial details. The surface SOC stock and density in 2020 increased by 39.19% and 37.82%, respectively, compared with those in 2010 under extensive ecological restoration. The SOC densities of forests, grasslands, croplands, wetlands, and built-up areas increased by 72.58%, 74.25%, 41.39%, 4.58%, and 26.30% from 2010 to 2020, respectively. The study determines the optimum mapping resolution and denotes the positive effects of ecological restoration on coastal soil carbon.

The human-land interrelations in archipelagic areas naturally present spatial heterogeneities at multiple scales. Revealing the archipelagic human-land spatial interrelations is important for improving the understanding of intrinsic relationships among natural contexts, human activities, and ecological conditions on islands and further enriching the research on human-land interrelation. In this study, Shengsi Archipelago, a China's typical archipelago with highly spatial heterogeneities in natural, anthropogenic, and ecological factors, was selected as the study area, and field survey and remote sensing served as the data source. Nine types and 23 sub-types of human activities were identified over the archipelago, and human activity development indices were established to measure the intensities and spatial patterns of human activities based on the area and influencing coefficients. The spatial interrelations among natural, anthropogenic, and ecological factors were then analyzed using regression analysis at island scale, correlation analysis at grid scale, and canonical correspondence analysis at the dual scales. Results indicated that natural factors explained 22.30% and 7.30% of the spatial variances of human activities at island and grid scales, respectively; they exerted influences in two levels, namely, human activities as a whole and different types of human activities, and human activities did not show exactly consistent spatial inclinations across the two levels. Natural contexts explained 23.40% and 2.90% of the spatial variances of ecological conditions at island and grid scales, respectively. By contrast, human activities played the dominant role in the island ecosystem and explained 48.10% and 51.90% at island and grid scales, respectively; they influenced the spatial pattern of ecological conditions mainly through a synergistic way, and the influences were consistent across the two scales. The study validated the following hypothesis that human activities can spread over the archipelago in spite of the limits of natural contexts and become the main driving factor of the island ecological evolution.

Identifying and quantifying the impacts of human activity on island plant diversity can help inform their management. Here, we examined the spatial pattern of plant diversity across 11 inhabited islands near to, but outside, the Yangtze River Estuary in the Shengsi Archipelago, China, that represent a diverse range of environmental conditions and human activity levels. We quantified six factors (island morphology, landscape, proximity, ecology, terrain, and soil) and 30 environmental indicators, with different levels of human influence. Regression and canonical correction analyses were used to determine the effects of various factors on the spatial distribution of trees, shrubs, and herbs at four regional scales: sample, island, sub-archipelago, and archipelago. We recorded 287 vascular species belonging to 201 genera at 93 sampling sites in Shengsi, of which 10 invasive alien species at 60 sampling sites were recorded. The plants showed a diverse spatial distribution pattern at the sampling site scale because of the synergistic influence of multiple environmental factors. From the sub-archipelago and island scales, area and isolation are the most critical factors affecting the richness and diversity of shrubs and herbs. The diversity and distribution of trees is highly dependent on human residents, and herbs show strong adaptability on barren landscapes. At the site scale, when collinearity among environmental factors was eliminated, we found that soil bulk density and salinity were critical factors driving the distribution of shrubs and herbs, respectively.

海岛特殊的地理位置和复杂的外界干扰,造就了其脆弱的生态系统;在日益增强的人类活动干扰下,海岛景观格局异质性增强,进而产生一系列生态效应.采用景观和生态效应指数,选择我国南方典型海岛——东山岛和南澳岛作为研究区,探究海岛景观格局的空间异质性;选择植被、土壤和地表水热条件三个重要的生态效应指标,从景观、海岛和区块三个尺度分析其对景观格局的响应状况.结果表明,从景观尺度来看,人工景观在各个景观指数和生态效应指标上相对自然景观都表现出较差的状态;在海岛尺度上,两个海岛尽管距离较近,但由于自然条件和海岛发展定位的差异,景观格局和生态效应都呈现较大的差异,南澳岛无论是景观格局还是生态效应都优于东山岛;在区块尺度上,两个海岛的景观格局和生态效应指标都呈现明显的空间异质性;海拔、坡度和距岸线距离对植被指数表现出显著的正相关性,对土壤和地表水热指数呈负相关性.研究结果揭示了 自然条件和人类活动对海岛景观格局的影响,并阐明了不同尺度下海岛生态系统对景观格局的响应特征,对海岛生态修复和空间规划具有实践意义.

Measuring the landscape pattern from a three-dimensional perspective is of great significance for comprehensively revealing the complex spatial characteristics of island ecosystems. However, the archipelago composed of rocky islands has received little attention as its three-dimensional landscape characteristics are difficult to quantify. This study took the largest archipelago in China, the Zhoushan Archipelago, as the study area and constructed an island landscape pattern evaluation model from a dual-three-dimensional (dual-3D) perspective. The model divided the island into upper and lower layers, namely the surface landscape based on topography and the landscape elements above the surface (i.e., vegetation and buildings), and then evaluated their landscape patterns from a three-dimensional perspective, respectively. The landscape pattern model based on a dual-3D perspective and multiple scales achieved excellent results in the archipelago. First, the island landscape pattern was evaluated from three-dimensional perspectives, including human interference, landscape fragmentation, vegetation space, and building space. Second, landscape indices such as the human interference three-dimensional index (HITI), the landscape fragmentation three-dimensional index (LFTI), the vegetation three-dimensional index (VTI), and the building three-dimensional index (BTI) established at multiple spatial scales revealed spatial heterogeneity within and between islands. Environmental factors such as elevation, slope, and island area exhibited significant correlations with them. There were significant differences in landscape pattern indices between the two-dimensional (2D) and the three-dimensional (3D) perspectives, and high values were mainly distributed in areas with significant topographic changes and larger islands. In addition, as the evaluation unit increased, the landscape indices increased, and HITI became more responsive to the transitions from 2D to 3D, while LFTI was the opposite. Therefore, the multiscale landscape pattern measurement of China’s largest archipelago based on high-resolution remote sensing was carried out from three-dimensional perspectives to accurately reveal the spatial heterogeneity.

Soil quality of coastal wetlands plays an important role in maintaining biological productivity, improving environmental quality, and promoting plant and animal health. Landscape pattern is the major factor affecting variations in soil quality of coastal wetland. However, the influence of landscapes on spatial variations in soil quality has not been fully explored in coastal wetlands with highly fragmented landscapes. Here, we established a composite indicator of soil quality of coastal wetland, used a series of analysis methods to explore the spatial characteristics of soil quality of coastal wetland and the intrinsic relationships between soil quality and landscape factors, and quantified the landscape factors affecting the spatial variation of soil quality. Chongming Island, a typical estuarine island coastal wetland in China, was selected as the study area. The results showed that coastal wetland soil quality had distinct spatial variations, and significant correlations were observed between soil quality indicators and landscape factors. Key landscape factors, including distance to coastline (DTC), distance to human-related landscape types (DTH), number of landscape types (NLT), natural index of landscape (NIL), number of landscape patches (NLP), total edge of landscape patches (TELP), net primary production (NPP), normalized difference vegetation index (NDVI), soil salinity index (SSI), and normalized difference build-up and bare soil index (NDBSI), were identified and quantified at the optimal spatial evaluation units. Among the landscape types, woodlands and farmlands showed better soil quality and landscape conditions in coastal wetlands. Among the landscape pattern factors, landscape function factors, rather than composition and structure factors, had a greater impact on the spatial variation of coastal wetland soil quality. The soil quality was good at positions with high DTC and NDVI and low DTH and SSI. These findings highlighted that landscape factors NDVI (19.93%), SSI (15.93%), DTC (15.28%), and DTH (11.16%) contributed the most to the spatial variation in soil quality on Chongming Island. This study reveals the intrinsic correlations between soil quality and landscape, and provides a reference for maintaining the coastal wetland ecosystems.

The global population and social economy are highly concentrated in the coastal zone. This region is being subjected to rapid human development. The coastal zone is located at the intersection of marine and terrestrial ecosystems in an ecologically complex environment. Hence, its original landscape patterns have undergone substantial alterations. The present study used a comprehensive framework to evaluate landscape ecological condition and sensitivity indices based on landscape composition, configuration, and function in the coastal zone of the Shandong Peninsula over the past 30 years. Eight evaluation units between 100 m and 10 km were employed to understand the Vulnerability scale effects of landscape ecological condition and sensitivity along the scale change. Between 1990 and 2020, the ecological condition and sensitivity of the coastal zone of Shandong Peninsula initially decreased and then gradually increased. The total evaluation demonstrated a trend of initial decrease and subsequent increase with evaluation scale. It was determined that 1 km was the optimal scale for landscape ecological sensitivity evaluation. The present research indicated that the evaluation of landscape ecological condition and sensitivity provides a technical reference for optimizing spatial development patterns in the coastal zones of Shandong Peninsula as well as other regions.

Driven by global changes and human activities, the sediment source/transport, and riverbed erosion and deposition pattern of the Yangtze River Basin are undergoing continuous adjustments, which influence both magnitude and property of fluvial sediment to the estuary. In order to explore sediment transport and correlated topographic changes of the Yangtze River Estuary within 40 years in response to variations of fluvial sediment discharge from the upstream basin, this study uses sediment grain size trend models and multi-year zonal analysis methods to predict temporal and spatial variations of morphological changes within the Yangtze Estuary, based on grain size data and topographic data from 1980 to 2020. The results show that sediments converge toward the center of the channel within the northern branch, and a deposition center forms close to the south and north channel diversion area within the southern branch, consistent with the morphological changes between 2012 to 2020 calculated from sea maps, validating the effectiveness of the grain size trend model in predicting morphological changes within the Yangtze River Estuary. The results of the multi-year zonal analysis show that: 1980—2003 was characterized by a high volume of fluvial sediment discharge, and the entire estuary area was dominated by deposition with slightly finer sediment. Fluvial sediment discharge experienced a rapid decrease from 2003 to 2012, while the estuary area was still dominated by deposition before 2009 with similar grain size. 2009—2012, however, was a transitional period when erosion and sediment coarsening started to appear out of the estuary, although limited to small areas. From 2012 to 2020, large-scale erosion and grain size coarsening occurred widely in the estuary, and a significant correlation was found between the particle size and the magnitude of erosion. Our study shows that high-resolution zonal analysis can effectively catch the local morphological change signals in the Yangtze River Estuary. In the past 40 years, the Yangtze River Estuary has changed from deposition-dominant mode to partially erosion mode, and it may face continuous coastal erosion in the future.