Miaodao Archipelago Research Articles

Ecological characteristics and seasonal changes of macrozoobenthos in the waters of Miaodao Archipelago, China

To understand the macrozoobenthic community composition and spatial-temporal distribution characteristics of macrobenthos in the waters of Miaodao Archipelago, Yantai, Shandong and its response to habitat changes, we conducted surveys of macrobenthos and environmental elements in the waters of Miaodao Islands in May (spring), August (summer), and October (autumn) in 2022. Results showed that a total of 127 macrozoobenthic species were recorded, with Mollusca and Annelida (Polychaeta) as the dominant taxa, consisting of 47 and 45 species, respectively. The key dominant species included Sternaspis chinensis, Glycinde bonhourei, Moerella hilaris, and Amphioplus (Lymanella) japonicus. The average annual density and biomass of macrozoobenthos were 190 ind·m-2 and 28.69 g·m-2, respectively. There was no significant seasonal differences in density and biomass. The Shannon diversity index (H), evenness index (J), and richness index (D) averaged 3.10, 0.90, and 2.40, respectively. Cluster analysis results showed low similarity coefficients of community among the three seasons, suggesting a distinct distribution pattern. Factors such as bottom seawater temperature, chlorophyll a, nutrient, sediment grain size, and organic matter content could significantly influence the structure and diversity of macrozoobenthic community. Compared with historical research data, the Changdao National Wetland Nature Reserve and the implementation of enclosure aquaculture have led to notable changes in the dominant species of macrobenthos. Specifically, there was a noticeable decline in both density and H, and an increase in biomass and J. Additionally, body size of benthic fauna was transitioning from small to big.

Estimating soil organic carbon and total nitrogen across inhabited and uninhabited islands based on dual simulations in the entire- and sub-areas

Soil total organic carbon (TOC) and total nitrogen (TN) mapping methods have been developed for different ecosystems; however, little attention has been paid to archipelagos comprising inhabited and uninhabited islands. In this study, we proposed a method of dual simulations in the entire- and sub-areas to adequately improve the simulation accuracy of soil TOC and TN in the archipelago. A typical archipelago, Miaodao Archipelago, was selected to demonstrate the method. The dual simulations comprehensively considered the common characteristics of the entire-area and the unique conditions of each sub-area in the archipelago. Through the dual simulations, the accuracy can be viewed in three hierarchies: the entire area (the first hierarchy), the inhabited and uninhabited islands (the second hierarchy), and the single island (the third hierarchy). The simulation accuracies for TOC were increased by 12.03%, 12.03%, and 16.94% in the first, second, and third hierarchies, respectively, compared with the baseline, and those for TN were increased by 7.13%, 9.21%, and 14.72%, respectively. The lowest normalized root mean squared errors for TOC and TN were 0.114 and 0.105, respectively, which were similar to those reported in previous studies that achieved high simulation accuracy in other areas. Considerable differences in soil TOC and TN existed across the inhabited (39.95 g/kg TOC and 3.61 g/kg TN) and uninhabited (63.42 g/kg TOC and 7.08 g/kg TN) islands, which were driven by the great differences in natural conditions and human activities across the two sub-areas. The dual simulations contributed to the further improvement of simulation accuracy in soil mapping, providing a practical method for soil TOC and TN estimation in the archipelago, and revealing the spatial differences in soil TOC and TN across the inhabited and uninhabited islands.

Composition and Distribution of Microeukaryotic Communities in the Surface Sediments of Five Geographic Regions of Bohai Sea Based on 18S rDNA Amplicon Sequencing

The Bohai Sea is a semi-enclosed shallow water that is influenced by both natural and anthropogenic stressors. However, the microeukaryotic communities and environmental factors that affect them in different regions remain largely unclear. We investigated microeukaryotic communities in surface sediments from five geographic regions using high-throughput sequencing of the 18S rDNA gene. The Miaodao Archipelago, Yellow River Estuary, and Central Bohai Sea had the highest Shannon and Simpson indices of the eukaryotic communities, while the Yellow River Estuary exhibited the highest Chao1 index. The microeukaryotic communities in surface sediments were mainly composed of Dinoflagellata, Bacillariophyta, Ciliophora, Cercozoa, and Protalveolata. Thalassiosira has a relatively high abundance at the Liaodong Bay and Central Bohai Sea, possessing the proportion of 41.70% and 38.10%, respectively, while Gonyaulax was the most abundant taxa in the Bohai Bay, occupying a proportion of 57.77%. Moreover, a negative correlation between diatoms and dinoflagellates was observed. Phosphorus, nitrogen, salinity, temperature, and silicate were major environmental determinants of microeukaryotic composition. Microeukaryotic communities in the surface sediments, especially for the composition and ratio of diatoms to dinoflagellates, reflected the environmental quality of marine ecosystems. Overall, these microeukaryotic community compositions provide a reliable indicator for monitoring the level of marine eutrophication in the Bohai Sea.

Non-negligible contribution from coastal erosion to sedimentation around the archipelago: A case study of Miaodao Archipelago

The Miaodao Archipelago, located in the southern Bohai Strait, serves as a major route for the exchange of energy and materials between the Yellow and Bohai seas and is distinguished by a complicated hydrodynamic environment and provenance. Based on the grain size and elemental data of 107 surface sediment samples from the archipelago waters, and 58 coastal erosional sediment and bedrock samples, this study investigated the factors influencing the geochemical elemental distribution, discusses the provenance of the surface sediments and relative contributions, as well as proposes a sediment source–sink model for the region. The distribution of major and trace elements in the surface sediments, typically characterized by “high in the north, low in the south” patterning (except for SiO2, Ba, and Sr), with their contents primarily controlled by the input of terrestrial materials. The surface sediments in the study area are separated into the geochemical subdivisions of north and south. The main provenances of the study area include the Yellow River, the nearshore Miaodao Archipelago, and the north side of nearshore Penglai, whose sediments were transported under the combined action of the Shandong Peninsula's tidal current, waves, and longshore current. Deposition occurred under the capturing action of the archipelago. The relative contributions of the three provenance areas were 74.7%, 15.5%, and 9.8%, respectively; the relative contribution of coastal erosion reaches 1/3 of the river. Studies have demonstrated that the contribution of coastal erosion provenances to sea surface sediments is non-negligible, and in fact, it may even be quite important; thus, in the context of decreasing riverine inputs to the sea and enhanced coastal erosion processes, the contribution of coastal erosion requires special attention.

Acoustic Presence of Cetaceans in the Miaodao Archipelago, China.

Once an important cetacean habitat, the Miaodao Archipelago has been altered by human-induced disturbances over several decades. While cetacean diversity is known to have decreased, no recent data on species diversity around Miaodao are known to exist. Capitalizing on the high vocal activity of cetaceans, three passive acoustic surveys, including towed and stationary types, were undertaken to detect the presence of species-specific vocalizations in May 2021, October 2021, and July 2022, as most cetacean sightings occurred during May and August in recent years. The results revealed that the East Asian finless porpoise is the sole cetacean species that can be reliably observed around the archipelago, as no other species were detected. The acoustic data also revealed potentially clumped distributions of finless porpoises with some seasonal variation. While not acoustically detected during any of the surveys, humpback whales, minke whales, and killer whales have been visually sighted in the region. The lack of acoustic detection of these species suggests that they are likely to be temporary visitors to the region, or at least exhibit strong seasonality in their presence within the region. These new data provide the latest snapshot of cetacean presence around the Miaodao Archipelago that can help inform future research and conservation.

Vulnerability of mariculture areas to oil-spill stress in waters north of the Shandong Peninsula, China

Mariculture plays an important role in providing humans with a stable source of aquatic products, but oil spills have both real and perceived effects on mariculture facilities and stocks. This study developed an oil-spill environmental-vulnerability model to assess and map the vulnerability of mariculture areas by integrating various indicators of exposure, sensitivity, and adaptability into a composite index using the analytic hierarchy process (AHP) and the geographic information system (GIS). This study aimed to assess the spatial heterogeneity of mariculture vulnerability to oil-spill stress in waters north of Shandong Peninsula, China. Weighting indicated that sensitivity was determined by the natural environment in which each mariculture area was located, while exposure was determined by potential oil-spill sources. Together, sensitivity and exposure strongly affected the vulnerability of various mariculture areas, while adaptability, determined by oil-spill response capability, had less effect on vulnerability. The waters north of Shandong Peninsula were divided into four sub-zones for ease of description. The results showed obvious spatial variations in oil-spill vulnerability among the zones; the zone in which the Miaodao Archipelago was located showed extremely high vulnerability to oil spills, in contrast to the other zones. This study quantitatively analyzed the vulnerability of mariculture areas to help clarify the effects of oil-spill accidents, and the results highlighted the need to enhance adaptability to reduce vulnerability, thereby benefiting marine aquaculture stakeholders who are actually beset by oil-spill risks.

Land Subsidence Assessment of an Archipelago Based on the InSAR Time Series Analysis Method

The lack of resources on islands leads to their extremely rapid development, and this can result in frequent geological disasters involving island subsidence. These disasters not only destroy the ecological environment and landscape of islands but also pose massive threats to the safety of residents’ lives and property and can even affect the country’s maritime rights and interests. To meet the demands of island stability and safety monitoring, in this study, we propose a large-area, full-coverage deformation monitoring method using InSAR technology to assess island subsidence based on a comprehensive analysis of conventional monitoring techniques. The working principle and unique advantages of InSAR data are introduced, and the SBAS InSAR key interpretation processing flow are described in detail. The GPU-assisted InSAR processing method is used to improve the processing efficiency. The monitoring results showed that the southern island group of the Miaodao Archipelago was relatively stable overall, with an annual average deformation rate of 3 mm. Only a few areas experienced large-magnitude surface deformation, and the maximum annual deformation magnitude was 45 mm. The time series deformation results of the characteristic points of the five inhabited islands in the southern island group showed that the subsidence trends of the two selected points on Beichangshan Island (P1 and P2) were slowly declining. The P3 point on Nanchangshan Island experienced a large deformation, while the P4 point experienced a relatively small deformation. The selected points (P5, P6 and P7) on Miaodao Island, Xiaoheishan Island and Daheishan Island were stable during the monitoring period. InSAR data can be used to accurately identify the millimetre-scale microdeformations experienced by island groups, thus demonstrating the high-precision deformation monitoring capability of these data. In addition, the accuracy of these data can meet the needs of island and archipelago subsidence monitoring, and the proposed method is an effective means to monitor the spatial deformation of island targets. This study is conducive to further enriching and improving island stability and safety monitoring technology systems in China and to providing data and technical support for identifying and mastering potential island risks, protecting and utilizing islands and preventing and reducing disasters.

Island carrying capacity for three development types: ecological resource, agricultural production, and urban construction

The evaluation of island carrying capacity is the premise for conducting the island spatial planning and can contributes to guiding island ecological conservation and socioeconomic developments. In this study, the island carrying capacities were evaluated for the three major development types, namely, ecological resource, agricultural production, and urban construction, based on the quantity and quality. The occupancy and vacancy rates of island carrying capacity were measured in different scenarios. Miaodao Archipelago and Dongtou Archipelago in China were selected as the study area to demonstrate the evaluation. The former is constituted all by spatially isolated rocky islands, while the latter is featured by the coexistence of the sandy and rocky islands and the connection with the mainland by bridges. The results indicated the high variances of occupancy and vacancy rates of island carrying capacity at multiple spatial scales. Across the two archipelagos, climate conditions, island composition, and spatial connections with the mainland controlled the spatial variance at this scale. For different types of islands, the sandy island presented distinctly higher occupancy and vacancy rates for agricultural production than the rocky islands. At the single island scale within the same archipelago, the developments of agricultural production and urban construction distinctly increased with the increase in the island area. The dependency of island constructions on the external world in Dongtou Archipelago was higher than that in Miaodao Archipelago. Meanwhile, the difference in traffic conditions between the two archipelagos did not distinctly influence the food dependency on the external world. Then, practical suggestions in terms of quantity control and quality promotion were proposed to improve the island carrying capacity.

Island development suitability evaluation for supporting the spatial planning in archipelagic areas

The study of island development suitability can provide important reference for island ecosystem-based management and sustainable development, as well as technical foundation for land development suitability evaluation and spatial planning in other areas. In this study, two typical China's archipelagos, namely, Miaodao Archipelago and Dongtou Archipelago, were selected to demonstrate the study. The carrying capacities of the three major development types, that is, ecological conservation, agricultural production, and urban construction, served as basic data; the controlling factors of island development suitability were identified in aspects of terrain, sea, and soil, and their influences on the three development types were separately measured in the two archipelagos and on different types of islands; and the island development suitability index (IDSI) was established for each of the three development types. Then, four schemes, namely, Schemes A–D, were designed based on the IDSIs and for purposes of free development, ecological conservation, agricultural production, and coordinated development, respectively, to conduct the island functional zoning, and the optimum scheme was finally selected. The results indicated that the influence natures and degrees of controlling factors showed distinct spatial heterogeneities across different archipelagos and across different types of islands within the same archipelago. Area proportions of the planned zones varied in different schemes for different purposes, and the optimum scheme was generated by assigning Schemes A, B, C, and D to the reclamation areas within the islands, the uninhabited islands, the sandy island, and the remaining islands, respectively. The present study validated two hypotheses: First, the factual influences of controlling factors on the land development suitability varied across different areas and might not be in accordance with the empirical cognitions. Second, the method of multiple schemes for different development purposes could contribute to solving the problem of disconnection of land development suitability with spatial planning.

Ecosystem services assessment and sensitivity analysis based on ANN model and spatial data: A case study in Miaodao Archipelago

Ecosystem services (ESs) assessment is an important basis for the island protection and utilization plan development. The application of artificial neural network (ANN) to ESs assessment is a new attempt. Herein, an ANN model for the assessment of 5 ESs including carbon sequestration (CS), habitat quality (HQ), nutrient retention (NR), sediment retention (SR), and water yield (WY) of Miaodao Archipelago is established by taking the advantages of InVEST model and the powerful spatial analysis function of the geographic information system (GIS), as well as the self-learning and self-adaptive characteristics, and prediction function of ANN. The independent sample test shows that the correlation coefficient between the model prediction value and InVEST model simulation value is 0.88 (P < 0.001), and the average absolute error of the simulation is 10.33%. The 5 ESs of the Miaodao Archipelago in 2019 was then simulated using the trained model. The comparison with the corresponding data in 2010 suggests that CS, SR and HQ are in decline, while WY is in upward. The impacts of land use on ESs are then analyzed with the ecosystem service change index (ESCI) in different land use scenarios. An ANN model based quantitative method for evaluating the sensitivities of ecosystem service (ES) to typical environmental factors is proposed. The modeling results suggest that the ANN based model can accurately quantify the importance of different environmental factors to the island ESs, and give the comprehensive impact of multiple factors on the ESs. Therefore, the ANN model combined spatial data analysis provides an important means for ESs assessment and sensitivity analysis.

Stable Isotope Analysis of Food Web Structure and the Contribution of Carbon Sources in the Sea Adjacent to the Miaodao Archipelago (China)

The littoral zones around archipelagos are highly productive coastal habitats that serve as biodiversity hotspots and provide valuable ecosystem services that are different from those of the pelagic and profundal zones. The littoral zone has complex basal carbon sources from different primary producers and is an important ocean–land transition area. Macroalgae are the main primary producers of the littoral zone, but their carbon contribution to consumers is rarely studied. Basal carbon sources determine the structure of the food web. In order to determine the contribution of basal carbon sources and the food web structure of the littoral zone, we used carbon and nitrogen stable isotope techniques and a Bayesian mixing model to study the autumn benthic food web in the sea adjacent to the Miaodao Archipelago. The potential carbon sources of the benthic food web biota in the sea adjacent to the Miaodao Archipelago in autumn are mainly algae (including phytoplankton and macroalgae) and SOM, but the contribution of POM is low. Macroalgae may play a more important role in the littoral zone benthic food webs. Although there are certain uncertainties in the model results, invertebrates and fish have obvious differences in their use of carbon sources. The trophic importance of different primary producers varies with functional feeding groups, and the resource utilization of different functional feeding groups may have certain spatial characteristics.

Sea-level changes in the Bohai Sea, northern China, constrained by coastal loess accumulation over the past 200 ka

Loess sequences are widely distributed in semi-arid regions around the world, and are sometimes also located in coastal zones. The accumulations of coastal loess provide a valuable record of both climate and sea-level changes. Here we report sedimentological and high sampling resolution luminescence dating evidence for such changes from two loess sequences from the Shandong Peninsula and Miaodao Archipelago near the coast of Bohai Sea in northern China. Both the quartz optically stimulated luminescence (OSL) and K-feldspar post-infrared IRSL (pIRIR290) signals show consistent and satisfactory luminescence characteristics up to ∼100 ka, while the K-feldspar pIRIR290 ages provide age control up to ∼200 ka and are in stratigraphic order. With this fully independent age model, our results reveal that coastal loess accumulation is episodic with a high variability in apparent accumulation rates. After comparing with global and regional sea-level records, we find that the intervals with high accumulation rates coincide with global low sea-level stages, and that the loess sedimentary hiatuses indicated by nearly zero or very low accumulation rates at one site mainly correspond to global high sea-level stages, indicating the dominant role of global sea-level changes on coastal loess accumulation in the study area. We therefore conclude that regional marine regression mainly occurred during MIS 6, and MIS 5b to MIS 2, with extremely low regional sea levels possibly around 150 ka, 70–60 ka and 37–24 ka, while high sea-levels occurred during MIS 5e–5c and MIS 1. This study implies that coastal loess deposits with a good chronology could be used to constrain the timing of regional sea level change.

Landscape changes and their ecological effects of Miaodao Archipelago with human disturbances and under natural conditions in the past 30 years

The modern landscape patterns of islands usually show obvious spatial heterogeneity and complex ecological effects due to the vulnerability of ecosystems with natural characteristics under increasing human activities. In this work, we studied the variation in landscape pattern of the Miaodao Archipelago in Bohai Sea, North China, from 1990 to 2019, and an evaluation index system was established to explore the impacts of natural conditions and human disturbances on the ecological effects in the pressure-state-response (PSR) framework. Empirical analysis was conducted on the natural conditions, human disturbances, and ecological effects. The results show that forest was the main component of the landscape pattern in the archipelago. Both of the areas of forest and construction land were increasing, and the areas of cropland and grassland were declining. Other landscape types changed slightly, and the landscape fragmentation was increasing. The natural condition exhibited positive effects while human disturbance showed negative effects on the local ecology. Human disturbances come mainly from shoreline use while the natural conditions were mainly from the elevation change. The ecological effects were resulted mainly from the net primary productivity and water yield.

Valuing tourists’ willingness to pay for conserving the non-use values of marine tourism resources: a comparison of three archipelagic tourism destinations in China

The conservation of marine tourism resources based on the public’s preference for non-use values is important to the sustainable development of marine tourism. The objectives of this article are to explore the willingness to pay (WTP) for the non-use values of marine tourism resources and how such WTP differs among types of marine tourism resources in China. A contingent valuation study was undertaken at three archipelagic tourism destinations: the Miaodao Archipelago, with beaches and maritime geological heritage (Yellow Sea and Bohai Sea areas); the Zhoushan Archipelago, with beaches and maritime culture (East China Sea area) and Sanya and nearby islands, with beaches and coral reefs (South China Sea area). Tourists’ WTP varies by resource type, among which the WTP for the above six subsamples ranged from ¥192.93 to ¥373.16, confirming the existence of the non-use values of marine tourism resources in China. These results not only provide references for determining priorities for protecting marine tourism resources but also suggest that policymakers can focus on the more attractive resources to raise conservation funds, thus promoting the realization of general conservation objectives. Furthermore, this article offers novel insights into the validity and reliability test of contingent valuation method (CVM) studies.

Which factor determines the spatial variance of soil fertility on uninhabited islands?

Uninhabited islands serve as a natural and unique laboratory for the study of soil fertility under varying natural conditions and potential anthropogenic influences, and how the soil fertility spatially varies and which factor determines the spatial variance remain to be studied. In this study, a total of 15 uninhabited islands in Miaodao Archipelago, a typical archipelago in northern China, were selected to demonstrate the study. The soil fertility was represented by seven soil factors and a composite index, namely, soil fertility indicator (SFI). Different environmental factors that covered natural and anthropogenic aspects were identified at island and local scales, and the spatial pattern of soil fertility responding to the environmental factors was analyzed. Then, the influences of different environmental factors on the spatial variances of soil fertility at the dual scales were quantified. Results revealed that the soils in the study area had considerably higher values of total carbon, total nitrogen, organic matter, available phosphorus, and available potassium compared with the soils on other China’s islands, the recognized standards, and the national and regional mean values, indicating the extremely high fertility. Great spatial differences in the soil fertility were observed among different islands and sampling sites. At island scale, the island isolation, which was represented by the distance to the inhabited islands and the mainland (DTI), determined the spatial variance of soil fertility. The SFI distinctly increased with the increase in DTI, which could be explained partly by the isolation from human activities and the vegetation condition at island scale, and partly by the cross-scale influence from altitude (Al). At local scale, Shannon-Wiener index (H’), Al, slope (Sl), and distance to the shoreline (DTS) showed clear positive correlations with SFI. The Al and DTS determined the spatial variance of soil fertility under the cross-scale influences from island area and DTI, while H’ and Sl didn’t involve cross-scale influences.

Establishing archipelagic landscape ecological network with full connectivity at dual spatial scales

An archipelagic landscape ecological network (ALEN) is important for optimizing the bird migration route and providing reference for island biodiversity maintenance. The ALEN with full connectivity at dual spatial scales was established in this study. Ecological nodes and routes at archipelago scale, as well as ecological sources and corridors at island scale, were identified to constitute the ALEN based on the habitat suitability and integrating the approaches of Euclidean distance and Least cost distance. Then, the landscape structures of the ALEN were analyzed and the optimization measures were proposed to improve the habitat quality and network connectivity. Miaodao Archipelago, an important and typical archipelago in North China, was selected as the study area. Results indicated that the ALEN was composed of 32 nodes and 81 routes at archipelago scale, and 42 sources and 76 corridors at island scale. At archipelago scale, the ecological efficiency of the ALEN was determined by the landscape resistance and position of different islands, and the landscape structure optimization should focus on the islands that involved the indispensable routes. At island scale, the number and spatial distribution of the sources, as well as the landscape structure of the corridors, contributed the most to the ecological efficiency. More ecological sources with uniform distribution should be added, and the corridor width of 50 m was practical to implement the ALEN. The ALEN realized the full connectivity, that is, the bird species could flow (flight or walk) all over the nodes and sources along the routes and corridors across the dual spatial scales, and the balance of efficiency and cost was achieved. The ALEN could be widely applied in different archipelagos with distinct ecological functions and external disturbances.

Spatial pattern of plant diversity in a group of uninhabited islands from the perspectives of island and site scales

Uninhabited islands are important for providing isolated habitats for unique biological resources, and revealing the spatial pattern of plant diversity is of great significance for the island biodiversity conservation. A total of 15 uninhabited islands in Miaodao Archipelago, a group of typical uninhabited islands in North China, were selected as the study area. The multiple gradients at island and site scales were identified and quantified based on field investigation and remote sensing methods, and seven “from macro to micro” aspects, including morphology, proximity, landscape, terrain, atmosphere, soil, and vegetation, were selected to cover all aspects of factors influencing the plant diversity. Then, the single and comprehensive effects of the multiple gradients on the spatial pattern of plant diversity at the dual scales were analyzed using methods of regression analysis and canonical correspondence analysis ordination. Results indicated that 130 plant species were recorded. The species accumulation curves proved the sufficiency of the numbers of sampling sites and islands to represent the overall characteristics of plant diversity. The species composition on the uninhabited islands possessed common characteristics with the neighboring inhabited islands and mainland, meanwhile, showed unique features on the dominant species. The α diversity showed distinct spatial heterogeneities at the dual scales; the β diversity indicated the great difference of species composition within an island and among different islands. At island scale, island area, vegetation condition, and terrain complexity contributed the most to the spatial pattern of plant diversity. At site scale, biodiversity indices changed irregularly along the multiple gradient factors, yet all aspects of gradients showed significant effects on the species composition and distribution. The island area played a fundamental role in determining the α diversity at island scale and generating the β diversity within an island, however, was not significantly correlated with the diversity at site scale.

Archipelagic landscape patterns and their ecological effects in multiple scales

An archipelago is a unique geographic complex with distinct vulnerability to disturbances in coastal areas. The natural features, increasing human activities and their spatial heterogeneities in the archipelago result in complex landscape patterns and ecological effects, which makes the archipelago natural laboratory for landscape ecology study in multiple scales. The particular spatial scales of landscape, island and grid were followed to reveal the comprehensive status, influencing factors and ecological effects of archipelagic landscape patterns, and the Miaodao Archipelago in North China was selected as the study area. Landscape pattern indices (LPIs) in different scales were analysed based on field investigation and geographic information system. Ecological response indicators (ERIs) responding to archipelagic landscape patterns were identified and the relationships between LPIs and ERIs, including land surface temperature (LST), net primary productivity (NPP), plant diversity and soil property, were discussed. Results indicated that plantation, grassland and building land occupied the largest areas in the landscape scale and ERIs significantly differed among different landscape types. In the island scale, some of LPIs regularly changed with the changes in island area, distance to the mainland, population and GDP, yet ERIs were generally insensitive to landscape pattern. In the grid scale, LPIs showed distinct spatial heterogeneities and were affected by altitude and slope; LST, NPP and soil fertility were affected by landscape types, fragmentation, edge effect and shape complexity, whereas plant diversity and soil moisture were mainly influenced by landscape types. The landscape patterns exhibited specific characteristics in different scales, and their ecological effects were closely related to the scales. Island area, distance to the mainland, terrain and human activity were fundamental, the most relevant, limiting and main driving factors of archipelagic landscape patterns, respectively.

Multiple gradient effects on spatial distribution of island soil microbial biomass

Soil microbial biomass (SMB) rapidly responds to the environment and can function as an important indicator for monitoring archipelago ecological vulnerability. An archipelago is featured by distinct and unique gradients between and within islands. The multiple gradient effects on the island ecosystem are worth exploring. We established a multiple gradient system comprising natural, human, and ecological gradients in island and site scales. The natural gradients consist of island area, shape, and distance to mainland in island scale, and terrain and distance to shoreline in site scale; the human gradients include population and exploitation in island scale, and distance to hardened ground in site scale; and the ecological gradients are composed of community type, biomass, biodiversity, and soil physical-chemical properties in site scale. SMB, including SMB carbon (SMBC), SMB nitrogen (SMBN), and SMB phosphorus (SMBP), was used to verify the multiple gradient effects on the island ecosystem, and the northern Miaodao Archipelago in North China was selected as the study area. Results revealed that SMB exhibited distinct spatial heterogeneities. SMBC was sensitive to the natural and human gradients in both scales; SMBN was influenced by parts of natural, human, and ecological gradients in both scales; and SMBP did not show regular changes along the gradients in island scale, yet responded sensitively to the ecological gradients in site scale. The multiple gradient system is unique and fundamental in the spatial heterogeneities of the island ecosystem, and fully revealing the multiple gradient effects is essential for reasonable island conservation and exploitation.

Evaluation on island ecological vulnerability and its spatial heterogeneity

The evaluation on island ecological vulnerability (IEV) can help reveal the comprehensive characteristics of the island ecosystem and provide reference for controlling human activities on islands. An IEV evaluation model which reflects the land–sea dual features, natural and anthropogenic attributes, and spatial heterogeneity of the island ecosystem was established, and the southern islands of Miaodao Archipelago in North China were taken as the study area. The IEV, its spatial heterogeneity, and its sensitivities to the evaluation elements were analyzed. Results indicated that the IEV was in status of mild vulnerability in the archipelago scale, and population pressure, ecosystem productivity, environmental quality, landscape pattern, and economic development were the sensitive elements. The IEV showed significant spatial heterogeneities both in land and surrounding waters sub-ecosystems. Construction scale control, optimization of development allocation, improvement of exploitation methods, and reasonable ecological construction are important measures to control the IEV.