Spatial Responses of Vegetation-Soil System to Complex Factors in a Sandy-Rocky Island Chain

The vegetation-soil system is fundamental to island ecosystem and changes considerably across sandy and rocky islands due to different natural and anthropogenic factors. An island chain, which is characterized by the coexistence of sandy and rocky islands, the connection of the islands by bridges, and complex influencing factors, was used as the study area. The vegetation-soil system was represented using different indicators and three newly-proposed indices, namely, vegetation health index (VHI), soil health index (SHI), and vegetation-soil system health index (VSSHI). The complex factors were identified in aspects of island basic factors, landscape pattern, terrain condition, and ecological indices. Then, the spatial responses of the system to the factors were analyzed at island and site scales. Results indicated that the vegetation-soil system showed similar and different responses to the complex factors across the dual scales. The similarity was represented by the higher sensitivities of VHI and VSSHI compared with that of SHI at both scales, and the difference mainly indicated that the influences of landscape pattern factors distinctly decreased along the scales from island to site. Island area, sea reclamation proportion, vegetation proportion, and natural ecosystem damaged index were the most important factors at island scale, while the ecological indices showed the highest influences at site scale. The study revealed the spatial characteristics of the vegetation-soil system across different types of islands, clarified the spatial responses of the system to complex factors at the dual scales, and identified the main influencing factors of the system.

Long-Term Changes in the Unique and Largest Seagrass Meadows in the Bohai Sea (China) Using Satellite (1974–2019) and Sonar Data: Implication for Conservation and Restorationc

Seagrass meadows play critical roles in supporting a high level of biodiversity but are continuously threatened by human activities, such as sea reclamation. In this study, we reported on a large seagrass (Zostera marina L.) meadow in Caofeidian shoal harbor in the Bohai Sea of northern China. We evaluated the environmental impact of sea reclamation activities using Landsat imagery (1974–2019) by mapping seagrass meadow distribution changes. ISODATA was adopted for the unsupervised classification and mapping of seagrass beds. The error matrix developed using the in situ data obtained from acoustic surveys for Landsat 8OLI image classification was 87.20% accurate. The maps showed rapidly increasing changes in seagrass meadows as the amount of reclaimed land increased. Some seagrass meadows experienced large-scale changes, and sea reclamation has been suggested as the main factor responsible for habitat loss, which results from physical damage, excessive sedimentation, and increased turbidity caused by reclamation. In addition, habitat degradation may have resulted from three storm surges induced by typhoons in 1992–1998. Fortunately, land reclamation, forming an artificial “longshore bar”, buffers seagrass meadows from wave actions, providing relatively sheltered conditions, which has allowed a large habitat increase since 2012. These were the largest eelgrass meadows (3,217.32 ha), with a peripheral area of ~100 km2, in the Bohai Sea of northern China in 2019. However, the existing largest eelgrass beds in China are threatened by trawling, clam harvesting (especially clam sucking), channel dredging, and culture pond construction. Our work will help coastal managers monitor the environmental impacts of reclamation activities on seagrass meadows on a large spatio-temporal scale and will also provide information for seagrass restoration using artificial “longshore bars”.

Characteristics and Mechanism of the Environmental Capacity Changes in Haizhou Bay, Northern Jiangsu, China from 2006 to 2016

Haizhou Bay is an open bay located in northern Jiangsu Province, China. This study analyzes the changes in the coastline, coastal development, and water quality of Haizhou Bay between 2006 and 2016. The box model method and numerical simulation are adopted to calculate the environmental capacities of Haizhou Bay in 2006 and 2016, analyze changes to environmental capacity features, and assess the influencing factors over this period. The scenario analysis method is used to discuss the influencing mechanism and degree of influence of factors (e.g., the water quality difference inside and outside the bay, and sea reclamation) on the environmental capacity and calculate the contribution of each influencing factor. The changes in terrain triggered by sea reclamation and water quality from 2006 to 2016 reduced the total environmental capacity of Haizhou Bay, with an influencing ratio of 0.198:0.802. In other words, poorer water quality inside the bay reduces the environmental capacity by a degree of 4.05 times that of sea reclamation. This study can offer guidance on related future research aiming to protect the marine environment of Haizhou Bay and control the total amount of pollutants discharged into the sea.

Safety Management in Sea Reclamation Construction: A Case Study of Sanya Airport, China

Urbanization has increased the burden on land resources. Artificial island construction has been proven as an effective method for addressing these land resource problems; however, few studies have been conducted on the safety of sea reclamation construction. This paper proposes a systemic approach to the complete safety management process in sea reclamation engineering, including safety system design, analysis, control, and assessment, using the Sanya Sea Reclamation Airport, Hainan Province, China, as a case study. A total of 145 steel cylinders must be vibrated and sunk into the seafloor to create a 9 km quay wall. Owing to their large size, the steel cylinders have been divided into different segments, and an assembly jig is employed to ensure a safe production process. Considering the hazardous working environment in sea reclamation construction, a numerical analysis is conducted to investigate the safe repertory of these steel cylinders and verify the reliability of the selected scheme for their transportation. Finally, control measures are adopted to ensure a safe vibration and sinking procedure for the steel cylinders. The proposed approach could be used to provide safety management guidelines for artificial island engineering and construction.