庙岛群岛北五岛景观格局特征及其生态效应

海岛由于自然特征的空间差异、人类活动的日益增强以及生态系统的脆弱性,其景观格局空间分异性明显且生态效应趋于复杂。以庙岛群岛北五岛为研究区,基于现场调查和3S技术,从景观尺度、海岛尺度和区块尺度分析海岛景观格局空间特征,进而探讨景观格局与净初级生产力(NPP)、植物多样性和土壤性质的关系。结果显示:(1)不同尺度景观格局均表现出了空间差异。景观尺度上,针叶林、阔叶林和草地3类植被景观面积最大,斑块密度、边缘密度和平均形状指数总体较高,建筑用地也具有较大规模,其斑块密度较高,平均形状指数处于最低值,裸地也具有一定规模,其各项景观指标处于中间位置;海岛尺度上,随着海岛面积、人口和GDP的增加,斑块密度和人为干扰指数均明显增大;区块尺度上,斑块密度、边缘密度和平均形状指数与海拔呈显著正相关,人为干扰指数与海拔和坡度均呈显著负相关。海岛面积、地形和人类活动分别是北五岛景观格局的基本因子、重要限制因子和直接驱动因子。(2)海岛景观格局的生态效应与尺度密切相关。景观尺度上,各项生态效应指标在不同景观类型上均具有显著差异,海岛尺度上的生态效应指标对景观格局的响应不甚灵敏;区块尺度上,生态效应指标与景观格局指数表现出了显著的简单相关性和偏相关性,但二者结果具有差异。NPP和土壤水分主要受到景观类型和植被生长状况的影响,多样性和土壤养分同时受到景观类型和景观格局破碎度、边缘效应的影响,人为活动强度的增大地带来了各项生态效应指标的降低。控制建设规模、优化景观布局与改进开发利用方式是维系海岛生态系统稳定性的重要措施。

Landscape pattern characteristics and ecological effects on five northern islands of Miaodao Archipelago

Landscape pattern is the outcome of comprehensive effects of natural and human factors on geographical space, and has a significant impact on the structure, function, and process of ecosystems. An archipelago is an aggregation of multiple neighboring islands, and there are significant differences in the basic features such as areas, shapes, and terrain conditions between and within the islands in an archipelago. Meanwhile, human activities, including urban and rural construction, plantations, and transportation, as well as the vulnerability of island ecosystems, are spatially heterogeneous on an archipelago, which make the landscape types more diversified, resulting in more differential landscape patterns and complex ecological effects. In this study, five northern islands of the Miaodao Archipelago were used as study areas, which are the typical islands in North China, located north of the Shandong Peninsula, at the juncture of the Yellow and Bohai Seas. The driving factors of landscape pattern here are highly complicated. Based on field investigations, 3S technology methods were adopted. Patch density (PD), edge density (ED), mean shape index (MSI), and human interference index (HII) were used as the landscape pattern indices. The landscape patterns were analyzed in landscape, island, and grid scales, respectively. Then, the relationships between landscape pattern and ecological effect indicators, including net primary productivity (NPP), plant diversity, and soil properties, were examined. The results revealed that the landscape patterns showed obvious spatial heterogeneity in different scales. In the landscape scale, coniferous forest, broad-leaf forest, and grassland constituted vegetation landscape, which occupied the largest proportion of island landscape, and their PD, ED, and MSI were generally higher. Construction land also had a larger area and its PD was higher but its MSI was minimal; the area of bare land was smaller than those of the above-mentioned types with median landscape indices; the areas of the other landscape types were < 100 hm². In the island scale, both PD and HII increased with increases in island area, population, and GDP. In the grid scale, PD, ED, and MSI had significant positive relationships with altitude, whereas HII had significant negative relationships with altitude and slope. Different landscape pattern indices were also related to each other, and there were significant positive correlations among PD, ED, and MSI. HII had significant negative correlations with PD and ED. Island area, terrain, and human activities were the fundamental, limiting, and direct driving factors of the landscape patterns, respectively. The ecological effects of landscape pattern were closely related to the scale selected. In the landscape scale, all the ecological effect indicators showed significant differences in different landscape types. In the island scale, the responses of ecological effect indicators to landscape pattern were insensitive. In the grid scale, ecological effect indicators and landscape pattern indices had significant simple and partial correlations, yet the results of simple and partial correlations showed differences. NPP and soil moisture content were mainly influenced by landscape types and vegetation status. Biodiversity and soil fertility were influenced by landscape types, and the fragmentation and edge effect of landscape pattern. Increased intensity of human activity has led to a decrease in each ecological effect indicator. Construction scale control, optimization of landscape allocation, and improvement of utilization methods are important measures to maintain the stability of island ecosystems.