西安市城市化对景观格局及生态系统服务价值的影响

我国处于城市化高度发展阶段，截止2018年全国城市化率达到59.58%。城市的快速扩张，显著改变了区域景观格局，深刻影响城市生态系统的供给、调节、文化、支持等服务功能。近30年来，西安市城市用地扩张554.23 km²，基于西安市景观格局变化分析，利用同心缓冲区探讨城乡梯度内景观指数与生态系统服务价值的特征及其相互关系，揭示城市发展对城市生态系统的影响。结果表明，1980-2015年西安市各景观类型面积发生明显变化，耕地、草地面积逐渐减少，建设用地面积波动增加，主要来源于优势景观耕地的转化。景观破碎度最高的区域主要分布在距市中心10 km左右的城乡结合部，斑块密度、边缘密度、景观分割度最高，且随城市扩张，拐点距离逐渐增加。林地和耕地是提供生态系统服务的主要土地类型，西安地区总生态服务价值减少了9.56亿元，耕地减少最多（6.83亿元），沿城乡梯度，总生态系统服务价值均值呈现从市中心到农村递增的趋势，土壤保持的生态服务价值增长最快；沿时间梯度上，生态服务价值均值呈现逐年减少现象；从景观格局对生态服务价值影响分析得知，多样性指数与各类型生态系统服务价值之间存在显著的相关关系，最大斑块指数与不同类型的服务价值呈高度负相关。城市建设使得区域的生态系统服务价值降低，在城市发展中需要科学规划用地、合理布设景观格局，提高生态环境质量，达到城市生态宜居的目的。

Influence of urbanization on landscape pattern and ecosystem service value in Xi'an City

China is in a high stage of urbanization, and the national urbanization rate was 59.58% by 2018. The rapid expansion of the city has significantly changed the regional landscape pattern and the ecological system service functions (i.e. supply, regulation, culture, support services). In the past 30 years, the urban land has expanded by 554.23 km². Based on the analysis of the landscape pattern change of Xi''an, the concentric buffer zone method was used to explore the relationship between landscape index and ecosystem service value in urban-rural gradient. The purpose of this study was to reveal the impact of city development on urban ecosystem. The results showed that the area of landscape types in Xi''an changed remarkable from 1980 to 2015. The area of cultivated land and grassland decreased gradually, and the fluctuation of construction land area increased, which mainly due to the transformation of dominant landscape cultivated land. The area with the highest landscape fragmentation is mainly located in the urban-rural junction, about 10 km away from the city center. This region was characterized by the highest patch density, edge density and landscape segmentation. The variation trend of landscape index showed an inflection point in the 35 years change, and the point distance was gradually increased with the expansion of urban area. Forestland and cultivated land are the main land use types to provide the ecosystem services. The total ecological services value in Xi''an decreased by 956 million yuan, and the cultivated land had the most decreasing of ecological services value compared with other land use types (683 million Yuan). In the spatial scale, the average value of total ecosystem services had an increasing trend along the urban-rural gradient from the city center to the countryside, with fastest increasing rate in soil conservation ecosystem services. In the temporal scale, the average value of ecosystem services decreased year by year. While by analysis the impact of landscape pattern on the value of ecosystem services, it was found that there was a significant correlation between Shannon''s Diversity Index and the value of ecosystem services, and the Largest Patch Index was highly negatively correlated with different types of ecosystem service value. Urban construction reduced the value of regional ecosystem services. In the future city development, it is necessary for us to plan land use and landscape pattern scientifically, so as to improve the quality of ecological environment and achieve the purpose of urban ecological livability.