关键词: 城市化, 农业景观, 破碎化, 生态服务, 西安都市圈

Abstract: Agro-ecosystem has become an integrated crop production system with significant human disturbances. The urban sprawl and the conversion of agricultural types and agricultural landscape pattern driven by rapid urbanization have profoundly impact on ecosystem services which are provided by agro-ecosystem and strongly endanger to the eco-environmental security in cultivated region. Particularly, the fragmentation of agricultural landscape can explain a great part of the losses of ecosystem services in these regions. In recent 14 years, the urbanization level dramatically improved from 34.34% to 46.74% with the immigration of large number of rural population to urban area, the industrial development, the road construction and the built-up area expansion in Xi'an metropolitan zone. The rapid economic development and urbanization result in the huge changes of land use and agricultural structures and the landscape fragmentation, even bring to soil pollution and water resource shortage. Regional ecosystem services are strongly influenced by these processes, especially by the landscape fragmentation. The paper mainly focused on what's the process of agro-ecosystem landscape fragmentation and how's the influences of landscape fragmentation on ecosystem services in Xi'an metropolitan zone. Better understanding of these questions is particularly helpful for improving the awareness of ago-ecosystem services from the view of landscape ecology, and providing the recommendation for government agencies on decision-making of the ecological land conservation, the agricultural development, the regional urbanization and the regional ecological security. Based on the Landsat imageries, land use map and eco-social survey data, the changes of agricultural type and landscape pattern were studied dynamically, and further, the influences of agricultural landscape fragmentation on ecosystem services were analyzed in rapid urbanizing region of Xi'an metropolitan zone from 1988 to 2013 by employing the theories and methods on landscape and ecosystem services. The results showed as follows:(1)With rapid reduction of cultivated land area and the increase of orchard and built-up area, the agricultural landscape fragmentation has been occurred in recent 25 years, the landscape pattern gradually diversified and landscape patch shape were irregular. The patch density, Shannon's diversity index and landscape shape index were increased by 32%, 35% and 30% respectively in recent two and half decades. The dominant degree of cropland was gradually decreased among land types.(2)The expansion of urban built-up area resulting from huge central cities, transportation and tourist attraction construction and the growth of a great number of towns in region which result in the cropland, orchard, forest and grassland decreased and fragmentized are the main driving factor of landscape fragmentation; and the conversion of agricultural types, in which orchard dramatically increased and traditional crop production generally dropped, is the another principal driver factor.(3) Total value of multiple ecosystem services decreases by 1.3%, as the characteristics of the improvement in provision and recreation services and the decrease in life supporting services. The value of ecosystem services is greatly decreased in urban and residential areas where newly expanded from 1988, while it is greatly increased in other areas where newly formed lands like orchard, crop land and urban inner parks.(4)Ecosystem services' value will be improved in the earlier period of the regional central city expansion and the transformation of agricultural types because in that time the cropland landscape fragmentation is dominant. After that, however, the ecological services will be reduced thoroughly by the built-up area expansion network-likely that result from urban overspreading and large number of town's growth, transportation system stretching, tourism resort developing and industrial zone constructing around the whole region in the medium and later period of urbanization, in this time the multiple landscapes will be fragmentized completely and that cause to entire losses of ecosystem services. Therefore, this paper suggests that in the period of the sprawl of entire central cities and the growth of entire towns will cause to dramatically and eventually damage of ecosystem services in an cultivated, huge population density and rapid urbanizing region due to where the ecosystem services tightly depend on agro-ecosystem landscape, and also implies that to implant more large area of orchard, woodland, grassland and water body and to maintain the high degree of the landscape aggregation can improve the regional ecosystem services.

Key words: urbanization, agricultural landscape, fragmentation process, ecosystem services, Xi'an metropolitan zone