Effect of urban expansion on non-agricultural habitats in farmland landscape: A case study of Shenbei New District, Shenyang City, Liaoning Province

Farmland landscape area accounts for 38% of the Earth’s land surface. Farmland landscape is very important for the protection of biological diversity and endangered species. Modern agriculture is characterized by industrialization and high yield, simplifying biodiversity and weakened function of biodiversity protection of farmlands. Non-agricultural habitats in farmlands are natural and semi-natural habitats including grasslands, forests, hedges, country roads, ditches. There are plenty rare species in non-agricultural habitats that are very important for the conservation of biodiversity, landscape structure and agricultural yield. However, severe changes in non-agricultural habitats (including grassland, forests and pools) have led to such lands converting into arable lands. This is the predominant phenomenon in suburban farmlands in China. Thus this paper analyzed the influence of urbanization on non-agricultural habitats by transecting farmland landscapes in Shenbei New District in Shenyang City, Liaoning Province. Firstly, the Shenbei New District was divided into city area, urban fringe area and rural area based on landscape disorder grade. Secondly, ten sampling bands were set up outward from the center of city. Four sampling bands were in city area, four in urban fringe area and two in rural area. Thirdly, the type, patch number and area proportion of non-agricultural habitats across sampling bands were analyzed in GIS. The results showed that non-agricultural habitats gradually increased with increasing distance from city area to urban fringe area and rural area. There was only forest in nearby city farmlands. There were grasslands, forests, pools and patches in rural farmlands. The proportion of patch number of non-agricultural habitats also gradually increased from city area to rural area. The average proportions of patch number were 8.63% in city area, 17.08% in urban fringe area and 22.48% in rural area. However, the proportion of patch area of non-agricultural habitats followed a inversed U-shape pattern of change from city area and urban fringe area to rural area. The maximum proportion of patch area in urban fringe area was 1.93%. The patch density of non-agricultural habitats gradually increased initially, then decreased and finally increased, with the minimum patch density in urban fringe area. Also the largest patch index and aggregation index gradually decreased initially and then increased, with the minimum largest patch index and aggregation index in urban fringe area. Landscape shape index and diversity index gradually increased initially and then decreased, with the maximum landscape shape index and diversity index in urban fringe area. In general, non-agricultural habitats in city area had single type, low proportion of patch number, larger patch and the regular shape drastically affected by urbanization. It was falsely apparent that the proportion of patch area, landscape shape index and diversity index in urban fringe area were highest due to disturbance of farmlands by urban construction. However, it was lower in patch density, largest patch index and aggregation index. Non-agricultural habitats in rural area had diverse types, high proportion of patch number and high landscape heterogeneity. The result of this research was a significant reference for increasing biodiversity and heterogeneity of non-agricultural habitats for improved health of farmland ecosystems.