平行岭谷区都市城郊耕地景观演变案例研究——以重庆市沙坪坝区为例

URBAN AND PERI-URBAN FARMLAND LANDSCAPE EVOLUTION IN PARALLELED RIDGE VALLEY AREA——A CASE STUDY OF SHAPINGBA DISTRICT IN CHONGQING

为研究都市城郊耕地景观的演变历程,总结耕地景观演变模式进而为未来研究区的农业资源合理利用和优化调控提供可借鉴性措施,以重庆市沙坪坝区为例,按其地貌特征从东至西划分为东部丘陵A区、岩溶低山B区、中部浅丘C区、西部岩溶低山D区4个区域,以1979年的MSS影像、1988、1995、2001、2007和2010年5个时期的TM影像为基本数据源,采用景观指数和定量表征指标,分析了沙坪坝区耕地景观空间格局演变、空间分布变化幅度及其种植结构引起的耕地景观功能变化。结果表明:A、B、C、D 4区耕地平均斑块面积在1979～2010年有了较大程度的减小,相应的斑块数目有了显著的增加,斑块密度呈现逐步增加的趋势,多样性指数和均匀度指数除了A区在逐步减小外,其他3区均呈增大趋势,耕地景观总体的破碎化程度增加了。2001年以前,除了A区快速减少外,各区耕地面积相对稳定;2001年为界限至今,A、C两区耕地演变属于快速消退型,B、D区则属于逐渐消退型。从2003年到2007年研究区种植作物类型及各区功能定位有所变化,研究区正处于从传统都市城郊农业向现代都市农业的转变中。研究区耕地景观从东部主城核心区到西部缙云山区,呈现跳跃突变式演变的特殊模式。

As one of the main urban area of Chongqing, land use pattern of Shapingba district is strongly changed from the east to the west with the rapid development of social economy in recent years. The aim of this paper is to study the evolution process of farmland landscape in urban and suburban area, summarize the farmland landscape evolution model, and then provide reference measures for the rational utilization of agricultural resources of the study areas in future. Here Shapingba District is took as the study area, and it can be divided into four regions according to its morphologic characteristics：eastern hills as A area, karst low mountains as B area, central shallow hill as C area, west karst low mountains as D area. Taking MSS images in 1978 and the TM images of 1988, 1995, 2001,2007,2010 as the basic data source, we obtained land cover spatial data sets in six phase by interpreting MSS images of the 1978 and five phase TM images of 1988, 1995, 2001,2007,2010 in the Shapingba District. By calculating landscape structure index change, spatial variation amplitudes,we analyzed the spatial pattern evolution of farmland landscape, the amplitude evolution of spatial distribution and functional changes of farmland landscape caused by planting structure in the study area. The results showed that the average patch area of farmland in A,B, C,D area decreased at a large extent during 1979--2010, relavant patch numbers increased significantly, patch density was on gradually increasing trend, the diversity index and evenness index of the other three districts were gradually increasing except zone A which was gradually reducing, and the overall fragmentation degree of farmland landscape enhanced. We took year 2001 as boundary, during 1979--2001, the district arable land was relatively stable in addition to the Zone A which decreased rapidly; and then during 2001--2010 the evolution of arable land in A, C two areas belonged to a rapidly subsided type, the B, D areas belonged to a gradually subside type. From year 2003 to 2007, the growing crop types and functional orientation of every area changed obvious in the study area, at the same time, the study area was in the process of the transition from traditional urban agriculture to modern urban agriculture. From the core area of eastern main city to the western area in Jinyun Mountain, farmland landscape of the study area appeared a special mode of jump mutation-evolving. Area A had almost no cultivated land existing; developing tourism was the main task in area B （we can take the farmland landscape into tourism） ~ the farmland landscape in area C was broad, with urbanization and industrial park promoting, at the same time agricultural landscape should also be reasonable reserved; ecological environment in area D preservation was better （we can increase investment of science and technology and develop the characteristic type of compound ecological efficient suburban agriculture）.