Urban and peri-urban farmland landscape evolution in paralleled ridge valley area——a case study of shapingba district in chongqing

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).