| Land use system is a unity with both natural and social attributes,which is more and more easily affected by human society.China is a populous country with obvious urban expansion in recent years.Therefore,human society has put forward higher requirements for land resources,and the contradiction between man and land has become increasingly prominent.In addition,in the process of land development,people focus more on how to develop land,but neglecting the maintenance of land quality,problems such as land degradation,waste of land resources and decline of land quality getting worse.Under this background,it is particularly important to ensure land quality and improve land use efficiency,so as to improve the health level of land use system.In this paper,Jiangjin District is taking as the study area,firstly,analyzing the changes of its land use and landscape pattern.On this basis,taking the"pressure-state-response"model(PSR model)as the framework,and constructing the health evaluation index system of land use system,then the comprehensive index model is used to evaluate the land use system health status of Jiangjin District and its three functional zonings respectively,to clarifying the health level of land use system in Jiangjin District and exploring the regional differences of land use status.Secondly,the obstacle degree model is introduced to calculate the obstacle degree of each evaluation index,and the obstacle degree values are sorted to find out the main factors affecting the health of land use system in the study area from 2005 to 2018.Finally,based on the actual situation of land use system,this paper puts forward some countermeasures to improve the health level of land use system in different regions,in order to provide theoretical basis for rational planning and utilization of land resources in Jiangjin District and its functional zoings.The results showed that:(1)The land use system in Jiangjin District has changed significantly,the degree of land use has deepened,and the landscape pattern has changed greatly.Cultivated land and forest land were the main land use types in Jiangjin District.From 2005 to 2018,the cultivated land decreased by 10869.85hm~2,its landscape shape index increased,the aggregation index decreased,the landscape shape became complex and the landscape's heterogeneity increased.The area of construction land increased significantly,with a total increase of 6358.83hm~2in 13 years,its landscape shape index increased and the shape became more complicated.The forest land area increased by 7439.22hm~2,and the patch cohesion index and aggregation index decreased,which indicated that the forest land fragmentation was aggravated and the landscape connectivity was decreased.The water area decreased by 2848.50hm~2,but its landscape connectivity increased.The grassland area has increased slightly,and layout of the grass patches tended to be concentrated.The unused land area decreased by 1227.73hm~2,and its single land use dynamic attitude was the largest.From 2005 to 2018,the land use degree of Jiangjin District decreased first and then increased,and after 2010,the land use degree continued increasing,the comprehensive index of land use degree increased from 263.33 to264.68.(2)There were significant regional differences of land use in the three functional zoings of Jiangjin District.In zone I,the population was growing fast,and the level of economic development was high.The expansion of construction land in zone I was the most obvious,the landscape dominance rising from 2005 to 2018,the landscape shape tended to be complex,the landscape fragmentation was deepened,the connectivity was reduced,the types of land use are getting richer and richer,and the landscape pattern was developing towards homogenization.In zone II,the area of cultivated land accounted for more than 50%.From 2005 to 2018,the area of cultivated land decreased,the area of forest land increased,and the area of construction land increased slightly.The landscape diversity did not improve significantly during the study period.In zone III,the landscape structure remained unchanged from 2005 to 2018,with forest land as the main land type,accounting for more than 70%of the total area,followed by cultivated land.The policy of returning farmland to forest led to the results of landscape becoming fragmented and the shape of landscape becoming irregular.(3)The health level of the land use system in Jiangjin District was poor,and there were obvious differences about the health level of the land use system among the three functional zonings.The land use function and the economic development level were different,so the health level were different,but they were all getting better.The health level of land use system in Jiangjin District and its three functional zonings did not appear"morbid",but the health level of land use system in Jiangjin District was not ideal,and the comprehensive health index was less than 0.5 in the study period,the contradiction between economic development and land use was prominent.In zone I,the level of urbanization and economic development was high,and the land use system was most disturbed by human activities.Although the pressure of land use was gradually increasing in the process of urbanization,the contradiction between supply and demand of economic development and land use system has been alleviated by human society,and the land use system was in good condition,developing towards a healthier direction and reaching a sub-healthy state in 2018.In zone II,the urbanization level was lower,and the economic development speed was slow,the health level of land use system was low,and the comprehensive health indexes were lower than 0.6 from2005 to 2018,the health level of land use system was fluctuating between critical state and unhealthy state.In zone III,eco-tourism was common,and the land use system was in good health,the health level of land use system changed to sub-health state by 2018,and further efforts will be needed to achieve a healthy state.(4)Each evaluation subsystem and specific evaluation indicators had different influences to the health of land use system in different functional zonings,the reduction of obstacle degree of response subsystem played a key role in improving the whole health level of land use system.In zone I,separation index,dominance index and fragmentation index were the main obstacles,the obstacle degree of state subsystem was the highest,which was above 50%and showed an increasing trend,it was the main obstacle to improve the health level of land use system in this area,the obstacle degree of pressure subsystem increased,while the obstacle degree of response subsystem continued decreasing,in the future,the government should pay more attention to improve the health levels of pressure and state subsystems.In zone II,fragmentation index,diversity index and evenness index were the main obstacle factors,and the obstacle degree of state subsystem was on the high side,which has increased continuously since 2010,from 34.91%in 2010 to 71.13%in 2018,the health level of state subsystem should be paid more attention,the obstacle degree of pressure subsystem and response subsystem had decreased.In zone III,ecological elasticity,dominance index and complexity index were the main obstacle factors,compared with zone I and zone II,the obstacle degree of pressure subsystem was the lowest,but the obstacle degree of state subsystem was larger than 50%,which was the biggest obstacle restricting the sustainable utilization of land resources,the obstacle degree of response subsystem was decreasing continuously.In the future,enriching land use types and improving ecological carrying capacity will be the key work for zone III. |
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