| Land resources are basis for the survival and development of human society.However,in recent years,the ecological risk assessment of land-use landscapes has become a hot issue in global environmental change research,with the continuous acceleration of the urbanization process,the loss of cultivated land and the increasingly serious environmental problems.Scale is one of the cores of landscape ecology research,the granularity of which reasonable determined is the key to the process of landscape pattern change research and landscape ecological risk assessment.Hence,the present research is focused on the granularity effect of landscape index at the county scale and appropriate granularity range of landscape index which is of great significance and reference value to the analysis of landscape pattern changes and improving the accuracy of land use landscape ecological risk assessment.Therefore,based on the geographic and national conditions data of Susong County in 2015 and 2017.This paper,First used the landscape distribution map of Susong County in 2017 as the data source,and analyzed granularity effect of each landscape index in the granularity range of 20~500 m from the two levels of type and landscape.The landscape index inflection point method was used to determine the appropriate granularity range.The fitting function was used to reveal the granularity characteristics of different landscape pattern indexes.The appropriate research granularity was determined by combined with the precision evaluation model of landscape area loss;Secondly,based on the appropriate granularity value,the relevant landscape indexes were selected from three aspects of landscape area and structure,shape,and diversity to study the spatial-temporal changes of land-use landscape patterns.Finally,the ecological risk community was divided,and landscape index such as landscape fragmentation,landscape separation,and landscape sub-dimension were selected to construct the landscape ecological risk assessment model which analyzed the spatial-temporal changes of land use landscape ecological risks and human disturbance activities in Susong County from 2015 to 2017.On this basis,we put forward suggestions and countermeasures for land resource management in different risk areas.The main conclusions drawn are as follows:(1)It was founded that the landscape index had a certain spatial granularity effect at the type level and the landscape level and most of which were highly predictable.However,landscape total area index,average area fractal dimension,average shape index,Simpson diversity index,Simpson evenness index were not sensitive responded to spatial granularity.The granularity effect curve of the landscape index could be divided into four types: monotonically decreasing,monotonically increasing,no change,and complex change and their inflection points were mainly concentrated at 70 and 200 m.At the landscape level,the function types of the landscape index granularity effect curve fitting were mainly power functions and the degree of fitted with good fitness.(2)The appropriate granularity for studying landscape pattern changes in Susong County was determined to be 100 ~ 110 m and the optimal grain size value was 100 m by combined with the landscape index inflection point method and landscape area loss evaluation method.(3)From 2015 to 2017,the dynamic changes of the land use landscape pattern was tended to be unstable in the study area.It was found that the most decreased area was forest land which reduced 969 hm2,the most increased area was construction land which increased 1084 hm2.The fragmentation of the overall landscape was increasing,the shape of the landscape was becoming more and more complex,and the degree of diversity and uniformity was increasing.(4)The distribution of landscape ecological risk levels in Susong County was distributed in a step-like manner which was obviously related to the local geomorphology features and economic development.The ecological risk levels of mineral resource areas,fish and rice towns,transportation hub towns,agricultural areas,and mountain tourist areas were arranged in order from high to low.In the northwest,landscape fragmentation,landscape separation,landscape fractional dimension,the level of landscape diversity and landscape ecological risks were all lower.In the central and southeast,landscape fragmentation,landscape separation,and landscape sub-dimension were higher which shows that the landscape distribution structure was more complicated,and the landscape ecological risk was higher.(5)From 2015 to 2017,the degree of landscape ecological risk in Susong County increased,and the ecological risk level was transformed from a lower level to an adjacent higher level which showed that the low ecological risk areas,lower ecological risk areas,and medium ecological risk areas were decreaseing,while the areas of higher ecological risk areas and high ecological risk areas were increasing... |
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