| In this paper,the island of Dongtou District is taken as the research object,based on landscape ecology and 3S technology.To extract the vegetation type of 2014 aerial images.The landscape vegetation index is used to analyze the vegetation landscape of Dongtou Island.Discussing the relationship between the number of vegetation types and the area of the island.To explore the pattern characteristics of vegetation landscapes under terrain and human disturbance factors.At the same time,extract the main vegetation types of Landsat images from 1999,2007 and 2017.The spatial-temporal evolution characteristics of landscape pattern were analyzed from landscape pattern index and transfer matrix.And the change of vegetation landscape under the influence of human activities was discussed.The main results of the paper are as follow:(1)The largest area of vegetation type in Dongtou Island is the broad-leaved forest landscape.The other landscape types are grass,herbaceous vegetation,shrub,coniferous forest,bamboo forest,marsh and aquatic vegetation,and woody vegetation.There is a certain area effect between the island vegetation landscape type and the island area.In general,the number of island vegetation landscape types increases with the increase of the island area.That is,the larger the island,the more abundant vegetation landscape types.(2)Superimpose elevation,slope and aspect grading data with vegetation type extraction data to study the topographic effects of vegetation landscape pattern.It was concluded that the dominant range of coniferous forests is in the elevation of 50-350 m,slope of 15°-60°,northwest and north.The dominant range of broad-leaved forests is in the elevation of 50-390 m,slope of 15°-60°,north,northeast,east and northwest.The dominant range of shrubs is in the elevation of 50-200 m,slope of 15°-75°,northeast and east.The advantage range of the grass is in the elevation of 50-390 m,slope of 15°-75°,east and southwest.The marshland and aquatic vegetation are limited by the plant's own characteristics and growth environment,which grow in the shallow water zone around the elevation of 0 m.The dominant ranges of herbaceous planting vegetation and woody planting vegetation are in the elevation of 0-50 m,slope of 0°-15 °,southeast and south.The dominated range of the non-vegetation area is in the elevation of 0-50 m and 200-390 m,slope of 0°-15° and 45°-75°,flat and west.(3)Due to the influence of human disturbance,the distribution of vegetation landscape is relatively regular.The uninhabited islands are highly inlaid with shrubs and tussock vegetation,resulting in a high degree of fragmentation of landscapes and plaque shapes of uninhabited islands.Compared with the resident's island,the uninhabited islands are more complex.The connectivity between patches,and the diversity of landscape is low.There are residents' islands in contrast.The vegetation coverage rate can reflect the degree of human development.The coverage of islands in Dongtou District is 57.96%.Dongtou Island,Zhuangyuan Island and Lingkun Island are most heavily affected by humans.(4)Use the transfer matrix method to analyze the change of vegetation landscape from 1999 to 2017 in Dongtou Island.During this period,the arbor and non-vegetationincreased,but shrubs and grasses decreased in Dongtou Island.Arbor and non-vegetation are relatively stable landscapes,and the maintenance rate is over 70%.Shrubs are the lowest in the landscape type,only accounting for 4.29%,which are easy to transform into arbors,grasses and non-vegetated.(5)In 1999-2017,the total vegetation area did not continue to decline,but the vegetation coverage rate,vegetation cover structure index and natural index all showed a downward trend.The data shows that although the absolute area of vegetation in Dongtou Island do not continue to decrease.But it doesn't mean the human disturbance of the island ecosystem decrease. |
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