Land Use Change And Its Landscape Ecological Risk Assessment In Jiaozhou Bay Coastal Zone Based On Small Watershed Scale

Coastal zone of Jiaozhou Bay was selected as the study area.The data of 30 m-resolution DEM and ETM+/OLI images in 2000 and 2016 were collected.Land use information was obtained based on ArcGIS and ENVI technology.The study area was divided into several small watersheds.The landscape pattern index,ecological risk grade atlases and spatial patterns were generated using the Fragstats landscape analysis method,Geoda and GS+ integrated technology.Based on land use change model,cluster analysis and landscape ecological risk assessment system,the changes of land use and its influencing factors in small watershed scale were analyzed,and the changes of ecological risk,autocorrelation and heterogeneity were also discussed.The results revealed that:(1)During 2000-2016,the land use structure and area of small watersheds changed obviously.For example,construction land increased and became the main type.Salt pans,cultivated land and aquaculture ponds decreased significantly.The dynamic degree among small watersheds were different.In the small watershed 1-4(Southwest section),cultivated land,aquaculture ponds changed negatively.Forest and grassland and construction land changed positively.In the small watershed 5-10(Central section),forest and grassland,cultivated land and salt pans changed negatively.Construction land changed positively.In the small watershed 11-13(Central section),cultivated land,aquaculture ponds changed negatively.Salt pans and construction land changed positively.In the small watershed 14(Southeast section),aquaculture ponds,tidal flats,construction land and waters changed negatively.Forest and grassland,salt pans changed positively.In the comprehensive dynamic degree of land use,among the small watershed 1 to 14,the small watershed 9 had the highest annual change rate and the greatest degree of change,the change in the small watershed 14 was the minimum.The main reason was the irrational land use pattern caused by the expansion of construction land and the development of regional economy.(2)At the same point of time,the degree of order among different small watersheds was obviously different.The different proportion of multiple land use types in the small watershed leaded to different degree of order.The small watershed 2 and 14 were in decline;while others small watersheds were in development.The small watersheds were classified into four categories based on the information entropy and comprehensive index of land use.The order of land use degree and single status were: ?>?>?>?.Except for the small watershed 2 and 14 in class II,others small watersheds were in development period and tended to be single.The small watershed 9 in class IV had the highest level of the development and single.The urbanization level and the implementation of economic policy had a significant impact on the degree of simplification and the development of small watershed.In the four types of small watersheds,land type conversion was the most frequent from other land types to construction land.(3)The construction land was expanded and stable.The fragmentation degree of cultivated land and salt pans increased.The parts of the forest and grassland were all transferred out.And the patches expanded in the fixed area.Aquaculture ponds and tidal flats were dispersed;and the stability was reduced.In 2000 and 2016,the study area was mainly covered by the lowest ecological risk areas which accounted for 79.63% and 79.35% of the total area,respectively.In 2000,the highest ecological risk areas were distributed in the offshore area;and the higher risk areas were semi circle in the periphery of the highest ecological risk areas.In 2016,there were only a few scattered spots of the highest ecological risk area.The higher ecological risk area was distributed along the northern coastal area of the Jiaozhou Bay.Most of the middle ecological risk areas were distributed on the periphery of the higher ecological risk areas.The ecological risk area in the watershed changed significantly.During 2000-2016,the distribution of higher ecological risk area was reduced from the small watershed 3-10 and 12 to the small watershed 3,6,7,9,10 and 12.The highest ecological risk area was reduced from the small watershed 3,4,6-10,12 to the small watershed 3,6,7,9.(4)Due to the difference of the ecological risk grade,the proportion of each class and the trend of change were different.The types of dominant land use were also different.The Moran's I index decreased;spatial autocorrelation and spatial homoplasy also decreased.The ecological risk index of the study area was dominated by high-high concentration(H-H)and low-low concentration(L-L)types.The H-H type was mainly distributed in the offshore area of the study area and the Jihongtan Reservoir area.The L-L type from small watershed 2,4,5,10,13 and 14 gathered in the east and south of study regions.During 2000-2016,the value of the block gold/base increased,so the spatial differentiation effects of the nonstructural factors on the ecological risk index increased in the study area.The transformation of risk areas at different levels was mainly concentrated in the small watershed of 4-10 and 12 in coastal areas.In the other areas,the transition of risk grade was mainly in the middle ecological risk areas,the lowest ecological risk areas and the lower ecological risk areas;it was dispersively distributed.There was no conversion from the lowest to higher ecological risk area.There was no conversion from the lowest to the highest ecological risk area.There was also no conversion from higher to the highest ecological risk area.Conversion occured between the other ecological risk areas.