The Landscape Pattern Characteristics And The Impact Of Landscape Metrics On Grain Size Effect Of The Arid Valley

The arid valley in the Hengduan ranges is located in southeast China.It has special terrain and topography and its ecosystems is fragile.So the valley is the most critical and difficult landscape type in the process of the mountains’ management.However,the researches of the study area has been concentrated in the 1980 s and they were more partial after the 20 th century.Besides the boundaries of the arid valley in the Hengduan ranges has no precise definition over the years.not to mention the study of its landscape pattern.In recent years, the researches of the landscape patterns has a growing tendency to large-scale and quantification.as a primary method of quantitative research,the precision and accuracy of the landscape metrics are restricted by landscape size,thus the impact of landscape metrics on grain size effect become a hot point.Therefore determine the boundaries,compare and analyze its characteristics by different watershed,then choose the proper samples of the area,study the impact of landscape metrics on grain size effect and find the most suitable size of the dry valley landscape to analysis its landscape pattern in landscape level and class level has important significance.It can not only make up the vacancy of the study for impact of landscape metrics on grain size effect but also have important and practical significance to propose environmental protection measures to local conditions for ecological security of study area and its regional environment.Using the software ENVI, ARCGIS,combining vegetation and altitude data in the region,this article extracts boundaries of the arid valley in Hengduan ranges.According to the basic characteristics of the study area as well as their areas,altitude, terrain features,select three representative sample areas:the upper reaches of the Jinsha River, the Yuan River, the Minjiang River,choose 22 Intermittent sizes from30-450 m,then calculate 16 landscape indices in landscape level and 6 landscape indices in class level.Draw graphs about the impact of landscape metrics on grain size effect and use SPSS software to do its curve fitting.After determining the first scale domain of each indices and the most appropriate grain size, intersect them to get the most suitable size for the arid valley in Hengduan ranges.Using this size to grid all basins in study area and calculate,then analysis the characteristics of landscape patterns in landscape level and class level.Here are the results:the total area of the study area is 33391.60km2.The study area has the landscape pattern that the grassland, shrub land is the matrix,the river is the corridor and the other plaques run throughthem.The altitude ranges from 254 to 5707 m,which shows a significant mixed terrain of mountains and valleys. It has a steep topography and largely ranges from 0 to 87.17 °which the mean value is 25.77°.Each aspect of the valley are almost distributed equally,the areas of sunny area is little higher than the shady area.The characteristics have obvious differences between the different watershed of the arid valley and its spatial locations from south to north.The tendency of characteristics of landscape patterns in landscape level and class level for the three sample are similar.the graphs about impact of landscape metrics on grain size effect can be divided into four categories:no law,increasing,decreasing,no change.Most curve fitting of landscape indices are good and have high R2.Compare and analysis the first scale and the appropriate gain size of the landscape indices,it comes to the conclusion that the most appropriate gain size in landscape level and class level of the arid valley in Hengduan ranges is 75 m.Using this size to calculate all the landscape indices in study area,we can see with the basic characteristics changing,the landscape pattern in landscape level exhibits of the arid valley in Hengduan ranges have changed from northwest to southeast too,the value of aggregation for different class are high,but the other indices in class level show a significant difference due to the area of class and degree of human activities.