Impacts of the Land Surface Slope on Forest Spatial Distributions

Forest is the largest terrestrial ecosystem on the earth. Quantitative evaluation of the impacts of the land surface slope on forest spatial distributions is of great significance for a deeper understanding of functions and stability of forest ecosystem, scientific planning and rational management of forest resources. The superposition analysis of map of vegetation and digital elevation model (DEM) is an effective method to study impacts of the land surface slope on forest spatial distributions. In the past time, the data of land surface slope was mainly obtained by field measurement which had some problems of time-consuming, labor-intensive and high investigation cost. With the development of space technology, DEM data can be used to obtain land surface slope data rapidly and efficiently which has been widely used in digital forestry construction. However, studies on the influence of land surface slope on forest spatial distribution by using DEM data are rare at home and abroad. Dali City of Yunnan Province was selected as the research area in this study. The contour line vector is used to establish DEM of this area, then collect the slope data and divide the slope grades into five groups: flat slopegentle slopemoderate slopesteep slope and sharp slope. Supervised classification and visual interpretation were executed to interpret and classify the map of vegetation of Dali. By putting map of forest distribution and DEM togetherthe relationship between forest distribution and slope was analyzed and the trend of forest spatial distribution was found out. The results showed that Dali city is relatively flat and the terrain is complex and diverse. The woodland has a large area distribution in Dali City, which is related to the monsoon climate of the subtropical plateau in Dali. The shrub forests were mainly distributed on moderate slope and steep slope, and the coniferous forests were mainly distributed on gentle slope and moderate slope. As the slope changes, the distribution of shrubberies increases and decreases sharply, indicating that shrubberies are highly dependent on slope. Coniferous forests have a large area distribution at each grade, indicating that they are less dependent on slope. In general, with the increase of slope, both forest types showed a trend of increasing first and then decreasing, indicating that the surface slope has an impact on the spatial distribution of forests. This study can offer reference to the rational and scientific management of forest resources.