Analysis on land use pattern changes in Harbinbased on terrain gradient

Abstract: Rapid land use pattern change has taken place in Songhua River basin of old industry base in Northeast Region of China over the past decades in Harbin Province. To explore evolution process of land use pattern on terrain gradient, data interpreted with RS and GIS technology from remote sensing images (Landsat TM/ETM+) were collected in 1989, 1995, 2001 and 2007, respectively. Based on the geo-information image analysis theory, the rules of land use spatial pattern changes and structural characteristics were analyzed, reasons and mechanisms of land use change were disclosed. Afterwards, terrain gradient-based spatial differentiation and spatial-temporal evolution process of land usage were studied further based on DEM (digital elevation model). The results showed during the past 18 years, cropland and forestland were the dominant land use types, areas of cropland and unused land were decreased constantly, the average area of cropland patch were decreased from 20.96 km2 to 3.92 km2,while the average area of unused land patch was decreased from 2.87 km2 to 0.09 km2, which showed that the fragmentation degree of both cropland and unused land aggravated seriously, and at the same time, the estuarine and coastal wetlands were the main transformation trace to cropland for unused land. Areas of cultivated land were increased constantly with an unbalanced station. Compared to the increased land areas of cultivated land, cropland acted as the main source for transforming to the other land use types, the fragmentation of forestland was increased from 0.117 to 0.532 piece /km2, which showed that the fragmentation degree became more and more serious. When the terrain niche grade was 2, the distribution index of the Pre-change Model and the Continuous Change Model reached their top values. However the Stable Model and the Repetitive Change Model became the largest when the terrain niche grade changed to 1. Afterwards, distribution index of these models was decreased with the increase of the terrain niche grade. Distribution of the Intermediate Transition Model matched with the certain curve. This study provides a scientific basis for planning and using land properly in the process of urbanization.