| The Loess Plateau, the birthplace of Chinese farming culture, is located in the upper and middle reaches of the Yellow River, the center of China. It has an important strategic position in Chinese ecological environment construction and economic development. A small watershed is the basic research unit for comprehensive soil erosion control and socio-economic on the Loess Plateau. It has important theoretical and practical significance to study the changes of land use/cover pattern at a small watershed scale on the Loess Plateau.Irrational land use accelerated soil erosion on the Loess Plateau, and has resulted in land degradation and poverty life of farmers. Therefore, it is necessary to study land use change and their driving forces, to put forward reasonable and sustainable land use optimization program, and to carry out ecological function zoning. The above work is an important way for comprehensive soil erosion control, improving the eco-environment, developing ecological agriculture, and achieving good circulation of eco-environment and sustainable development of agriculture.In this dissertation, based on the theories and methods of landscape ecology and RS/GIS, the changes of land use pattern, suitability and optimized model of land resources, and ecological function zoning at Shanghuang Small watershed are studied by using the rich experiment data obtained from 1982 to 2008. At the same time, we explored the impact of land use classification and grid resolution on landscape metrics using the land use data base of this small watershed.The results and conclusions of this paper are as follows:⑴Impacts of grid resolution and land use classification on landscape metrics Most landscape metrics calculated from land use maps (grid date) were affected by grid resolution. The grain effect of landscape metrics was mainly affected by drawing scale rather than land use change, and the appropriate grain range for calculating landscape metrics from land use maps at 1:10 000 is from 5m to 15m. At the same time, landscape metrics aere affected by land use classification. Too detailed or too coarse classification system would generate greater impacts on these metrics, and the data in different historical periods are little impacts on the study of the response of landscape metrics to land use classification.⑵Dynamic change characteristics of land use patternAll land use types had undergone substantial changes in the Shanghuang small watershed from 1982 to 2008. According to the change of landscape matrix, land use change throughout the entire study period could be divided into three phases, i.e., grassland (1982-1990), cropland (1990-2002) and forest land (2002-2008). During the entire study period, grassland and cropland were decreased at the rate of 6.96%/yr and 3.40%/yr, respectively, and frost land, residential area and orchard were increased at the rate of 20.69%/yr, 2.12%/yr and 6.12%/yr, respectively. The driving forces of land use could be divided into three phases, i.e., adjust land use structure and improve the ecological environment (1982-1990); optimization of land use, rising of farmer's quality, and improvement of eco-economic benefits (1990-2002); and the overall advancement of reforestation.⑶Landscape pattern characteristics of land useThe area distribution of each land use type was extremely uneven. The largest area was forest land, and the second largest area is cropland, their area occupied 83.03% of the total area (806.39 ha). The index of SHAPE_AM showed that wetlands, unused land, forest land and grassland less affected by human activities, cropland and orchard greater, and residential area greatest. Affected by the human activities and national policy during the period from 1982 to 2008, the patch types of land use distributed more even, the fragmentation and heterogeneity of landscape increased first, and then decreased.⑷Analysis of land use in different slopeThe area distribution of each land use type in different slope was reasonable, which basically embody the principles of local conditions and rational distribution of resources. Seen from the implementation situation of reforestation, about 6.81 ha of land still need to reforestation, but this area was less than 1% of the total area. Therefore, the task of reforestation in this region was basic completed.⑸Suitability evaluation of land resourcesThe six metrics, including landscape position, slope, aspect, erosion intensity, soil organic matter and irrigation conditions, could be used as the index system for suitability evaluation of land resources. They could basically reflect the characteristics of land use resources of this region. The evaluation results showed that the area highly, moderately and barely suitable for agriculture were 115.57ha, 79.78ha and 121.11ha, respectively, and their area occupied 14.43%, 9.96% and 29% of the total area, respectively. The area suitable for forest land, grassland, and both forest land and grassland were 46.8ha, 419.04ha, and 139.86ha, respectively, and their area occupied 5.84%, 52.31%% and 17.46% of the total area, respectively.⑹Ecological function zoning of land useAccording to the analysis of land use pattern and the results of suitability evaluation of land resources, three functional regions were divided based on spatial structure optimization theory of landscape ecology. They were eco-environmental protection region in east mountain district, dry farming region in west mountain district, and high efficiency ecological agriculture region in flat district, respectively. The area of eco-environmental protection region in east mountain district was largest and occupied 51.84% of the total area. The surface erosion and gully erosion were very strong in this region for its broken terrain. The area of dry farming region in west mountain district occupied 33% of the total area, and the soil erosion was moderate for its gentle slope. The area of high efficiency ecological agriculture region in flat district occupied 15.16% of total region. There were flat land, deep soil and fertile soil, so it is rural settlement region.
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