Evolution Of Land Use Pattern And Its Soil Environment Effects In Loess Hilly Region

Loess plateau is one of the most serious areas in our country in soil erosion. Landscapepattern changes driven by human have a significant impact on regional eco-environment andglobal change. Studying evolution rule of land use pattern and its soil environmental effectshelp control soil erosion and regulate reasonable planning and management of land use.Another important meaning is that studying that help people explore ecological effects ofhuman activities. Taking Yanhe Basin as study area, this essay studied the land use patternevolution rule and its effects on soil environment. The results are as follows:(1) Grassland is the matrix landscape in Yanhe Basin while woodland landscape was thesecond largest one. The changes of farmland were significantly affected by the policy andland use planning. Water area increased gradually because of more and more irrigationfacilities as well as ever-increasing awareness of protecting the environment. During the past20years, construction land and unutilized land had been the smallest landscape type in thewhole watershed. Landscape pattern changes are affected by many factors, such as policyplanning, economic situation, humanistic custom, as well as the climate, hydrology. The areaof farmland decreased first and then increased. The shape and distribution of farmland wereregularized first and then complicated. Though the area of grassland had reduced most, it wasthe matrix landscape in Yanhe Basin. The degree of fragmentation of grassland patch wasaggravated. During the years between2000and2010, woodland patch type grown more thanother landscape and its shape became regularized. The degree of fragmentation of woodlandalso continued to be weaken and its degree of connection continued to be enhanced. The areaof construction land, water area, and unutilized land were small and the changes of them werenot obvious.(2) The degree of diversity and quality were ever-increased during the past20years atthe landscape level. The shape of landscape patch became simple between1990and2000 while it saw a trend to be more complicated between2000and2010. In terms oftransformation of landscape types, the input and output of grassland were more than any otherlandscape types.(3) The land use pattern of different vegetation zones pattern were various. Grasslandaccounted for the highest in the grass zone. The two largest landscape types were grasslandand woodland, the total of which was much larger than others. Woodland landscape accountfor most in forest zone and its dominating role was obvious. Because of its large area,woodland have a significant impact on the environment. The distribution of the samelandscape patch in grass zone and forest zone were similar and the degree of aggregation ofwoodland in forest zone was obvious. The richness of vegetation was high while theaggregation was slightly low. Landscape indexes had obvious size effects. With the increaseof particle size, indexes showed different variation trend. The optimum particle size range oflandscape analysis for Gaojiagou watershed was between75and120m.(4) In terms of soil nutrient selected from seven typical landscape types in study area,soil moisture content showed: farmland> orchard> woodland> arbor-shrub land> naturalgrassland> artificial grass land> shrub land. During the years between1990and2010, thecontribution rate of soil moisture of grassland had dropped while that of forest land increased.In terms of different landscape types, the content of organic matter, total nitrogen, and totalphosphorus became less with the deepening of the soil. In the same soil layer, the content oforganic matter, total nitrogen, and total phosphorus of grassland was highest. As soil layerdeepen, the degree of variation of organic matter in farmland, artificial grassland decreasedwhile that in natural grassland, arbor land, and shrub land increased. As the soil layer deepen,the degree of variation of total nitrogen in farmland and natural grassland increased while thatin artificial grassland, arbor land, and shrub land decreased. As soil layer deepen, the degreeof variation of total phosphorus in farmland, artificial grassland, natural grassland increased.According to soil erosion distribution standards of the ministry of water resources, the soilerosion in Yanhe Basin was mainly moderate. As landscape pattern changed, the one of2000were intense while that of2010declined.