| Terrace is an effective measure to prevent soil erosion in the hilly and gully areas of the Loess Plateau,and it is also an important measure to ensure the agricultural production and food security in the loess hilly region.In this paper,the terraced fields of Guanchuan River Basin were studied by means of spatial analysis,RUSLE model,contribution coefficient and principal component analysis.The temporal and spatial dynamics of terraced fields in Guanchuan River Basin from 1998 to 2015 were studied in this paper.Characteristics of terraced land construction and its influence on soil and water loss.The main conclusions are as follows:(1)From 1998 to 2008 on the Guanchuan River Basin terrace area of 35.42% annual growth rate of 2008 to 2015 of the valley terrace area of 5.74% annual growth rate on the Guanchuan watershed terrace area increased quickly after the first rate and gradually slowed down;with the terrace area range,terrace field tended to decrease,mainly in small plots of Terraced fields distribution;multi terraced fields at an altitude of 1900 ~ 2300 m,the slope of 5 degrees to 25 degrees east and southeast slope,slope,slope and slope to the West southwest,and continuous large terrace is mainly distributed in the altitude of 2100 ~ 2300 m,the slope of 5 degrees to 15 degrees on the southern slope of the hill.(2)The terrace on the Guanchuan watershed is one of the main landscape types,the landscape occupies a total area of 3.57% from 1998,16.39% in 2008,increased to 22.58% in 2015,has an important role in the whole landscape;due to human interference more terrace landscape types of simple shape and the degree of fragmentation is serious,but with the increase of Terrace Construction of the year.AWMSI terraced landscape types,and the average patch fractal dimension,area weighted mean patch fractal dimension is increased,indicating that human on the terraced landscape effect diminished.(3)Guanchuan River Basin from 1998 to 2015,the average soil erosion modulus decreased,the average soil erosion amount in 1998 from 12644.15t/km-2·a-1,2008 years 8885.96t/km-2·a-1 to 7926.68t/km-2·a-1 in 2015;on the Guanchuan watershed soil erosion grade structure has undergone great changes,from 1998 to 2015,the extreme erosion and severe erosion area greatly decreased,decreased by 30.53% and 46.41%,other grades of erosion area increased,indicating on the Guanchuan watershed soil erosion has been effectively controlled.(4)The distribution area of river basin and close the terrace distribution of soil erosion modulus of non significant difference in the distribution of terraced mild erosion and moderate erosion,non terraced area dominated by very strong erosion.The terrace and non terrace for the average contribution of change of soil erosion in the study area the rates were 21.45%,78.55%,indicating that the soil erosion from the terrace is less than the amount of soil erosion from non terraced fields,water and soil conservation effect than non terrace.(5)Guanchuan River Basin climate and geographical factors is one of the factors driving the construction of terraces,spring and winter cold and dry,and more wind,summer rain,and the rainfall is relatively concentrated,the larger area of cultivated land scarce natural slope and loose soil,vegetation and soil erosion is very serious;the population is the most important factor in human the social and economic factors,one of the driving forces of terrace construction changes and the most dynamic,on the Guanchuan watershed high population density,per capita grain yield is far lower than the national average,yield terrace can alleviate the problem of low per capita grain yield;Guanchuan River Basin Economic Development Model,the industrial structure also has a great driving effect on the terrace construction;the government policy is extremely effective driving factors.The social and natural factors have great effect on the terrace on the Guanchuan watershed changes,but little overall social effect on the terrace changes larger than natural factors. |
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