| Gully area of Loess Plateau is a typical landform type of the Loess Plateau.The landform of this area is special.The highland surface is flat and open,and ravines are vertical and horizontal.The terrain is fragmented,the slope is steep,and the rainfall is uneven.It is one of the most serious soil erosion areas and the most vulnerable ecological environment in China.In this paper,Yongshou County,Shaanxi Province,a gully area in the dilapidated plateau,is used as the research area.The three phases of remote sensing images（1998,2008,2018）are used as the basic data,combined with soil,rainfall,vegetation,elevation,population,and economic data.The Arcgis software platform analyzes the landscape pattern changes and soil erosion in the study area,explores the mutual coupling relationship between the two changes,and explores its driving factors through geodetectors,in order to provide a theoretical basis for the local landscape pattern and soil and water conservation.The main findings of the study are as follows:（1）The dynamic change of landscape pattern in Yongshou County:The area change is due to the increase in the area of woodland and garden plots.The area of woodland increased from 183.44 km2 to 361.32 km2,and the area of garden plots increased from40.14 km2 to 168.80 km2.It comes from cultivated land and unused land.During the study period,the fastest increasing rate of single dynamic degree was garden land and forest land,which were 19.54%and 7.72%,respectively.The comprehensive dynamic degree during1998-2008 was 4.07%,which was higher than the comprehensive dynamic degree of 2.40%during 2008-2018.The center of gravity of other landscape types in Yongshou County migrated to the east.The center of gravity of the garden moved to the southwest.Among them,the unused land has the highest rate of migration and the fastest rate of change.In terms of landscape index,the spread index of the overall landscape decreased,the scatter and juxtaposition index,the Shannon diversity index,and the Shannon uniformity index increased,and the scatter index and landscape separation first decreased and then increased.It shows that the connectivity of the landscape is getting worse,the degree of fragmentation of the landscape is gradually increasing,and the types of landscapes are gradually divided into smaller patches.（2）Dynamic changes of soil erosion in Yongshou County:The annual maximum erosion modulus and average erosion modulus are decreasing year by year,the annual maximum erosion modulus ranges from 18481.77 t/（km2·a）to 14,801.48 t/（km2·a）,the average soil erosion The modulus ranges from 160.52 t/（km2·a）to 104.58 t/（km2·a）.Specifically,the soil erosion area of Yongshou County decreased year by year from 1998 to2008,which were 444.49 km2,427.62 km2 and 370.63 km2 respectively.The soil erosion type was mainly moderate erosion,accounting for 35.42%,39.42%and 38.50%of the total erosion area respectively.It can be seen from the changes in the transfer area of soil erosion that in 20 years,the soil erosion situation in Yongshou County has gradually improved.From 1998 to 2008,the area of the increased soil erosion level was 153.97 km2,and the area of the decreased part was 221.87 km2.From 2008 to 2018,the area of the increased soil erosion level was 115.16 km2,and the area of the decreased part was 285.6km2.In terms of the slope differentiation of soil erosion,micro-erosion is mainly distributed in the area below 10°,mild erosion is mainly distributed in the area below 25°,and strong,extremely strong and severe erosion is mainly distributed in the area of 15-25slope grade.（3）Research on the coupling of landscape pattern and soil erosion:From the perspective of landscape pattern and soil erosion,as the area of woodland and garden plots increases,the proportion of the area with erosion levels shows a decreasing trend.The erosion of the garden is minimal.From the perspective of soil erosion,forest land is the landscape type with the most severe soil erosion in Yongshou County,and its erosion area is increasing year by year,respectively 143.27 km2,213.86 km2,and 254.81 km2.However,the soil erosion rate is decreasing year by year,being 78.10%,65.79%,and 70.52%respectively.The soil erosion area of the garden first increased and then decreased,respectively 13.01km2,42.74km2,and 17.29 km2.Its soil erosion rate dropped from 32.41%in 1998 to 10.24%.From the perspective of soil erosion intensity,the soil erosion intensity index of forest land decreased by 40.36 from 1998 to 2008,and decreased by 10.42 from2008 to 2018.The soil erosion intensity index of garden plots increased by 10.16 from1998 to 2008,and decreased by 60.53 from 2008 to 2018.（4）Analysis of driving force based on geographic detectors:From the factor detection,it can be seen that each factor has different degrees of influence on the spatial distribution of soil erosion intensity.The least influence is the landscape aggregation index(x10),and the most influential is the slope（x3）,degree of human interference（x9）,degree of land use（x8）.Judging from the q values of these three influencing factors,the impact of human activities on soil erosion gradually exceeds that of natural factors.It can be seen from ecological exploration that some influencing factors have significant differences in the spatial distribution of soil erosion intensity.The ecological exploration results in 1998 were mostly the same as the ecological exploration results in 2008,and almost the same as the ecological exploration results in 2018.The two factors,the degree of land use（x8）and the degree of human disturbance（x9）,have important influences.It can be seen from risk detection that different ranges of different influencing factors have great differences in the spatial distribution of soil erosion intensity.The influence of each factor on soil erosion intensity is not a simple linear enhancement,but a nonlinear and dual-factor enhancement. |
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