Landscape Pattern Evolution In The Xiangshui Watershed Study On The Relationship Between Soil And Water Loss

Landscape pattern determines the process of soil and water loss.Exploring the impact of landscape pattern evolution on soil and water loss can be of great significance for future landscape pattern optimization and targeted suggestions for soil and water loss control.In this paper,the Xiangshui watershed in the red soil region of southern China is taken as the research object.Through the analysis of hydrological factors in the basin from 1963 to2020,the evolution of landscape pattern from 1995 to 2020,and the prediction of landscape pattern in 2025,the influence of landscape pattern evolution on soil and water loss is explored,and targeted suggestions are put forward for the future landscape pattern optimization and soil and water loss control.The main conclusions are as follows:(1)The average annual runoff depth,sediment concentration and sediment transport in Xiangshui watershed from 1963 to 2020 showed a downward trend,and the distribution of the three was uneven during the year,mainly concentrated in April to June.The wavelet analysis results showed that the three had multiple time scales of alternation of abundance and dryness,and the main change periods were 30 years(runoff depth),28 years(sediment concentration)and 27 years(sediment transport).(2)During 1995-2020,the area of cultivated land and residential land increased,the area of forest land and grassland decreased,and the change of water area was not obvious.There are great differences in various types of landscape.Forest land is an absolute dominant landscape element in the Xiangshui watershed,with a large proportion of forest land,large plaque area and high connectivity.The index of cultivated land and residential land fluctuates greatly,and the overall landscape pattern index changes obviously.(3)(1)At the type level,the marginal density of cultivated land,landscape shape index,and area-weighted average shape index were positively correlated with the sediment yield in Xiangshui watershed;the patch density of forest land is the main factor affecting the characteristic variables of soil and water loss,and the separation degree is the main inhibitory factor of sediment discharge and sediment transport modulus.The influence of grassland on soil and water loss mainly depends on the shape of grassland;the percentage of water landscape types and runoff and sediment production have inhibitory effect,but the degree of separation has a promoting effect on runoff and sediment production.The density,area size and distribution of residential land have inhibitory effects on runoff and sediment yield in the basin.(2)At the landscape level,the patch density,landscape fragmentation,Shannon diversity index,evenness index and modified Simpson evenness index,which were negatively correlated with runoff and sediment yield,increased year by year.CCA analysis showed that the most important factor affecting soil and water loss was patch density.(4)The prediction accuracy of CA-Markov model meets the research requirements.From 2020 to 2025,the change of various land use types in Xiangshui watershed is relatively small.On the whole,the landscape pattern of Xiangshui watershed in 2025 is beneficial to soil and water conservation.However,there is still a risk of increasing soil erosion at the level of landscape pattern index at the type level.For example,the patch density of forest land and the connectivity of grassland and the separation of water areas are all fluctuating in the direction of promoting soil erosion.Therefore,in the future soil erosion control and landscape pattern optimization process,we should focus on the shape and slope direction of cultivated land,the spatial distribution of forest land and grassland,and the dispersion of water area.