Modelling LUCC Effects On Soil Erosion Rates Of A Chinese Loess Plateau Catchment Based On RUSLE And PESERA

In order to control soil erosion,since the 1950s a large-scale soil and water conservation measures have been implemented on the Chinese Loess Plateau.Since 1999,a large scale ecological restoration program entitled 'Grain-for-Green Project(GGP)'has been implemented on the plateau.These measures have dramatically changed the land use/cover pattern of the Loess Plateau,and in recent years,the warming and drying of the climate has also affected vegetation growth,altering the land use/cover pattern of the Loess Plateau.Therefore,land use/cover change(LUCC)and its impact on soil erosion on the Loess Plateau have become a hot research topic.Soil erosion model is an effective tool for assessing soil erosion rates and its response to LUCC on the Loess Plateau.However,previous studies have only employed individual models to achieve the above research objectives.No studies used multiple models and compared results of different models,strongly contstrainting the selection and development of soil erosion models for the Loess Plateau.This study investigated the LUCC in a typical Loess Plateau catchment(i.e.,Huangfuchuan)before and after the GGP(1990,2000 and 2011).Two widely used soil erosion models(RUSLE and PESERA)were then used to study the impact of LUCC on soil erosion rates in the Huangfuchuan catchment,and their modelling results were compared.The findings can benefit the development of land management strategies and further development of regional scale soil erosion models for the Loess Plateau.The main findings are as follows:(1)LUCC of the Huangfuchuan catchment.From 1990 to 2011,the land use/cover in the Huangfuchuan catchment has changed significantly.Grassland accounted for the majority of the area in the catchment,the proportion is between 70%and 80%.Other land use types(unused land,cropland,sandy land,water body,forest and residential land)accounted for a smaller area.Between 1990 and 2011,the area of land use/cover types in the catchment have experienced different fluctuations:the area of grassland and residential land experienced a"rising trend",the cropland and forest experienced a"falling trend",and the sandy land and unused land experienced a fluctuation swifting from"rise"to"fall";The land use/cover types exchanged frequently between 1990 and 2011:In terms of land use degree,the basin belonged to a recession period in 1990-2000 and an adjustment period in 2000-2011,and the vegetation coverage increased from 38.3%in 1990 to 48.7%in 2011.(2)Modelling of the impact of LUCC on soil erosion rates.The average soil erosion rates of the Huangfuchuan catchment predicted by RUSLE and PESERA increased first and then decreased under the LUCC during 1990-2000 and 2000-2011.The RUSLE and PESERA modelled soil erosion rate for different land use/cover types usually follow:sandy land and unused land>cropland and grassland>forest,so sandy land and unused land should be the focus of future soil and water conservation work.In 1990,2000 and 2011,except for the unused land,the RUSLE and PESERA modelling results are consistent:grassland,cultivated land and woodland were mainly subject to moderate to moderate erosion,while sandy land mainly suffered from moderate to severe erosion.On the land use/cover type transition area,modelling results of RUSLE and PESERA showed that the soil erosion rate decreased on areas where land use/cover was converted into forest or grassland,and soil erosion rates on the former decreased more than the latter,and soil erosion rates increased when land use/cover was converted into sandy land and unused area.Soil erosion rates on steep slopes(i.e.>25°)were predicted to increase under the 2000-2011 LUCC,which may be due to the limited vegetation growth caused by the serious lack of soil moisture,implying that further work is still needed to study soil erosion processes and their conservation on steep slopes.(3)Comparison of RUSLE and PESERA modelling results.RUSLE predicted considerably higher soil erosion rates than PESERA under different LUCCs.The spatial distribution of soil erosion rates predicted by RUSLE and PESERA is poorly correlated.Regarding the modelling results of land use/cover type transition zones,RUSLE and PESERA modelling results showed the same trend in the forest transition zone and sandy land transition zone(except for the unchanged zone).In other transition zones,changing trends of RUSLE and PESERA modelling results are not always the same.Model comparisons showed that RUSLE is more sensitive to slope gradients while PESERA is more sensitive to vegetation cover,and the discrepancy between their modelling results(RUSLE erosion predictions>PESERA erosion predictions)increased with slope gradients.PESERA may need improvement to better account for steep slope erosion processes on the Loess Plateau,while RUSLE may need improvement in the description of vegetation effects.