| The 20th National Congress of the Communist Party of China called for consolidating the foundation of food security in all areas,fully implementing the Party and government responsibilities for food security,and keeping the red line of 1.8 billion mu of arable land firmly in place to ensure that the Chinese people’s rice bowl is firmly in their own hands.The phenomenon of farmland abandonment is increasingly common in the environment of rapid economic development,and the contradiction between farmland non-grain and food security is increasingly prominent.Meanwhile,farmland abandonment and its ecological security problems have gradually become a research hotspot in the academic circle.The research object of this paper is Ruzhou City and the Funiu Mountain area,which is a typical mountain agricultural and food producing area,and also a national key control area of soil and water loss.Therefore,the contradiction between arable land resources and ecological environment caused by the abandonment phenomenon needs to be paid attention to and solved.Clarifying the spatial distribution characteristics of abandoned land in Ruzhou can provide technical support for the management of regional farmland abandonment and the decision of spatial control of soil and water conservation.In order to achieve the above goals,based on high spatial resolution image and multi-spectral remote sensing image,this study adopted the supervised classification method,carried out threshold segmentation of remote sensing image,established the identification method of abandoned land in the study area,and extracted the spatial distribution of abandoned land in the study area.Combined with the influencing factors of spatial pattern,the spatial distribution characteristics of abandoned land and the driving mechanism of spatial factors(altitude,slope,slope length,tillage distance,etc.)in the study area were analyzed.At the same time,based on the CSLE model and SCS-CN model,the soil erosion characteristics and runoff under the influence of abandoned land in the study area were estimated,and the influence characteristics of the current abandonment phenomenon on regional sediment yield and runoff were proposed.The main research conclusions are as follows:(1)Based on remote sensing image recognition and classification,the total area of abandoned land in the study area is 25.95km~2,and the abandonment rate is 4.26%.The abandoned land is characterized by small plain area,large hilly area and large quantity.The abandoned land in the study area is mainly distributed in the mountainous areas in the south and north of Ruzhou City,and the patch area of the abandoned land is small.Among them,large areas of arable land are prone to be abandoned in the areas with higher elevations.In the transition areas between plain and mountain areas,there is also a certain area of abandoned land due to industrial development or large household contracting.(2)The abandonment rate of cultivated land in the study area was affected by different spatial pattern factors.On the whole,the abandonment rate increased with the increase of tillage distance.In the area with tillage distance of 1100-1200m,the abandonment rate reached 9.23%.The abandonment rate gradually increases with the increase of altitude.The abandonment rate is the largest in the area with an altitude of 200-400m,and 8.91%in the area with an altitude greater than 500m.The abandonment rate was lower in the areas with slopes below 10°,and the abandonment rate of 10-20°,20-30°,30-40°and above 40°were3.0,2.7,2.3 and 3.8 times,respectively.Most of the areas with slope length of more than100m are distributed in hilly and mountainous areas,and the abandonment rate of arable land in these areas is at a relatively high level,with an average abandonment rate of more than 5%.(3)Abandoned land can reduce the hydraulic erosion area of the study area.Compared with the cultivated land of the same area,the abandoned land can reduce 85.84%of the erosion area(the land area with mild erosion and above erosion grade).Under the current abandonment rate(4.26%),the abandoned land can reduce 3.07%of the overall cultivated land area in the study area(land area with mild erosion or above erosion grade),and 1.86%of the whole city’s erosion area(land area with mild erosion or above erosion grade).(4)Abandonment of farmland can improve regional water conservation function.The simulation results based on SCS-CN showed that the abandoned land could reduce the annual runoff by 81.89%compared with the cultivated land of the same area.Under the current abandonment rate,abandoned land can reduce the annual runoff of 4.28%of the total cultivated land area in the study area. |
