基于SOFM与随机森林的大别山区水土保持空间管控分区

Spatial control zoning of soil and water conservation in Dabie Mountains using self-organizing feature map and random forest

水土保持是国家生态文明建设的重要内容,水土保持空间管控分区是水土流失区域科学治理的前提与关键。然而,目前水土保持管控区域划分研究还未形成成熟的空间划定方法,且以小流域为单元的水土保持空间管控研究较少。为探索水土保持空间管控分区的方法,落实差别化保护治理措施,该研究利用通用土壤流失方程(universal soil loss equation,USLE)计算研究区潜在土壤侵蚀模数与实际土壤侵蚀模数,并通过随机森林确定了土壤侵蚀的主要影响因子,基于小流域单元的土壤侵蚀及其影响因子利用自组织映射神经网络(self-organizing feature map,SOFM)确定了大别山区的水土保持空间管控分区。结果显示:1)大别山区的平均潜在土壤侵蚀为84 415.7 t/(km^(2)·a),平均实际土壤侵蚀为210.25 t/(km^(2)·a)。小流域的实际土壤侵蚀主要分布于0~300 t/(km^(2)·a),小流域尺度上潜在土壤侵蚀与实际土壤侵蚀空间分布格局基本一致,高值区主要分布于研究区中部与东部海拔较高的山区腹地;2)植被覆盖度、坡度分别为小流域尺度上潜在土壤侵蚀与实际土壤侵蚀的主要影响因子,植被覆盖度、坡度与土壤侵蚀呈显著正相关(P<0.01)。高植被覆盖区主要分布于林地占比较高的大别山区腹地,坡度较大的区域沿大别山山脊线自西向东分布。3)SOFM结果显示,小流域尺度上的大别山水土保持空间管控区域划分为重点预防区、一般预防区与其他区域,其中重点预防区涉及小流域710个,面积15 287.4 km^(2)。一般预防区共890个小流域,面积18 874.4 km^(2)。两个预防区面积共占研究区61.2%。各区域间的实际土壤侵蚀、潜在土壤侵蚀与坡度差异明显,可作为大别山水土保持空间管控各区域的主要划分指标。研究结果为水土保持空间管控分区提供了思路,为分区域进行水土保持空间管控提供了理论支持与决策依据。

Soil and water conservation is one of the most important parts of the national ecological civilization.The spatial control area of soil and water conservation can be divided to effectively manage the soil and water loss regions.However,it is still lacking in the spatial delineation in the regional division of soil and water conservation.Only a few studies have been focused on the spatial control of soil and water conservation,according to the small watershed.This study aims to explore the spatial control zoning for soil and water conservation,and then implement the differentiated protection and management measures.The universal soil loss equation(USLE)model was used to calculate the potential and actual soil erosion.The main influencing factors of soil erosion were determined by random forests.A self-organizing feature map(SOFM)was used to determine the spatial control zone of soil and water conservation in the Dabie Mountain area on a small catchment scale.The results showed that:1)The average potential and actual soil erosion were 84415.7 t/(km^(2)·a)and 210.25 t/(km^(2)·a),respectively.The actual soil erosion was distributed mainly in 0-300 t/(km^(2)·a)at the small watershed scale.There was the basically same distribution of spatial patterns under the potential and actual soil erosion.The high-value area was distributed mainly in the central and eastern mountain areas at the high elevation.2)Vegetation coverage and slope were the main influencing factors of potential and actual soil erosion at the small watershed scale,indicating a significantly positive correlation with the potential soil erosion(P<0.01).The high vegetation cover area was concentrated in the hinterland of Dabie Mountain.The high slope area was extended from the west to the east along the ridgeline of Dabie Mountain.3)The SOFM results showed that the spatial control zone of soil and water conservation was divided into three areas:key prevention,general prevention,and the rest area at the small watershed scale.Among them,the key prevention area involved 710 small watersheds with an area of 15287.4 km^(2).There were 890 small watersheds in the general prevention area,covering an area of 18874.4 km^(2).Two prevention areas accounted for 61.2%of the study area.There was an outstanding difference between actual and potential soil erosion and slope among regions.The classification index can serve as the spatial control of soil and water conservation.The finding can provide theoretical support and decision-making on the spatial control regionalization for soil and water conservation.