基于坡位特征的黄丘区坡面植被恢复评价及模型构建

The Loess Hilly and Gully region is one of the most serious areas of soil and water loss in China and even the world. It is the key and difficult area of ecological construction, although ecological control has made great achievements. However, in the assessment of vegetation restoration at different slope positions, how to eliminate the misunderstanding of the pure pursuit of coverage in vegetation construction, and reduce the error of estimating soil and water conservation benefits based on vegetation coverage, and the comprehensive evaluation and model construction of vegetation restoration on small scale are weak. On the basis of previous studies, the project will take the Yangcuigou basin in Yan'an as the research area. Using TerraSAR-X to generate a large proportion of the region, 17 runoff plots with different spatial vegetation distribution were set up under the conditions of three vegetation coverage based on natural rainfall background and different spatial vegetation distribution, such as slope plot, gully slope plot and slope gully system runoff plot. The paper studies the runoff at different slope position and the same slope on different slope surface. The difference and spatial distribution pattern of sediment content, soil physical and chemical properties, reveal the influence of slope position on the soil and water conservation effect of vegetation and its control mechanism, and establish the slope factor, vegetation cover and vegetation distribution evaluation model, Based on the results of high score 2nd data interpretation, a vegetation distribution evaluation system with remote sensing image processing and spatial analysis function is developed to realize automatic extraction and evaluation of vegetation information at different slope position, which provides scientific reference for vegetation restoration and ecological security construction and management of slope ditch system in fragile area.

黄土丘陵沟壑区水土流失严重，尽管生态治理取得了巨大成效，但不同坡位植被恢复评估、如何消除植被建造中单纯追求覆盖率的误区、降低基于植被盖度估算水土保持效益的误差、小尺度上植被恢复综合评价与模型构建等研究薄弱。项目拟在前期研究的基础上，以延安市羊圈沟流域为研究区，使用TerraSAR-X生成区域大比例DEM，设置基于天然降雨背景的3种植被覆盖率和3个坡位条件下不同空间植被分布的野外原型坡面小区、沟坡小区和坡沟系统径流小区17个，研究同一坡面不同坡位及不同坡面相同坡位的径流、含沙量、土壤理化性质等差异性和空间分布格局，揭示坡位对植被水土保持效应的影响及其阻控机理；建立坡面要素、植被覆盖等提取及植被分布评价模型，并使用基于高分2号数据解译结果进行评价，开发具有遥感图像处理、空间分析等功能的植被分布评估系统，实现不同坡位植被信息自动提取和评价，为脆弱区植被恢复、生态安全建设与管理提供科学参考。

黄土丘陵沟壑区水土流失严重，尽管生态治理取得了巨大成效，但不同坡位植被恢复评估、如何消除植被建造中单纯追求覆盖率的误区、降低基于植被盖度估算水土保持效益的误差、小尺度上植被恢复综合评价与模型构建等研究薄弱。本项目选择黄土丘陵沟壑区具有明显坡沟系统地貌特征的吴起县柴沟流域作为研究区，建立了不同植被覆盖和空间分布格局的野外原型径流小区，在自然降水和放水冲刷相结合的试验条件下，开展了植被空间分布格局对坡沟系统侵蚀产流产沙调控机理的研究，取得了以下进展。(1)上方来水情况下，当植被覆盖度为75%且位于坡面下部时，对水动力过程的影响最大。与裸土坡沟系统相比，流速平均降低20.62%，阻力系数增加84.02%，减流、减沙效益分别高达21.12%、68.72%。自然降雨条件下，坡沟系统最优植被配置为高植被覆盖且位于坡面下部，与冲刷试验结果相一致。径流量和产沙量平均减少了45.34%、76.68%，减沙效益优于减流效益。(2)中下坡植被格局的蓄水减沙效益明显高于上坡，下坡植被格局的蓄水减沙效益略高于中坡，高植被覆盖度的蓄水减沙效益优于低植被盖度。(3)构建了植被位于不同坡位（上部、中部、下部）的水蚀产沙预测模型（R2=0.983、R2=0.995、R2=0.993）及水蚀产流预测模型（R2=0.989、R2=0.991、R2=0.986），为有效估算黄土高原坡沟系统侵蚀产流产沙提供了参考。(4)以Unet模型结构为基础，引入残差模块替换卷积模块加深网络结构，结合卷积注意力模块，排除无用信息以增加模型抗干扰性；优化激活函数与损失函数，增强了模型鲁棒性与精度，提出了一种改进型Unet深度学习模型。利用该模型训练数据集获得最优地形分割模型，并基于此模型提取了延安市地形和植被分布信息。研究成果为黄土高原水土保持效益精确评估及优化水土保持植被措施提供了有效参考，在脆弱区生态安全保障方面具有重要的科学价值和指导意义。