基于多源遥感的东北黑土区切沟发育机制研究

Gully erosion is the main source of sand production in the black soil region of Northeast China. The development of gully erosion is closely related to time and spatial scales. It is of great significance to study the development mechanism of gully erosion at different time and spatial scales for gully erosion control in black soil regions. Combined with GIS spatial analysis methods, this project intends to describe different time scales (decadal-annual-seasonal) and different spatial scale (watershed-slope farmland-single channel) by using various remote sensing methods such as high-resolution satellites, low-altitude unmanned aerial vehicles, ground photography, and three-dimensional laser scanners. This project intends to 1) reveal the characteristics of development and evolution of gully erosion at different spatial and time scales in black soil; 2) extract relevant factors that affect the development of gully erosion, such as precipitation, geology, topography, soil, land use and vegetation, and excavate the main environmental factors that affect the development of gully erosion; 3) discriminate the time, position, and relative contribution of hydraulic erosion, freeze/thaw/melting snow, gravity, and other types of erosion forces through the seasonal three-dimensional shape changes of the gullies. Combined with indoor simulation experiments, we explored the effect of various forces combinations on the development of gully erosion. This project will reveal the developmental mechanism of the gully in the black soil area, deepen the study on gully erosion development mechanism in the black soil region, and provide theoretical guidance and scientific basis for gully erosion control in the black soil region of Northeast China.

切沟侵蚀是东北黑土区侵蚀沟产沙的主要来源，切沟侵蚀发育过程与时空尺度密切相关，研究不同时空尺度切沟侵蚀的发育机制对于黑土区沟蚀防治具有重要意义。本项目拟通过利用高分辨率卫星、低空无人机、地面摄影及三维激光扫描仪等多种遥感手段，结合GIS空间分析方法，分别定量研究不同时间尺度（年代际-年际-季节）和空间尺度（流域-坡耕地-单沟）的切沟侵蚀发育过程，揭示黑土区切沟侵蚀在不同时空尺度上的发育演变特征；进一步综合考虑降水、地质、地形、土壤、土地利用及植被等相关因素，挖掘影响切沟侵蚀发育的主控环境因素；同时通过切沟三维空间形态的季节变化监测判别水力、冻融/融雪、重力等多种侵蚀外营力组合的作用时间、位置和相对贡献，结合室内模拟试验探索多种侵蚀外营力组合对切沟侵蚀发育的作用影响，旨在揭示黑土区切沟的发育机制，深化黑土区沟蚀发育机理研究，为东北黑土区沟蚀防治提供理论指导和科学依据。

沟蚀过程与时空尺度密切相关，而多源遥感数据有助于全面反映不同时空尺度上的沟蚀演变特征，从而帮助我们理解多种侵蚀外营力组合作用下的黑土区切沟发育机制。在本项目的资助下，我们以吉林省九台区三岔河流域为研究区，采用高分辨率卫星影像、无人机遥感等多种遥感手段，研究了切沟侵蚀在不同时空尺度上的发育演变特征，并对影响沟蚀发育的主控环境影响因素进行了挖掘，结合室内模拟土壤冻融实验，揭示多种侵蚀外营力组合对切沟发育的作用影响。研究结果表明：（1）1965-2018年侵蚀沟的数量增加了17.95%，变化最剧烈的区域集中在流域的东北部；（2）研究区坡耕地横坡耕作的趋势非常明显，耕地垄向角与沟蚀密度和裂度显著负相关，而岩性和土壤类型是影响沟蚀空间分异的主要因素；（3）沟头侵蚀始终是侵蚀沟产沙的主要来源，2015-2020年的沟头线性、面积、体积侵蚀速率分别为0.74m/year、7.29m²/year、9.66m³/year，该结果要低于东北黑土区北部地区的现有研究成果，这与南部地区坡长较短、冻融时间更短、解冻期间的温差更小有关，而沟头体积侵蚀速率与年总降雨量密切相关（R²=0.958，P=0.042）；（4）侵蚀沟在雨季以沟头扩张和净侵蚀为主，而冬-春季沟壁出现冻胀裂缝，没有明显的净侵蚀。室内冻融实验结果也表明研究区土壤抗剪强度随冻融循环次数和初始土壤含水量的增加而降低，与黑土区北部不同的是，研究区沟壁坍塌主要发生在雨季。雨季沟头侵蚀占全年线性侵蚀的94.62%，占面积侵蚀的87.64%。尤其是雨季初期，沟壁坍塌和沟头扩展占主导地位，占全年线性侵蚀的66.67%，占面积侵蚀的49%。本项目的研究成果可为东北黑土区沟蚀防治提供理论指导和科学依据。