结合RF和LandTrendr算法的黄河流域下游撂荒耕地精准提取与时空变化分析

    Precise extraction and spatiotemporal analysis of abandoned cultivated land in the Lower Yellow River Basin using RF and LandTrendr algorithms

    • 摘要: 耕地撂荒是一种常见的土地利用与覆被变化现象,深刻影响着全球的农业生产和粮食安全。黄河流域作为中国重要的粮食生产基地,监测其撂荒耕地时空动态变化并分析其原因具有重要的现实意义。该研究以黄河流域下游兰考县、长垣县、封丘县和东明县为研究区,依托 Google Earth Engine(GEE)云平台,结合2004—2022年Landsat长时间序列影像,并通过分层随机采样与目视解译相结合的方式构建样本集,结合多维度特征,综合应用随机森林概率模型及LandTrendr变化检测方法,系统地提取撂荒耕地与休耕地,并对其动态变化进行深入分析。结果表明:1)基于土地覆被变化提取2022年撂荒耕地与非撂荒耕地的F1分数分别为0.80和0.87,而结合变化检测方法提取2004—2022年撂荒耕地,撂荒耕地与非撂荒耕地的平均F1分数分别达到0.87和0.89,精度显著提升;2)研究区撂荒耕地面积在2004—2022年间呈现先上升后波动式下降的趋势,平均面积为28.24 km2,2007年达到峰值49.35 km2,而休耕地分布零散且面积较小;3)农业机械化水平的提升有效遏制了撂荒现象,而粮食产量的提升可能会带来撂荒风险的增加,第一产业就业人数对撂荒影响有限。该研究通过结合随机森林与LandTrendr算法,实现了对撂荒耕地的精准提取,并揭示其变化趋势及影响因素,这为黄河流域下游制定针对性的农业政策,保障国家粮食安全提供了参考。

       

      Abstract: Cultivated land is the foundation of agricultural development and a basic condition for ensuring human survival. With the rapid development of urbanization, which has increased non-agricultural employment opportunities and income, rural populations have migrated to urban areas, leading to large-scale abandonment of cultivated land. This phenomenon profoundly impacts national agricultural production and food security. As the Yellow River basin is a vital grain production base in China, accurately and efficiently obtaining the spatial distribution of abandoned cultivated land is crucial for preventing the further spread of this trend, holding significant theoretical and practical importance.This study focuses on the downstream regions of the Yellow River, specifically in Lankao County, Changyuan County, Fengqiu County, and Dongming County. It utilizes Landsat imagery from March to October, spanning the years 2003 to 2023, with the data undergoing preprocessing for this period. Considering the differences between cultivated land and other land types, spectral features, vegetation indices, texture features, topographic features, and Kauth-Thomas features were extracted to construct feature sets for each year from 2003 to 2023.A combination of stratified sampling and visual interpretation was employed to obtain the sample sets. This study employed a random forest probability model combined with the LandTrendr change detection method to extract abandoned and fallow lands, excluding urban areas.The accuracy of the abandoned cultivated land results was validated using the F1-Score, and the factors influencing abandoned cultivated land were analyzed. The results indicate that in the random forest probability model, EVI_p80, NDVI_p80EVI, and nir had high importance and discriminability in the output. Statistical analysis of the area of abandoned and fallow land within the study area revealed that from 2004 to 2022, the area of abandoned cultivated land followed a trend of initial increase followed by fluctuating decline, with an average area of abandoned cultivated land of 28.24 km2. The maximum area of abandoned cultivated land was reached in 2007, amounting to 49.35 km2. After 2020, the phenomenon of abandonment was effectively controlled. The area of fallow land was found to be relatively small and scattered. Utilizing the random forest probability model in conjunction with the LandTrendr change detection method, an F1-score of 0.87 was achieved for abandoned cultivated land, while a score of 0.89 was obtained for non-abandoned cultivated land, showing an improvement in accuracy compared to land cover change-based extraction. This demonstrates the effectiveness of the method for monitoring abandoned land in the Yellow River basin. To investigate the factors influencing the aabandoned ccultivated land, a multivariate regression analysis was conducted, incorporating total agricultural production value, total mechanical power, grain production, and the number of employed individuals in the primary industry, in relation to the area of abandoned cultivated land. The results indicate that an increase in the level of agricultural mechanization effectively reduces the abandonment of cultivated land, while an increase in grain production may raise the risk of abandonment. Although the number of employed individuals in the primary industry has decreased, its impact on land abandonment is limited, with policy regulation playing a significant role. The implementation of strict cultivated land protection policies has effectively reduced the area of abandoned cultivated land, which is crucial for ensuring national food security and promoting the sustainable development of agriculture. This study not only provides an effective technical approach for monitoring abandoned cultivated land in the Yellow River basin but also offers an in-depth analysis of the spatiotemporal changes and driving factors of cultivated land abandonment, providing valuable references for the formulation and implementation of agricultural policies in China.

       

    /

    返回文章
    返回