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深度聚类与谱聚类在农田管理分区中的适用性

Applicability of deep clustering and spectral clustering in farmland management zoning

  • 摘要: 管理分区是精准农业的重要环节,模糊C均值(fuzzy c means,FCM)与K均值(K-means)是常用的方法。随着数据规模的扩大及属性复杂性的增加,传统方法在处理高维和非线性数据时表现出一定的局限性。为此,该研究旨在通过引入谱聚类和深度聚类方法,与FCM和K-means进行对比,评估其在农田管理分区中的应用效果,为精准农业提供更科学的分区决策支持。研究以园区尺度的农田为研究对象,基于实地数据采集,采用综合权重法构建土壤综合肥力指数(soil fertility index,SFI),作为分区指标进行分区。通过Kappa一致性检验、平均轮廓系数(averaged silhouette coefficient,ASC)、方差比指数(Calinski Harabasz index,CHI)和方差分析,量化评估各方法的分区性能,并在案例区验证方法的适用性。结果表明,SFI有效反映了土壤肥力的空间分布,研究区中部肥力较高,东北部较低,整体土壤肥力较好;Kappa检验表明,深度聚类与FCM一致性最高(Kappa系数为0.767),谱聚类与深度聚类次之(Kappa系数为0.657),K-means一致性最低(Kappa系数仅为0.21~0.23);显著性分析表明,分区数为2或3时,各类别间差异显著,分区数为4时部分差异减弱;ASC和CHI指标显示,谱聚类方法在分区数为3时表现最佳,能够有效捕捉土壤属性与作物长势的空间变异性,各分区内各变量的变异系数均下降;在案例区进行分区验证的结果表明,谱聚类和深度聚类在不同区域均能有效区分管理单元,其中谱聚类表现最佳。综上所述,谱聚类在空间数据分区中的表现优于传统方法,生成的管理分区图能准确揭示研究区的空间异质性,适用于农田管理分区。

     

    Abstract: Management zoning is one of the most important procedures in precision agriculture. Among them, the fuzzy C-means (FCM) and K-means have been commonly used to divide the management zones. However, the conventional methods cannot treat the high-dimensional and non-linear data, due to the data scale and the attribute complexity. This study aims to introduce spectral clustering and deep clustering methods, compare them with FCM and K-means, and evaluate their performance in farmland management zoning, with the goal of providing more scientific decision-making support for precision agriculture. The research object was taken as the farmland at the park scale. According to the field data collection, the soil fertility index (SFI) was constructed to combine the comprehensive weight and multiple soil attributes. The spatial distribution of soil attributes was obtained to quantify the soil fertility level, which was input into the clustering model as a zoning indicator. The Kappa consistency test and analysis of variance were carried out to compare spectral clustering and deep clustering. A systematic evaluation was also made to explore their potential for the management of zoning in precision agriculture. The results showed that the soil fertility index better represented the spatial distribution of the soil fertility in the study area. The fertility level was relatively high in the central area, while the lower was observed in the northeast. The fertility level above the medium level (SFI≥0.5) accounted for 84.06% of the cultivated land, indicating the high soil fertility. The Kappa consistency test showed that there was the highest consistency between the deep clustering and the FCM (the Kappa coefficient was 0.767), followed by that between the spectral clustering and the deep clustering (the Kappa coefficient was 0.657). The consistency between the K-means and the rest was the lowest (the Kappa coefficient was only 0.209-0.234). The significance analysis shows that there were significant differences among the categories that were divided by the four clusterings when the number of clusters was 2 and 3. While there was no significant difference among some categories when the number of clusters was 4. The averaged silhouette coefficient (ASC) and the Calinski Harabasz index (CHI) showed that spectral clustering performed best when the number of clusters was 3. Its zoning was used to significantly distinguish the indicators, such as the soil nutrients, apparent electrical conductivity, vegetation index, and previous crop yield within different management zones. There was a decrease in the coefficient of variation of each variable within each zone. The spectral clustering effectively captured the spatial variability of the soil attributes and crop growth. There was consistency with the spatial distribution of the soil attributes after zoning. In conclusion, the spectral clustering was performed better than before in the spatial data zoning. The map of the management zoning was generated to more accurately reveal the spatial heterogeneity for the farmland management zoning. The finding can provide a more scientific and efficient zoning decision for precision agriculture.

     

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