郭澎涛, 茶正早, 罗微. 基于归一化植被指数获取环境因子权重的土壤管理分区方法[J]. 农业工程学报, 2023, 39(3): 60-67. DOI: 10.11975/j.issn.1002-6819.202208189
    引用本文: 郭澎涛, 茶正早, 罗微. 基于归一化植被指数获取环境因子权重的土壤管理分区方法[J]. 农业工程学报, 2023, 39(3): 60-67. DOI: 10.11975/j.issn.1002-6819.202208189
    GUO Pengtao, CHA Zhengzao, LUO Wei. Acquiring environmental factor weights using normalized difference vegetation index for soil management zoning[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2023, 39(3): 60-67. DOI: 10.11975/j.issn.1002-6819.202208189
    Citation: GUO Pengtao, CHA Zhengzao, LUO Wei. Acquiring environmental factor weights using normalized difference vegetation index for soil management zoning[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2023, 39(3): 60-67. DOI: 10.11975/j.issn.1002-6819.202208189

    基于归一化植被指数获取环境因子权重的土壤管理分区方法

    Acquiring environmental factor weights using normalized difference vegetation index for soil management zoning

    • 摘要: 在基于加权环境变量进行土壤管理分区时,常利用作物产量与环境变量之间的关系来获取环境变量的影响权重。然而,当作物产量难以获取或作物产量与环境变量之间不能建立关系模型时,这种基于作物产量获取环境变量影响权重的方法将不再适用。针对此问题,该研究基于归一化植被指数(normalized difference vegetation index,NDVI)可以反映土壤条件而土壤条件又受环境变量影响,提出一种利用NDVI获取环境变量影响权重的方法,并将其应用于橡胶园土壤管理分区。结果表明,利用该方法可以筛选出与NDVI关系紧密的15个关键环境变量,并且可以获取这些环境变量的权重,其中,前5个环境变量(坡向正弦和余弦,地形位置指数,地形湿度指数,剖面曲率)的权重几乎占到15个环境变量权重之和的一半。利用加权后的环境变量可将研究区橡胶园划分为6个分区。这些分区可以很好地区分不同土壤养分(土壤有机质、全氮、有效磷和速效钾)的丰缺水平。同时,不同分区间环境变量的差异也达到了显著水平(P<0.05)。可见,该研究提出的利用NDVI获取环境变量影响权重的方法是可靠的。研究可为土壤管理分区提供可靠的思路。

       

      Abstract: More reasonable soil management zones can be made using weighted environmental factors as cluster variables. Weights of the environmental factors are generally acquired from the relation between crop yields and environmental variables. However, it would be impossible to obtain the weights in the case that no relation exists between crop yields and environmental variables or there are no crop yields available. Fortunately, the normalized difference vegetation index (NDVI) can be expected to reflect the soil condition, which was significantly influenced by the environmental variables. In this study, an accurate and efficient approach was developed to obtain the weights of environmental variables using NDVI. The relation model between NDVI and environmental variables was then established in this case. Three steps consisted of this approach. Firstly, the key environmental variables were selected to significantly impose the influence on NDVI. The relation model was then established between NDVI and the selected key environmental variables. Finally, the weights of environmental variables were acquired from the established relation model. A case study was applied to test the effectiveness of the approach. Specifically, the weights of environmental variables were acquired for a rubber plantation in Danzhou County, Hainan Province, China. Among them, the candidates were taken as the 10 terrain attributes, 19 bioclimatic variables, and 5 parent materials types. Furthermore, 15 key environmental variables were determined to construct the relationship model with the NDVI using the random forests (RF). The importance index was extracted from the fitted relation model, and then calculated the weight of each key environmental variable. These acquired weights were also used to weigh the environmental variables, and then to serve as the input variables for the K means clustering. Finally, six groups of soil management zones were generated for the rubber plantation. A total of 1 296 top soil (0-20 cm) samples were employed to verify the soil management zones. Results indicated that the management zones better distinguished the abundance and deficiency levels of different soil nutrients (soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP), and available potassium (AK). Zone 1 presented the high AP content, the normal range of pH value and SOM content, as well as the TN and AK in deficiency. Zone 2 shared the high AP content, pH value suitable for the rubber tree growth, but the SOM, TN, and AK in deficiency. Zone 3 demonstrated a very high AP content anda pH value within the normal range. Nevertheless, the contents of SOM, TN, and AK were all lower than the normal range in Zone 3. More importantly, the contents of SOM, TN, and AK in Zone 4 were similar to those in Zone 3. However, the values of pH and AP were significantly lower than that in Zone 3. In Zone 5, the values of pH and AK were the highest in the normal range among the six zones, while the values of SOM and TN were the lowest in deficiency. In Zone 6, the soil TN content wasthe highest among the six zones within the normal range. The pH value and AP were also within the normal range, but the APcontent was close to the lower limit of the normal range, indicating the insufficient content of SOM and AK. At the same time, the mean differences were all significant at the 0.05 level in 15 selected environmental variables among different management zones. Consequently, the soil management zones further verified the effectiveness of the approach, where the weights of environmental variables were acquired by the NDVI. Anyway, the NDVI acquiring the weights of environmental variables canbe applied to much wider ranges, because the NDVI can be much easier to access than the crop yields in practice.

       

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