照片样线法大豆植被覆盖度测量精度分析

Accuracy Analysis of Soybean Vegetation Coverage Measurement by Photo Line Transect Method

植被覆盖度是单位面积内植被垂直投影面积占总面积的百分比,它是重要的生态学参数,同时也是大豆等农作物的重要农艺参数。理想的覆盖度测量耗时短,工具简单,结果准确,受人为因素影响小。本文以‘黔豆3号’‘、川豆16’和大黑豆等24个品种为研究对象,以照相法测量值作为参考,分析目估法、实地样线法和照片样线法测定大豆植被覆盖度的精度和适用性。结果表明:目估法测量的植被覆盖度误差最大,平均为7.8%,目估误差随株高的增高呈现出先增加后降低的趋势。实地样线法测量精度较高,误差小于3%(2.8%),但耗时最长,每个1 m×1 m样方需用时6.2 min。照片样线法误差小于3%,几乎不需要消耗野外采样时间,室内每个样方照片处理需耗时约3.0 min。相较于目估法,照片样线法具有更高的测量精度,相较于实地样线法,照片样线法能够节省野外采样时间,提高工作效率。因此推荐照片样线法作为大豆和类似植物覆盖度的测量方法,同时两条样线(样线长度合计为2.8 m)即可满足测量误差小于5%的精度要求。未来应进一步探索照片样线法在其他作物覆盖度测量中的适用性。

Vegetation coverage is the percentage of the total ground area covered by the vertical projected area of vegetation.It is an important parameter in ecology and an important agronomic index of crops such as soybean.The ideal coverage measurement is less time consuming,requires simple tools,provides accurate results,and is less influenced by human factors.In this study,24 soybean varieties,such as‘Qiandou 3’,‘Chuandou 16’and‘Daheidou’,were used for assessment.Different methods,including visual estimation,field line transect method and photo line transect method,were used to estimate soybean vegetation coverage and identify one with the maximum accuracy and applicability,using the measured values of the photography method as the reference.The results showed that visual estimation produced the largest error in vegetation coverage measurement,with an average of 7.8%.The error increased first and then decreased with the increase of plant height.The field line transect method displayed higher accuracy,the error was less than 3%(2.8%),but it took the longest time of 6.2 min for a 1 m×1 m quadrat.The error of the photo line transect method was less than 3%,and it consumed less time for field sampling;processing the photos of each quadrat took only 3min.Compared with visual estimation,the photo line transect method showed higher measurement accuracy.Besides,it saved the sampling time and improved work efficiency compared with the field line transect method.Therefore,the present study proposed the photo line transect method as the ideal method for vegetation coverage measurement of soybean and similar plant species.Two line-transects(the total length of the line transect was 2.8 m)via this method could meet the accuracy requirements,with an error of less than 5%.However,the applicability of the photo line transect method in measuring the coverage of other crops should be further explored.