兴化市河网水葫芦信息时空动态变化研究

Study on the spatio-temporal dynamics of water hyacinth information in the river network of Xinghua city

水葫芦作为我国十大入侵植物之一,有着极强的繁殖能力,其在平原水网地区已泛滥成灾,严重影响水生生态及河道行洪安全。本文以兴化市为例,基于2017—2021年Sentinel-2影像,通过支持向量机算法自动提取河网水葫芦分布,计算兴化市59条主要河流水葫芦平均覆盖度,建立水葫芦暴发情况等级分类方法,并对兴化市水葫芦覆盖区的NDVI值进行时空异质性探测。试验结果表明,2017—2021年,水葫芦面积占比在0.05~0.2,最低值为0.084,最高值为0.176;按暴发等级划分有重度暴发河流9条、中度暴发河流34条、轻度暴发河流16条;时空异质性探测指标总体呈现上升趋势,且在2020年下半年达到峰值1.025。通过时空异质性探测水葫芦时空变化情况,可为水葫芦的暴发监测与合理防治提供科学依据。

As one of the top ten invasive plants in China,water hyacinth has a strong reproduction ability,and it has flooded in plain river network,seriously affecting the aquatic ecology and river flooding safety.In this paper,taking Xinghua city as an example,based on Sentinel-2 images from 2017 to 2021,the distribution of water hyacinth in the river network is automatically extracted by the support vector machine algorithm,the average coverage of water hyacinth in 59 major rivers in Xinghua city is computed,a hierarchical classification method for water hyacinth outbreaks is established,and the spatio-temporal heterogeneity of NDVI values in the water hyacinth coverage area of Xinghua city is detected.The experimental results show that between 2017 and 2021,the percentage of water hyacinth area ranged from 0.05 to 0.2,with the lowest value of 0.084 and the highest value of 0.176;there are 9 rivers with severe outbreaks,34 rivers with moderate outbreaks,and 16 rivers with mild outbreaks according to the outbreak class;and the spatio-temporal heterogeneity detection indexes showed a general upward trend,and reached a peak value of 1.025 in the second half of 2020.Detecting the spatio-temporal changes of water hyacinth through spatio-temporal heterogeneity can provide a scientific basis for monitoring and rational control of water hyacinth outbreaks.