Calculation method of submerged plant biomass in small and medium urban rivers: Based on the investigation and analysis of Shanghai City

Abstract

沉水植物的盖度和生物量是衡量浅水系统恢复程度的重要指标，但城市河道沉水植物的生境由于人为干扰及修复过程，具有较高的异质性，使得城市河道沉水植物盖度和生物量测定更加困难，目前尚无准确、快速的计算方法.本研究以上海市内中小河道为研究对象，通过实测4条河道330余个代表样方的沉水植物生物，研究了基于采样次数的沉水植物单位面积生物量计算方法、采样布点方法和河道总盖度测算方法.结果显示：（1）至少需30~35次面积为0.04 m²的采样可准确估算上海中小河道内沉水植物单位面积的生物量；（2）样点设置可选用随机或等距设置；（3）利用Rededge-M多光谱相机对河道拍摄5波段影像，并进行5~8次重复处理，可较为准确获得整条河道沉水植物盖度.本研究可为城市中小河道沉水植被恢复、河道的分类管理与保护提供参考及依据.;The coverage and biomass of submerged plants are the key indicators of the restoration level of shallow water systems. But the habitat of submerged plants in urban rivers usually has high heterogeneity because of the human disturbance and restoration process. This makes it more difficult to determine the coverage and biomass of submerged plants in urban rivers and lacks an accurate and fast method. In this study, we measured the biomasses of submerged plants in more than 330 representative plots in 4 rivers to investigate the method of calculating the biomass per unit area of submerged plants using the numbers of samplings, as well as the methods of sampling and calculation of total coverage of submerged plants in rivers. The results showed that:(1) At least 30 to 35 samplings (0.04 m²) are required to accurately estimate the biomass per unit area of submerged plants in small and medium rivers in Shanghai; (2) Random or equidistant setting can be selected for sample setting; (3) Getting the band-5 images of the river channels using the Rededge-M multi-spectral camera image and repeating the process for 5 to 8 times, the coverage of submerged plants in the rivers can be obtained with higher accuracy. This study provides crucial reference and knowledge for the restoration of submerged vegetation in small and medium urban rivers and the management and protection of rivers.