Ecological Indicators (Oct 2023)

Long-term monitoring and phenological analysis of submerged aquatic vegetation in a shallow lake using time-series imagery

  • Yingcong Wang,
  • Zhaoning Gong,
  • Han Zhou

Journal volume & issue
Vol. 154
p. 110646

Abstract

Read online

Submerged aquatic vegetation (SAV) is a key functional group for the restoration of wetlands and aquatic ecosystems. It plays a vital role in the stability of ecosystem structure and function in shallow lakes and reservoirs. With Baiyangdian Lake as the research area, Landsat TM/ETM+/OLI and Sentinel-2 imagery datasets were used to explore the phenological characteristics of SAV over different time scales and construct a phenological map of the SAV groups. The long-term spatial distribution characteristics and trends of SAV from 1986 to 2021 were analyzed. The results show the following: (1) the harmonic analysis of time series (HANTS) eliminated abnormal observations and noise. Normalized difference vegetation index (NDVI) time series curves generated after HANTS accurately reflected the phenological characteristics of SAV. The early spring submerged aquatic vegetation (SAV1), such as Potamogeton crispus, entered the germination period in late February at the earliest (DOY = 53). The mature period ran from April to May, after which SAV1 began to decline gradually. The length of the growing season (LOS) was about 110 days. SAV2, which was represented by Ceratophyllum demersum, Myriophyllum verticillatum, and Potamogeton pectinatus, germinated in early April (DOY = 99). The mature period ran from July to September. The length of the growing season was 210 days. (2) The decision tree constructed based on the NDVI and modified normalized difference water index (MNDWI) identified SAV with an accuracy of 89.7%. (3) The distribution range of the SAV changed dramatically during 1986–2021. According to the area change, it can be divided into a shrinkage period, expansion period, degeneration period, and initial period of recovery. The succession trend of SAV provide a theoretical scientific basis and technical support for the ecological restoration and management of shallow lake ecosystems.

Keywords