Recent decade expansion of aquatic vegetation covering in china's lakes

Abstract

Often characterized as “sentinels of lake aquatic ecosystems”, different life-form aquatic vegetation covering dynamics reflects both short- and long-term climate fluctuations and human activities. Previous assessments often lack comprehensive spatiotemporal coverage of aquatic vegetation dynamics, prompting a deeper understanding of aquatic vegetation variations and underlying drivers of such change. This article first presents a dataset of semi-decadal-scale trends in aquatic vegetation covering of 616 China’s lakes (>10 km2) from 1986 to 2020, after validating a machine learning method of random forest (RF) by field investigations and literature reviews. The total area of aquatic vegetation in lakes nationwide was varied from 10,345.40 km2 to 17,329.31 km2 (a 67.51 % increase) since 1986, with a growth rate of 169.85 km2/yr. As of 2020, the aquatic vegetation is mainly concentrated in Tibetan Plateau Lake Zone (TPL) (55.99 %) and Eastern Plain Lake Zone (EPL) (25.86 %), followed by other regions. It was identified the changes in aquatic vegetation area experienced three periods: moderate growth (1986–1999), slight losses (2000–2010), and marked recovery (2011–2020). Specifically, the TPL experienced the most remarkable expansion, primarily contrbution from submerged aquatic vegetation (SAV). It is found that smaller lakes in plain area are more conducive to the growth of aquatic vegetation, as shown by the increase in the percentage of aquatic vegetation area (PAV) with the decrease in lake size. But the lakes in TPL showed after 2010 larger lakes are more advantageous in aquatic vegetation recovery, attributing to climate-induced lake expansion. Furthermore, lakes with more intricately shapes also exhibited relative advantages in aquatic vegetation expansion. Geographic and climatic factors also played a pivotal role, with altitude notably influencing temperature and precipitation, thus exerting a considerable impact on aquatic vegetation growth. This study have estimated the semi-decade dynamic characteristics of aquatic vegetation in lakes across China since 1986, concluded that aquatic vegetation ushered in a vigorous recovery period around 2010, offering compelling evidence for the increasing greening trend of aquatic ecosystems.

Keywords

• Aquatic vegetation
• Google earth engine
• Spatiotemporal changes
• Satellite data
• China’s lakes