The importance of structural and functional characteristics of tidal channels to smooth cordgrass invasion in the Yellow River Delta, China: Implications for coastal wetland management

Abstract

Understanding the spatiotemporal landscape dynamics and spread pathways of invasive plants, as well as their interactions with geomorphic landscape features, are of great importance for predicting and managing their future range-expansion in non-native habitats. Although previous studies have linked geomorphic landscape features such as tidal channels to plant invasions, the potential mechanisms and critical characteristics of tidal channels that affect the landward invasion by Spartina alterniflora, an aggressive plant in global coastal wetlands, remain unclear. Here, using high-resolution remote-sensing images of the Yellow River Delta from 2013 to 2020, we first quantified the evolution of tidal channel networks by analyzing the spatiotemporal dynamics of their structural and functional characteristics. The invasion patterns and pathways of S. alterniflora were then identified. Based on the above-mentioned quantification and identification, we finally quantified the influences of tidal channel characteristics on S. alterniflora invasion. The results showed that tidal channel networks presented increasing growth and development over time, and their spatial structure evolved from simple to complex. The external isolated expansion of S. alterniflora played a dominant role during the initial invasion stage, and then they connected the discrete patches into the meadow through marginal expansion. Afterwards, tidal channel-driven expansion gradually increased and became the primary way during the late invasion stage, accounting for about 47.3%. Notably, tidal channel networks with higher drainage efficiency (shorter OPL, higher D and E) attained larger invasion areas. The longer the tidal channels and the more sinuous the channel structure, the greater the invasion potential by S. alterniflora. These findings highlight the importance of structural and functional properties of tidal channel networks in driving plant invasion landward, which should be incorporated into future control and management of invasive plants in coastal wetlands.