Artificial modification on lateral hydrological connectivity promotes range expansion of invasive Spartina alterniflora in salt marshes of the Yellow River delta, China

Abstract

‘Invasibility’, or the extent to which a habitat is prone to being invaded by plants, is a measure of the resistance of that ecosystem to biological invasion: a limited extent represents abiotic conditions unsuitable for invasion by invasive species; however, human activity can change that and make a habitat prone to rapid invasion. Field surveys and greenhouse experiments were carried out to explore, using spatial analysis, how a strong invader, namely Spartina alterniflora, is assisted by such activities as constructing levees and digging trenches, ditches, and pits in a tidal salt marsh. These activities changed the lateral hydrological connectivity of a salt marsh. The invasibility was then estimated based on the probability of seed dispersal and retention using the classical probabilistic method, and the rate of seedling emergence using threshold analysis. Changes in lateral hydrological connectivity led to more seeds of the invading species being retained, especially in high marshes, and promoted the emergence of its seedlings by making the soil more moist and less saline. The results suggest that changes in the lateral hydrological connectivity in a salt marsh can make it more prone to being invaded. The results have important implications for the control of invasive plants by limiting human activity and thereby regulating lateral hydrological connectivity in coastal ecosystems.