How Does Spartina alterniflora Invade in Salt Marsh in Relation to Tidal Channel Networks? Patterns and Processes

Limin Sun,Xu Ma,Dongdong Shao,Zhonghua Ning,Baoshan Cui,Weilun Gao,Tian Xie

doi:10.3390/rs12182983

Abstract

Rapid invasion of Spartina alterniflora in coastal wetlands throughout the world has attracted much attention. Some field and imagery evidence has shown that the landward invasion of S. alterniflora follows the tidal channel networks as the main pathway. However, the specific patterns and processes of its invasion in salt marshes in relation to tidal channel networks are still unclear. Based on yearly satellite images from 2010 to 2018, we studied the patterning relationship between tidal channel networks and the invasion of S. alterniflora at the south bank of the Yellow River Estuary (SBYRE). At the landscape (watershed and cross-watershed) scale, we analyzed the correlation between proxies of tidal channel network drainage efficiency (unchanneled flow lengths (UFL), overmarsh path length (OPL), and tidal channels density (TCD)) and spatial distribution of S. alterniflora. At the local (channel) scale, we examined the area and number of patches of S. alterniflora in different distance buffer zones outward from the tidal channels. Our results showed that, overall, the invasion of S. alterniflora had a strong association with tidal channel networks. Watershed with higher drainage efficiency (smaller OPL) attained larger S. alterniflora area, and higher-order (third-order and above) channels tended to be the main pathway of S. alterniflora invasion. At the local scale, the total area of S. alterniflora in each distance buffer zones increased with distance within 15 m from the tidal channels, whereas the number of patches decreased with distance as expansion stabilized. Overall, the S. alterniflora area within 30 m from the tidal channels remained approximately 14% of its entire distribution throughout the invasion. The results implicated that early control of S. alterniflora invasion should pay close attention to higher-order tidal channels as the main pathway

Highlights

Over the last decades, perennial rhizomatous Spartina alterniflora, as a dreaded invader spreading rapidly to estuaries and coastal salt marshes throughout the world, has received much attention [1,2,3]
We explore the effects of tidal channel networks on the spatiotemporal invasion dynamics and distribution patterns of S. alterniflora at both local and landscape scales at a typical coastal salt marsh at the Yellow River Estuary (YRE), China
To further characterize the spatiotemporal pattern of S. alterniflora invasion in relation to distance from tidal channel networks at the local scales, we examined the areas occupied by S. alterniflora from 2014 to 2018 using high-resolution GaoFen images, given that both the evolution of tidal channels and invasion rate of S. alterniflora gradually stabilized after 2014

Summary

Introduction

Perennial rhizomatous Spartina alterniflora, as a dreaded invader spreading rapidly to estuaries and coastal salt marshes throughout the world, has received much attention [1,2,3]. The invasion of S. alterniflora is influenced by numerous biotic and abiotic factors, such as nutrients [7] and herbivores [8], as well as local geomorphology [9,10] and hydrology [11,12], which can be further linked to tidal channels as ubiquitous landscape configuration controlling tidal prism and inundation, fluxes of sediments, nutrients, and hydrochorous seed dispersal in and between salt marshes [13,14,15] The latter can be of disproportionate importance by mediating colonization of remote habitats [16,17]. To make a robust prediction of S. alterniflora invasion for coastal wetland management, it is important to improve our understanding of the role of tidal channel networks in its invasion in coastal salt marshes

Methods

Results

Conclusion