Effects of South-to-North Water Diversion Project Cascade Dams on Riparian Vegetation Along the Middle and Lower Reaches of the Hanjiang River, China.

Jiao Yang,Ying Xia,Rui Zhou,En-Hua Li,Chao Yang

doi:10.3389/fpls.2022.849010

Abstract

The influence of the construction of dams for water diversion on the ecological environment has attracted recent widespread attention. Over time, dams have emerged as one of the most important factors affecting the vegetation along the riparian zones of rivers. To elucidate the effects of cascade dams on riparian vegetation along the middle and lower reaches of the Hanjiang River, we examined riparian vegetation types upstream and downstream from dams. A total of 14 sample sites and 131 quadrats perpendicular to the river were investigated in June 2019, and 14 sample sites and 134 quadrats were investigated in October 2019. The riparian vegetation was divided into 15 (in June) and 11 (in October) vegetation types by two-way indicator species analysis (TWINSPAN). Significant differences were found between the vegetation types upstream and downstream of dams. Redundancy analysis (RDA) showed that soil moisture content, distance from the water, altitude and soil total nitrogen (TN) were the main environmental factors affecting plants distributions, and soil moisture content was the main factor affecting the zonal distribution of vegetation. By analyzing the impact of cascade dams on the hydrological regime, we found that the construction of cascade dams led to the differentiation of vegetation types upstream and downstream of the dam, and the riparian habitats were fragmented by these dams. This study provides both an important reference for the protection of riparian vegetation and riparian ecosystems and a basis for the management and restoration of river ecosystems after the construction of cascade dams.

Highlights

Riparian ecosystems are the transition zones from aquatic ecosystem to terrestrial ecosystems and one of the most diverse, rapidly changing and complex habitats on earth (Naiman and Décamps, 1997; Chen et al, 2020)
Vegetation Type Classification In June and October, 110 species belonging to 94 genera and 43 families and 120 species belonging to 99 genera and 44 families, respectively, were found in the middle and lower reaches of the Hanjiang River
In June, the first transect near the water was mainly comprised of communities of Polygon fugax, Paspalum distichum, Typha angustifolia, Cynodon dactylon, Phalaris arundinacea, and Erigeron canadensis in the middle and lower reaches of the Hanjiang River

Summary

Introduction

Riparian ecosystems are the transition zones from aquatic ecosystem to terrestrial ecosystems and one of the most diverse, rapidly changing and complex habitats on earth (Naiman and Décamps, 1997; Chen et al, 2020). Riparian vegetation is an important component of riparian ecosystems (Stromberg, 2001). Riparian vegetation is the primary producer in a riparian ecosystem and plays important functions in energy flow, information flow and biological flow between aquatic and Cascade Dams, Effects, Riparian Vegetation terrestrial ecosystems (Artini et al, 2021). Natural flow variability is the primary driver of riverine ecosystem functions and structures (Wang et al, 2015). Natural disturbances, such as floods and droughts, are integral components of riparian ecosystems (Lytle and Poff, 2004; Rivaes et al, 2017). River water transmission has a positive effect on the migration of vegetation communities along river bank zones, and vegetation responds to climate change and land use changes through river water migration (Nilsson et al, 2010)

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