Vegetation Response to Groundwater Variation in Arid Environments: Visualization of Research Evolution, Synthesis of Response Types, and Estimation of Groundwater Threshold.

Feng Huang,Danrong Zhang,Xi Chen

doi:10.3390/ijerph16101849

Abstract

Groundwater depth is an important environmental factor affecting vegetation growth and landscape dynamics in arid environments. This study applied a science mapping approach to visualize the development of groundwater-vegetation-related research, synthesized the vegetation response to changes in groundwater depth, and analyzed the change rate of the response curve to identify the groundwater threshold that is essential to conserve the groundwater-dependent terrestrial ecosystems. These ecosystems emerged as a research hotspot due to climate change, groundwater overexploitation, and the recognition of these ecosystems’ importance for sustainable development. There are two main types of response functions of vegetation to changes in groundwater depth—monotone and bell-shaped functions—among which the monotone function includes linear, curvilinear, and stepwise response. The shape of a response curve is mainly determined by the combined effects of oxygen stress, salinization, and water stress; oxygen stress and salinization dominate in shallow groundwater depth, while water stress dominates in deep groundwater depth. On a non-linear vegetation metric—groundwater depth response curve, the change rate analysis method is effective to identify the breakpoint that can be taken as a candidate threshold of groundwater depth. The results will add insight into the intellectual structure of the groundwater-vegetation interactions and provide practical reference for groundwater resource management, ecological conservation, and sustainable development in arid environments.

Highlights

Arid environments that can be delineated as semi-arid, arid, and hyper-arid zones cover approximately one-third of the Earth’s land surface [1]
This study focuses on the groundwater-vegetation interactions in arid environments and aims to (a) provide a visual analysis of research development in the past two decades with particular focus on the latest research; (b) review the literature of case studies and assemble the relationships reported in these disparate studies to determine if any generalized pattern can be extracted between vegetation and groundwater variation, i.e., changes in the depth to groundwater table; and (c) based on the synthesized patterns, discuss a change rate analysis of response curve to detect the groundwater threshold that is essential for the health of the groundwater-dependent terrestrial ecosystems (GDTEs)
The groundwater-dependent ecosystems (GDEs) that are important elements of biodiversity provide valuable goods and services to human society [34]. They can be located in marine, coastal, riparian, in-stream, terrestrial, and in cave and aquifer environments, among which the GDTEs are mostly pertinent with the groundwater-vegetation interactions in arid environments [3]

Summary

Introduction

Arid environments that can be delineated as semi-arid, arid, and hyper-arid zones cover approximately one-third of the Earth’s land surface [1]. Regions with arid environments are home to over 38% of the world’s population; withdrawals of groundwater for increasing population numbers, along with expanding agricultural and domestic use, cause groundwater decline and severely limit the water availability for groundwater-dependent terrestrial ecosystems (GDTEs) [4]. This results in loss of biodiversity, ecological degradation, land desertification, and environmental deterioration, which in turn negatively affect the social and economic development [5].

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Results

Discussion

Conclusion