Global Research on Riparian Zones in the XXI Century: a Bibliometric Analysis

water Review Global Research on Riparian Zones in the XXI Century: A Bibliometric Analysis Sara Pedraza 1, Nicola Clerici 1,* , Jennifer D. Zuluaga Gaviria 2 and Adriana Sanchez 1 1 Department of Biology, Faculty of Natural Sciences, Universidad del Rosario, Kr 26 No 63B-48, Bogotá D.C. 111221, Colombia; [email protected] (S.P.); [email protected] (A.S.) 2 Centro de Recursos para el Aprendizaje y la Investigación, Calle 12C Nº 6-25, Bogotá D.C. 111711, Colombia; [email protected] * Correspondence: [email protected] Abstract: Riparian zones (RZs) are transitional environments at the interface between land and freshwater ecosystems, which are important in terms of socioecological services. In this work, we report a bibliometric-based analysis to unveil the knowledge structure and actors of scientific production on riparian zones for the first 20 years of the 21st century. We performed a literature search, querying for riparian zones publications for the period 2001–2020. The selected 1171 bibliographic records were analyzed by extracting several bibliometric indices of reporting tendencies, location, collaboration dynamics, and top topics. Results show that RZs publications increased considerably from 2001 to 2020, and top journals publishing on the subject are from the water, environmental management, and ecology areas. The US, China, Brazil, and Canada were the most productive countries, while the institutions with higher productivity were the Chinese Academy of Sciences and Oregon University. In terms of impact, the US, Canada, and Australia led in citation number, while the country collaboration network showed that the strongest links occur between China and the US. Our results also show that few studies were produced in low-middle income countries, which Citation: Pedraza, S.; Clerici, N.; suggests a need to funnel international funding to study riparian environments in these geographical Zuluaga Gaviria, J.D.; Sanchez, A. contexts. According to analysis of frequency, top topics are related to water quality and focused on Global Research on Riparian Zones in lotic environments. We here present the main knowledge structure of RZs studies globally for the the XXI Century: A Bibliometric first 20 years of the XXI century. Analysis. Water 2021, 13, 1836. https://doi.org/10.3390/w13131836 Keywords: riparian zones; bibliometric analysis; bibliometrix; Scopus® Academic Editor: Eva Papastergiadou Received: 13 May 2021 1. Introduction Accepted: 24 June 2021 Published: 30 June 2021 Riparian zones (RZs) are transitional environments occurring at the interface between land and freshwater ecosystems, with distinctive biotic and abiotic characteristics strongly Publisher’s Note: MDPI stays neutral regulated by water presence [1–3]. Such environments include floodplains and near-slope with regard to jurisdictional claims in zones ecologically connected to the waterbody by surface and subsurface hydrology [4]. published maps and institutional affil- Riparian areas can develop adjacent to perennial, intermittent, and ephemeral streams, iations. lentic ecosystems, and estuarine-marine shorelines, and their physical and ecological structure is largely regulated by seasonal waterflow dynamics and transport of sediments [5]. Vegetation along lotic ecosystems affects and responds to river processes by modifying water flow, retaining sediments, and modifying erosion susceptibility and morphology of stream banks through flow-vegetation-sediments feedback mechanisms [6]. Riparian trees’ Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. growth rate influences river corridors dynamics and morphology [7,8], and the diversity This article is an open access article and productivity of riparian vegetation can also have large effects on riverine biogeochem- distributed under the terms and ical processes [9]. At the same time, riparian vegetation displays a range of life history, conditions of the Creative Commons morphological, and phenological adaptations as a result of different flow regimes, which Attribution (CC BY) license (https:// derive into distinct traits and strategies for survival, dispersal, and reproduction [10,11]. creativecommons.org/licenses/by/ Anthropic drivers of change, e.g., land use activities, strongly influence their abiotic and 4.0/). biotic structure [12]. Water 2021, 13, 1836. https://doi.org/10.3390/w13131836 https://www.mdpi.com/journal/water Water 2021, 13, 1836 2 of 15 Water 2021, 13, 1836 2 of 14 reproduction [10,11]. Anthropic drivers of change, e.g., land use activities, strongly influence their abiotic and biotic structure [12]. ComprehensiveComprehensive discussionsdiscussions ofof thethe heterogeneousheterogeneous definitionsdefinitions ofof ‘riparian‘riparian zones’zones’ areare providedprovided by Dufour et et al. al. (2019) (2019) [13] [13 and] and Fischer Fischer et etal. al.(2011) (2011) [14]. [14 The]. Thediversity diversity and andcon- confusionfusion of terms of terms present present in the in theliterature literature is also isalso reflected reflected into intothe different the different attempts attempts to spa- to spatiallytially delineate delineate and and map map RZs. RZs. Simple Simple approaches approaches rely relyon the on delineation the delineation of a offixed a fixed or var- or variableiable width width buffer buffer from from the thewater water stream stream bank bank (e.g., (e.g., 1 km 1 [15]). km [15 More]). More complex complex modelling mod- ellingconsiders considers a variety a variety of information of information from fromEarth Earth Observation-based Observation-based geomorphological, geomorphological, hy- hydrological,drological, land land cover-land cover-land use, use, and and vegetation vegetation indices indices [16–18], [16– 18including], including functional functional con- considerationssiderations [19,20]. [19,20 A]. schematic A schematic representation representation of riparian of riparian zones zones is shown is shown in Figure in Figure 1. 1. FigureFigure 1.1. SchematicSchematic representationrepresentation ofof riparianriparian zoneszones andand majormajor ecologicalecological functions.functions. DespiteDespite thethe heterogeneityheterogeneity inin conceptsconcepts andand spatialspatial delineationdelineation approaches,approaches, aa largelarge agreementagreement isis foundfound with with respect respect to to the the high high significance significance of riparianof riparian systems systems in terms in terms of the of multiplethe multiple socioecological socioecological services services they they deliver deliver to society, to society, i.e., i.e., RZs, RZs, and and especially especially riparian ripar- vegetation,ian vegetation, are sourcesare sources of a largeof a large array array of different of different ecosystem ecosystem services services (ESS [21 (ESS]). In [21]). terms In ofterms provisioning of provisioning services, services, fuel and fuel energy and energy can be can obtained be obtained from riparian from riparian forests forests and grass and vegetationgrass vegetation [22,23], [22,23], and they and can they also can be providersalso be providers of important of important genetic resources genetic resources [24]. Sev- eral[24]. regulation Several regulation services are services modulated are modulate by ripariand by zones, riparian such zones, as water such quality as water regulation quality byregulation filtration by of filtration pollutants of pollutants and sediments and sediments [25,26], carbon [25,26], sequestration carbon sequestration and regulation and reg- of micro-climateulation of micro-climate [27,28], pollination [27,28], pollination [29], habitat [29], maintenance habitat maintenance [30], and flow [30], regulation and flow andreg- erosionulation controland erosion [31,32 control]. Riparian [31,32]. areas Riparian also provide areas cultural also provide services, cultural such as services, environmental such as education,environmental aesthetic, education, and recreationalaesthetic, and opportunities recreational opportunities [33,34]. The provision[33,34]. The of provision riparian ESSof riparian is under ESS threat is under due to threat severe due anthropogenic to severe anthropogenic impacts, especially impacts, those especially related those to land re- conversion to agriculture, the alteration of stream flows, water nutrient enrichment, and lated to land conversion to agriculture, the alteration of stream flows, water nutrient en- climate change [35,36]. richment, and climate change [35,36]. Riparian zones are a growing field of research due to their ecological and societal Riparian zones are a growing field of research due to their ecological and societal importance. Several reviews have recently summarized and discussed the scientific lit- importance. Several reviews have recently summarized and discussed the scientific liter- erature on riparian vegetation [6,10,13] and their services [30], riparian biogeochemistry ature on riparian vegetation [6,10,13] and their services [30], riparian biogeochemistry and and contaminants abatement [37], functional riparian buffers delineation [38], riparian contaminants abatement [37], functional riparian buffers delineation [38], riparian struc- structure’s influence on invertebrate ecology [39], and the evolution of research themes ture’s influence on invertebrate ecology [39], and the evolution of research themes linked linked to riparian zones [40]. to riparian zones [40]. Nevertheless, there is still a lack of comprehensive

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