This article was originally published in Encyclopedia of Inland Waters 2nd edition, published by Elsevier, and the attached copy is provided by Elsevier for the author's benefit and for the benefit of the author’s institution, for non-commercial research and educational use, including without limitation, use in instruction at your institution, sending it to specific colleagues who you know, and providing a copy to your institution’s administrator. All other uses, reproduction and distribution, including without limitation, commercial reprints, selling or licensing copies or access, or posting on open internet sites, your personal or institution’s website or repository, are prohibited. For exceptions, permission may be sought for such use through Elsevier's permissions site at: https://www.elsevier.com/about/policies/copyright/permissions Egger Gregory, Rood Stewart B, Becker Isabell, Betz Florian, Chepinoga Victor, Deil Ulrich, Lashchinskiy Nikolay, Magnússon Borgthor, Roth Aglaja, Stewart Glenn, Troeva Elena and Müller Norbert. (2022) Riparian Vegetation of Gravel-bed Rivers—A Global Review. In: Mehner, Thomas and Tockner, Klement, Encyclopedia of Inland Waters 2nd edition. vol. 3, pp. 182-213. Oxford: Elsevier. dx.doi.org/10.1016/B978-0-12-819166-8.00173-0 © 2022 Elsevier Ltd. All rights reserved. Author's personal copy Riparian Vegetation of Gravel-bed Rivers—A Global Review Gregory Eggera,b, Stewart B Roodc, Isabell Beckerb, Florian Betzd, Victor Chepinogae,f, Ulrich Deilg, Nikolay Lashchinskiye, Borgthor Magnússonh, Aglaja Rothb, Glenn Stewarti, Elena Troevaj, and Norbert Müllerk, aUniversity of Natural Resources and Life Sciences Vienna, Institute of Hydrobiology and Aquatic Ecosystem Management, Vienna, Austria; bKarlsruhe Institute of Technology, Institute of Geography and Geoecology, Karlsruhe, Germany; cDepartment of Biological Sciences, University of Lethbridge, Lethbridge, AB, Canada; d Catholic University Eichstaett-Ingolstadt, Applied Physical Geography, Eichstätt, Germany; eCentral Siberian Botanical Garden SB RAS, Novosibirsk, Russia; fDepartment of Botany, Irkutsk State University, Irkutsk, Russia; gFaculty of Biology, Department of Geobotany, University of Freiburg, Freiburg, Germany; hIcelandic Institute of Natural History, Garðabær, Iceland; iLincoln University, Christchurch, New Zealand; j Institute for Biological Problems of Cryolithozone SB RAS, Yakutsk, Russia; kDepartment of Landscape Management & Restoration Ecology, University of Applied Sciences Erfurt, Erfurt, Germany © 2022 Elsevier Inc. All rights reserved. This article was reviewed for the Encyclopedia of Inland Waters, Second Edition by Section Editors Wolfgang Junk and Florian Wittmann. Introduction Mountain ranges Reference regions and their riparian vegetation Glacier Forelands of the Arctic Tundra, Iceland South Central Alaska Region, Alaskan Taiga Canadian Rocky Mountains Northeast Siberian Mountains, Russian Taiga Hindu Kusch-Karakorum-Himalaya-Region, Central Asia Alps, Europe Wadis in the Mountain Ranges of the Middle East Southern Alps, New Zealand Southern Andes, Patagonia Conclusion and synthesis References Further reading 183 183 184 187 192 194 196 198 201 203 205 207 210 211 213 Glossary Alluvial river Self formed river in which the bed and banks are made up of mobile sediment. Azonal vegetation Plant communities that depend on local extraordinary habitat characteristics e.g., microclimate, inundation, see also zonal vegetation. Boreal zone Regions of the northern hemisphere with cold temperatures approximately between 50 to 70 N latitude. Braided rivers Rivers characterized by mobile, multi-thread channels within gravel or sand-dominated fluvial corridors. Ecological niche The match of a species to a specific environmental condition. Endemic The state of a species being native to a single defined geographic location. Floodplain Flat land area adjacent to a stream which is within the influence of the hydromorphodynamics of the river. Fluvial Processes and landforms created by the flowing water. Glacier fore-fields The region between the current front of the glacier and the moraines of the latest maximum. Gravel-bed rivers Coarse-grained alluvial rivers which are particularly characterized by dynamic fluvial processes that constantly change and renew the surface and subsurface of the river’s valley floor. Last glacial maximum The LGM was the most recent time during the Last Glacial Period where the ice sheets were at their greatest extent. Phreatophytes Deep-rooted plants that obtain a significant portion of the water that it needs from the phreatic zone (zone of saturation) or the capillary fringe above the phreatic zone. Riparian vegetation Plant communities of floodplains (synonym floodplain vegetation). Riverine Processes, landforms or species relating to or produced by a river. Shear stress The external force acting on an object or surface parallel to the slope. Taiga The boreal forest throughout the high northern latitudes, between the tundra and the temperate forest, from about 50 N to 70 N. Trait Any morphological, physiological or phenological feature measurable at the individual level of a species. Tundra Open, treeless landscape (mostly) over permafrost soils of the subpolar climate zone. Wetland ecosystems Comprise areas that transition between terrestrial (land) areas and aquatic (water) areas. Zonal vegetation Plant communities that depend on the large-scale habitat characteristics of the macro climate—see also azonal vegetation. 182 Encyclopedia of Inland Waters, 2nd edition Encyclopedia of Inland Waters, (2022) https://doi.org/10.1016/B978-0-12-819166-8.00173-0 Author's personal copy STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers 183 Introduction Gravel-bed rivers and particularly braided rivers represent extraordinary wetland ecosystems due to their high disturbance regimes (Bornette and Amoros, 1996; Müller, 1998; Plachter and Reich, 1998). In contrast to groundwater- and flood-dominated wetlands, the main ecological factor is the geomorphological dynamics (Piégay et al., 2006). Their disturbance-adapted characteristic plant species create distinctive azonal vegetation types, contrary to the large-scale zonal vegetation in the surrounding areas (Fig. 1). Consequently, under natural conditions they contribute significantly to global biodiversity (Tockner et al., 2006). However, due to the worldwide human impacts in the hydrological and sediment regimes by dams, diversions, flood control and river regulation (Hauer et al., 2016; Hohensinner et al., 2021) their characteristic native species have become extirpated along many river corridors (e.g., Müller, 1995; Tockner et al., 2008). Another threat to their biodiversity is their vulnerability to invasion of non-native plant species because the braided river floodplains provide regularly open sites for seedling colonization and the rivers serve as seed dispersal pathways (Liendo et al., 2015). There have been many case studies of riparian vegetation existing in single mountain ranges (e.g., for Asia, Africa, Europe, Asia), but overviews of larger mountain regions similar to the analyses of the European Alps (Egger et al., 2019a,b; Kalníková et al., 2021) are lacking. With this chapter we provide a global review of the riparian vegetation of gravel-bed rivers in mountain ranges, focusing on two questions: - Which native plants are characteristic and abundant in the different successional phases of the riparian vegetation? - Which invasive non-native plants are frequent within the riparian vegetation communities? Mountain ranges Mountain ranges of similar climatic conditions with frequent occurrences of gravel-bed rivers and including a high proportion of braided rivers were grouped into nine reference regions using data of ESRI (2010, 2016) and Natural Earth (2018) (Figs. 2 and 3). Based on the data of Maier et al. (2022) the reference regions were selected to cover a wide range of abiotic factors. This includes their location on different continents of both hemispheres, different altitudes of mountain ranges, and varying percentage of current Fig. 1 Gravel-bed rivers are shaped by high morphodynamics, drought and periodic flooding and are therefore colonized by adapted pioneer plants. This applies in particular to braided rivers like the shown Bush River that drains from the Columbia Icefields of the Canadian Rocky Mountains west. (Photo: S. Rood). Encyclopedia of Inland Waters, (2022) Author's personal copy 184 STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers Fig. 2 Main global mountain ranges (grey) and reference regions with high proportions of braided rivers (described in chapters 4–12). and historical glaciation. Climatic factors range from tropical to boreal and arctic climates, resulting in different floristic regions that influence riparian vegetation communities. Additionally, different extents of human impacts and land use intensities were considered. The reference regions include different numbers of regional mountain ranges, ranging from one main range such as the Patagonian Andes to several mountain ranges that occur in Central Asia. Each region is considered as representative of the associated mountain range for analyses of the riparian vegetation characteristics. Reference regions and their riparian vegetation The description of the nine reference regions and of their riparian vegetation, including their native and invasive non-native plant species, is based on published reports and was undertaken in close collaboration with regional experts. Invasive non-native plants (or ‘invasive exotic species’) indicates non-native species which have harmful effects on native biodiversity (CBD, 2010; Richardson et al., 2000). Plant species names were assigned according to Taxonomic Name Resolution Service (Boyle et al., 2013). Commencing each subchapter, a short geographical introduction is provided using data from Linke et al. (2019), Masutomi et al. (2009), and RGI Consortium (2017). The subsequent description of the riparian vegetation is focused on the characteristic and frequent native and invasive non-native plants. Selected species of the nine reference mountain regions are provided in Table 1, with information about frequency, endemic status, occurrence of main habitat types and succession phase. For the categorization of the riparian vegetation we used the ‘fluvial biogeomorphic succession concept’ proposed by Corenblit et al. (2007, 2011, 2015). Following this concept, river corridors worldwide are characterized by four consecutive succession phases. The concept starts with the initial ‘geomorphic phase’ with large areas of vegetation-free gravel sites, e.g., after total destruction of a site by a flood event. The areas are mainly shaped by the flow regime and the sediment properties (Corenblit et al., 2007). The open sand and gravel bars offer many sites for plant germination, but colonization is aggravated by the strong morphodynamics especially in braided river systems. Pioneer plants can only establish during a suitable window of opportunity (Balke et al., 2014) in the ‘pioneer phase.’ These pioneer plants are still particularly influenced by the hydrogeomorphic processes and require a set of functional traits to cope with the frequent disturbances and stressors in river corridors (Gurnell et al., 2016). In general, key traits relate to plant reproduction, growth and survival (Violle et al., 2007) with adaptive traits along braided rivers to resist strong shear stress, sediment deposition and uprooting (Bornette et al., 2008). Through these specialized adaptations and response traits Encyclopedia of Inland Waters, (2022) Author's personal copy STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers Fig. 3 Exemplary sites of the nine reference mountain ranges with frequent occurrences of braided rivers on the scale of 1:100.000 (ESRI Satellite). Encyclopedia of Inland Waters, (2022) 185 Author's personal copy 186 STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers Fig.3—Cont’d Encyclopedia of Inland Waters, (2022) Author's personal copy STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers 187 Fig.3—Cont’d (Violle et al., 2007), plants increase their resistance (‘maintaining structure’) and resilience (‘restoring structure’) to disturbances (Holling, 1973) and also generate biogeomorphic feedback that reduces morphodynamics. The aboveground biomass modifies the flow field, increases roughness (Bennett et al., 2008; Gurnell, 2014; Gurnell et al., 2016; Liu et al., 2010) and retains sediment (Zong and Nepf, 2010), while the underground biomass reduces the erosion capacity of the land surface and thereby contributes to its stabilization (Gurnell, 2014). These interactions set the ‘biogeomorphic phase’ of succession in motion. Especially colonized sites by ecosystem engineers (Jones et al., 1994) are more resistant to disturbances and destruction due to their enormous effects on the morphodynamics. The final ‘ecologic phase’ is characterized by more stable habitats and autogenic ecological processes. Vegetation is less influenced by the river, succession processes continue and long-lived plant communities begin to establish (Bazzaz, 1979). In the presence of reduced fluvial processes, the late-successional stages transition into the surrounding zonal vegetation. We expanded the ‘ecologic phase’ into an ‘early’ and a ‘late successional phase’. Characteristic trees of the ‘early successional ecologic phase’ establish on open bars, grow rapidly, are shade intolerant, and are well adapted to high hydro-morphodynamics. In contrast, trees of the ‘late successional ecologic phase’ establish on stable sites, are more shade tolerant and grow more slowly (Egger et al., 2019a). Glacier Forelands of the Arctic Tundra, Iceland The reference mountain region of the Arctic Tundra is located in the Vatnajökull mountain range (No. 212; Fig. 2) in south-eastern Iceland. The area is dominated by the Vatnajökull Glacier which currently covers over 80% of the mountain range. The glacier covers almost 7800 km2 and is the largest ice cap of Iceland and outside of the Arctic. About 30 outlet glaciers flow from the ice cap, which reaches over 2000 m in altitude, and end in an extensive moraine landscape in the lowlands and highlands to the north of the glacier. These are closely interwoven with a number of fens of braided rivers, some several km wide, along with alluvial outwash terraces. Numerous large and small glacial rivers fall from the glaciers and the rivers flowing out of the mountain range to the South are mainly sparsely vegetated along their courses (Fig. 4). In general, the mountain range is scarcely forested and anthropogenic impact is very low with a population density of only 0.01 person per km2. The median annual temperature is 0.9 C and precipitation 1.380 mm. The vegetation colonization of the braided river corridors in the glacier fore-fields is determined by a complex interaction of several environmental factors and succession is generally slower in the cooler Artic than in temperate climate regions (Glausen and Tanner, 2019; Vilmundardóttir et al., 2014). Following the glacier’s maximum extent in the last Little Ice Age at the end of the 19th century, the glaciers of Vatnajökull have been continuously receding. The ice-free moraine fields vary in length and are gradually colonized by vegetation during different succession phases. In the area of braided river corridors, primary succession is additionally dominated by the alluvial hydro- and morphodynamics of the glacial streams (Vilmundardóttir et al., 2014). The young alluvial soils are wet to dry, nutrient poor, and characterized by low carbon content. Most areas of these highly dynamic rivers are un-vegetated or sparsely vegetated. Common plants of the ‘pioneer phase’ are Agrostis stolonifera, Festuca richardsonii and sporadically Arabidopsis petraea, Armeria maritima, Carex maritima, Cerastium fontanum, Equisetum arvense, E. variegatum, Juncus arcticus, Rumex acetosella, Silene uniflora and S. acaulis. In addition, there are moss species such as Racomitrium ericoides, which form the largest cover, as well as Drepanocladus aduncus and Philonotis fontana (Magnússon et al., 2016; Vilmundardóttir et al., 2015) (Fig. 5). Flat, sandy floodplains with organic soils are dominated by Juncus arcticus meadows. In addition, Carex nigra, Empetrum nigrum, Salix arctica and S. lanata are predominant (Fig. 6). Further characteristic plants are grasses like Agrostis stolonifera, A. vinealis, Calamagrostis neglecta, Festuca vivipara, Luzula multiflora, Trisetum spicatum and herbs including Bistorta vivipara, Cardamine hirsuta, Epilobium palustre, Equisetum arvense, E. variegatum, Filipendula ulmaria, Galium normanii, G. verum, Leontodon autumnalis, Parnassia palustris, Platanthera hyperborea and Rhinanthus minor (Magnússon et al., 2016). Encyclopedia of Inland Waters, (2022) Author's personal copy 188 STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers Table 1 Selected characteristic native plants (light green ¼ sparse; dark green ¼ abundant) and non-native plants (yellow ¼ sparse; orange ¼ abundant) with information about succession phase (SP: PioPh ¼ Pioneer phase; BiogeoPh ¼ Biogeomorphic phase; ESEPh ¼ Early successional ecologic phase; LSEPh ¼ Late successional ecologic phase); endemic status in the reference regions (ED) and occurrence (OC) of main habitat types (RIP ¼ restricted to riparian habitats; FAC ¼ facultative, in riparian and terrestrial habitats). Plant name SP ED OC Aquilegia parviflora Ledeb. PioPh - FAC Eclipta prostrata (L.) L. PioPh - FAC Impatiens glandulifera Royle PioPh - FAC Lachnagrostis filiformis (G. Forst.) Trin. PioPh - FAC Acaena magellanica Vahl PioPh - FAC Agrostis inconspicua Kunze ex E. Desv. PioPh - FAC Agrostis stolonifera L. PioPh - FAC Arundo donax L. PioPh - RIP Bacopa monnieri (L.) Wettst. PioPh - FAC Calamagrostis pseudophragmites (Haller f.) Koeler PioPh - RIP Delphinium cheilanthum Fisch. ex DC. PioPh - FAC Echium vulgare L. PioPh - FAC Epilobium angustifolium subsp. angustifolium PioPh - FAC Epilobium brunnescens (Cockayne) P.H. Raven & Engelhorn PioPh NZ RIP Epilobium dodonaei Vill. PioPh - RIP Equisetum arvense L. PioPh - FAC Fallopia japonica (Houtt.) Ronse Decr. PioPh - FAC Festuca richardsonii Hook. PioPh - FAC Gunnera magellanica Lam. PioPh - FAC Imperata cylindrica (L.) Raeusch. PioPh - FAC Juncus scheuchzerioides Gaudich. PioPh - FAC Lachnagrostis lyallii (Hook. f.) Zotov PioPh NZ FAC Lupinus nootkatensis Donn ex Sims PioPh - Lupinus polyphyllus Lindl PioPh - RIP Melilotus albus (Medik.) PioPh - FAC Phalaris arundinacea L. PioPh - RIP Phragmites australis (Cav.) Trin. ex Steud. PioPh - FAC Poa novae-zelandiae Hack. PioPh NZ FAC Rytidosperma setifolium (Hook. f.) Connor & Edgar PioPh NZ FAC Saccharum spontaneum L. PioPh - Saxifraga aizoides L. PioPh - RIP Solidago canadensis L. PioPh - FAC Sonchus arvensis L. PioPh - FAC Tanacetum vulgare L. PioPh - FAC Alnus alnobetula (Ehrh.) K. Koch BiogeoPh - FAC Berberis microphylla F. Dietr. BiogeoPh PA FAC Buddleja davidii Franch. BiogeoPh Carmichaelia grandiflora (Benth.) Hook.f. BiogeoPh NZ FAC Carmichaelia nigrans G.Simpson BiogeoPh NZ FAC Coprosma acerosa A. Cunn. BiogeoPh NZ FAC Cornus sericea L. BiogeoPh Discaria toumatou Raoul BiogeoPh NZ FAC Empetrum nigrum L. BiogeoPh Escallonia virgata (Ruiz & Pav.) Pers. BiogeoPh PA FAC Helichrysum depressum (Hook.f.) Benth. & Hook.f. BiogeoPh NZ RIP Muehlenbeckia axillaris (Hook. f.) Endl. BiogeoPh - FAC Myricaria germanica (L.) Desv. BiogeoPh - RIP Myricaria pulcherrima Batalin BiogeoPh AS RIP Salix alaxensis (Andersson) Coville BiogeoPh - FAC Salix arctica Pall. BiogeoPh - FAC Salix arctophila Cockerell ex A. Heller BiogeoPh - FAC Salix bebbiana Sarg. BiogeoPh - RIP Salix brachycarpa Nutt. BiogeoPh - FAC - - IL AT CA RT FAC FAC FAC FAC FAC Encyclopedia of Inland Waters, (2022) AS AL ME NZ PA Author's personal copy STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers Plant name SP ED OC Salix daphnoides Vill. BiogeoPh - RIP Salix drummondiana Barratt ex Hook. BiogeoPh - FAC Salix eleagnos Scop. BiogeoPh - RIP Salix exigua Nutt. BiogeoPh - RIP Salix glauca L. BiogeoPh - FAC Salix herbacea L. BiogeoPh - FAC Salix lanata L. BiogeoPh - FAC Salix lucida Muhl. BiogeoPh - RIP Salix monticola Bebb BiogeoPh - RIP Salix phylicifolia L. BiogeoPh - FAC Salix planifolia Pursh BiogeoPh - FAC Salix purpurea L. BiogeoPh - RIP Tamarix hispida Willd. BiogeoPh AS FAC Tamarix mascatensis Bunge BiogeoPh - FAC Tamarix nilotica (Ehrenb.) Bunge BiogeoPh - FAC Berberis empetrifolia Lam. BiogeoPh - FAC Cytisus scoparius (L.) Link BiogeoPh - FAC Elaeagnus angustifolia L. BiogeoPh - FAC Fuchsia magellanica Lam. BiogeoPh - FAC Gaultheria mucronata (L. f.) Hook. & Arn. BiogeoPh PA FAC Halostachys caspica C.A. Mey. ex Schrenk BiogeoPh AS FAC Hippophae rhamnoides L. BiogeoPh FAC Jatropha pelargoniifolia Courbai BiogeoPh ME FAC Nerium oleander L BiogeoPh - FAC Pinus pumila (Pall.) Regel BiogeoPh - FAC Rhazya stricta Decne. BiogeoPh - FAC Rosa rubiginosa L. BiogeoPh - FAC Tamarix ramosissima Ledeb. BiogeoPh - FAC Ulex europaeus L. BiogeoPh - FAC Betula nana L. ESEPh - FAC Alnus incana (L.) Moench ESEPh - RIP Betula pubescens Ehrh. ESEPh - FAC Chosenia arbutifolia (Pall.) A.K. Skvortsov ESEPh - RIP Populus alba L. ESEPh - RIP Populus balsamifera L. Populus balsamifera ssp. trichocarpa (Torr. & A. Gray ex Hook.) Brayshaw Populus deltoides W. Bartram ex Marshall ESEPh - RIP ESEPh - RIP ESEPh - RIP Populus euphratica Olivier ESEPh - FAC Populus nigra L. ESEPh - RIP Populus pruinosa Schrenk ESEPh AS FAC Populus suaveolens Fisch ESEPh - RIP Populus tremula L. ESEPh - FAC Salix alba L. ESEPh - RIP Salix fragilis L. ESEPh - RIP Salix humboldtiana Willd. ESEPh - RIP Salix rorida Lacksch. ESEPh - FAC Sorbus aucuparia L. ESEPh - FAC Salix babylonica L. ESEPh - RIP Acacia ehrenbergiana Hayne LSEPh - FAC Acer glabrum Pursh LSEPh - FAC Betula pendula Roth LSEPh - FAC Dacrycarpus dacrydioides (A. Rich.) de Laub. LSEPh - FAC Ficus cordata subsp. salicifolia (Vahl) C.C. Berg LSEPh - FAC Ficus vasta Forssk. LSEPh ME FAC Fraxinus excelsior L. LSEPh - Larix cajanderi Mayr LSEPh RT FAC - IL AT CA RT FAC Encyclopedia of Inland Waters, (2022) AS AL ME NZ PA 189 Author's personal copy 190 STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers Plant name SP ED OC Larix gmelinii (Rupr.) Kuzen. LSEPh - FAC Nothofagus antarctica (G. Forst.) Oerst. LSEPh PA FAC Nothofagus betuloides (Mirb.) Oerst. LSEPh PA FAC Nothofagus menziesii (Hook. f.) Oerst LSEPh NZ FAC Nothofagus pumilio (Poepp. & Endl.) Krasser LSEPh PA FAC Quercus robur (Ten.) A. DC. LSEPh - FAC Robinia pseudoacacia L. LSEPh - FAC Salix schwerinii E.L. Wolf LSEPh - RIP Ulmus laevis Pall. LSEPh - RIP Tamarix aphylla (L.) H. Karst. LSEPh - RIP Dacrydium cupressinum Sol. ex G.Forst LSEPh NZ RIP Dicksonia squarrosa (G. Forst.) Sw. LSEPh NZ FAC Luma apiculata (DC.) Burret LSEPh PA RIP Picea abies (L.) Karst. LSEPh - FAC Picea glauca (Moench) Voss LSEPh - FAC Picea mariana (Mill.) Britton, Sterns & Poggenb LSEPh - FAC Picea obovata Ledeb. LSEPh - FAC Pinus sylvestris L. LSEPh - FAC Podocarpus nubigenus Lindl. LSEPh PA FAC Prumnopitys ferruginea (G.Benn. ex D.Don) de Laub. LSEPh NZ FAC Thuja plicata Donn ex D. Don LSEPh - Leiospermum racemosum (L. f.) D. Don LSEPh NZ FAC Ziziphus spina-christi (L.) Desf. LSEPh - IL AT CA RT AS AL ME NZ PA FAC FAC The nine reference mountain regions include: IL ¼ Iceland, Glacier Forelands of the Arctic Tundra; AT ¼ Alaskan Taiga, South Central Alaskan; CA ¼ Canadian Rocky Mountains; RT ¼ Russian Taiga, Northeast Siberian Mountains; AS ¼ Central Asia, Hindu-Kusch-Karakorum-Himalaya-Regions; AL ¼ Alps, Europe; ME ¼ Middle East, Wadis; NZ ¼ New Zealand, Southern Alps; and PA ¼ Patagonia, Southern Andes. Fig. 4 A braided river fed by glacial meltwater in the extensive glacier forelands in the south-western region of Vatnajökull. (Photo: G. Egger). Encyclopedia of Inland Waters, (2022) Author's personal copy STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers 191 Fig. 5 Vatnajökull dry gravel foreland, approximately 30 to 50 years old, dominated by Racometrium ericoides mossheath with Empetrum nigrum and Thymus praecox and several other vascular plants. (Photo: S. Metúsalemsson). Fig. 6 A moist sandy floodplain at Vatnajökull. The Juncus arcticus meadow includes Carex nigra, Calamagrostis neglecta, Salix lanata, S. phylicifolia and numerous other vascular species and provides a habitat rich in bird life. (Photo: S. Metúsalemsson). Encyclopedia of Inland Waters, (2022) Author's personal copy 192 STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers On more stable habitats—the ‘biogeomorphic phase’—young successional dwarf shrubs occur, such as the spreading Empetrum nigrum and Calluna vulgaris. In addition to the listed species of the pioneer phase, Thymus praecox ssp. arcticus, Alchemilla alpina, Botrychium lunaria, Campanula rotundifolia, Cerastium alpinum, Erigeron borealis, Luzula spicata, Minuartia rubella, Poa glauca, Saxifraga oppositifolia, Silene suecica also establish here (Magnússon et al., 2016). Further, low-growing willow species such as Salix lanata, S. phylicifolia and S. herbacea and Betula pubescens are also present (Aradottir and Eysteinsson, 2005; Vilmundardóttir et al., 2015). As succession progresses, habitats become increasingly species-rich and a number of further mosses, such as Racomitrium lanuginosum, Pogonatum urnigerum, Ceratodon purpureus, Lecanora polytropa, Placopsis gelida, Tremolecia atrata, Cetraria muricata, Cladonia borealis and Stereocaulon alpinum are present in addition to Racomitrium ericoides. On undisturbed moraine sites that have been ice-free for 60–120 years, mosses and lichens became more dominant in the ‘early successional ecologic phase’. On sites more heavily grazed by sheep, these transition to the widespread Vaccinium-EmpetrumRacomitrium heaths in the lowlands of Iceland (Magnússon et al., 2016). Also, on the oldest sites with moderate sheep grazing, dense and species-rich willow scrubland and birch woodlands occur with Betula nana, B. pubescens and Sorbus aucuparia and in the understory Salix lanata, S. arctica and dwarf shrubs such as Vaccinium uliginosum, Vaccinium myrtillus, Calluna vulgaris, Arctostaphylos uva-ursi and Empetrum nigrum are present as well as grasses, tall forbs, and Equisetum spp. (Aradottir and Eysteinsson, 2005; Glausen and Tanner, 2019; Magnússon et al., 2016). Despite the fact that nearly 336 alien plant species have been recorded in Iceland from 1840 to 2012, with about three new taxa added annually, only Lupinus nootkatensis and Anthriscus sylvestris can be currently classified as invasive non-natives along the rivers (Wasowicz et al., 2013). Originally from Alaska, L. nootkatensis occurs mainly in the ‘pioneer phase’ and is also common in the lowland areas of the moraines around Vatnajökull, where it is expected to spread extensively in the near future (Guðjohnsen and Magnússon, 2019). South Central Alaska Region, Alaskan Taiga This reference region covers the mountain ranges of southern Alaska and includes the Alaska Range (no. 9), Aleutian Range (no. 11), Chugach Mountains (no. 52), Elias Range (no. 78), Kenai Mountains (no. 113) and Wrangell Mountains (no. 221) (Fig. 2). These geologically relatively young, Cenozoic mountain ranges lie in the boreal climate region and have median elevations between 520 and 1200 m with the highest peak being Mount Logan (5959 m) in the Elias Range. Conversely, the Aleutian Range in the far west of Alaska has lower altitudes, lower precipitation and warmer temperatures. The Aleutian Range and Alaska Range in the southwest currently have small areas covered by ice (below 8%). In the other mountain ranges the area covered by glaciers ranges from 16% to 31%. In the last glacial maximum these were almost completely glaciated. Current vegetation cover across these mountain ranges varies between 54% and 84%. The tree line drops to 500 m near the Gulf of Alaska which is relatively low compared to other reference regions and peaks in the Wrangell Mountains with around 1300 m. The largest rivers of the south-central Alaskan region are the Copper, White, and Kenai Rivers and the headwaters of the Tanana River, such as the Delta, Nenana and Chisana River. The braided rivers of this study region are generally characterized by extensive areas of gravel (geomorphic phase) (Figs. 7 and 8). The subsequent ‘pioneer phase’ on these floodplains of the bare alluvium include colonization of herbs common in the Alaskan taiga such as Saxifraga aizoides, forbs like Lupinus polyphyllus, Solidago canadensis, and grasses like Phalaris arundinacea. Fig. 7 Susitna River in the south of Denali National Park (Alaska Range). (Photo: G. Egger). Encyclopedia of Inland Waters, (2022) Author's personal copy STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers 193 Fig. 8 Riverbed of the Delta River, a tributary of the Tanana River, with large amounts of dead wood (large woody debris). (Photo: G. Egger). This system progresses in the ‘biogeomorphical phase’ through stands dominated by Salix alaxensis, one of the most common and widespread pioneer willow species of the mountain regions of south central Alaska (Fig. 9). One of the most common pioneer trees of the ‘early successional ecologic phase’ is Populus balsamifera, which is abundant in the boreal regions across Canada. This fast-growing and generally short lived tree grows trans- continentally on upland and floodplain sites, where it has the best growing Fig. 9 An early successional woodland with dense willow shrubs dominated by Salix alaxensis and young Populus balsamifera trees along the East Fork Chulitna River, Alaska. (Photo: G. Egger). Encyclopedia of Inland Waters, (2022) Author's personal copy 194 STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers conditions. Along Pacific drainages, the closely related Populus trichocarpa (syn. Populus balsamifera ssp. trichocarpa), the largest of the American poplars, forms extensive groves at low elevations. Alnus incana is an abundant, large shrub on wetter sites on sand and gravel bars, in glacial and riparian shrublands and wet uplands from central to southern Alaska (Larson, 1994). Widely distributed along streams, rivers and in swamps and moist alluvial bottomlands from Alaska to the South of California and south-eastwards across North America, Salix lucida is a fast growing, deciduous large shrub or small tree. In addition, a number of other representatives of early successional willows are found such as S. arctica, the northernmost woody plant in the world (Woodward, 2014), and Salix glauca. Both are very common willows in shrubby riparian and tundra habitat. Other willows are less common such as Salix lanata, S. arctophila, S. pseudomyrsinites, S. interior, S. pseudomyrsinites, and S. brachycarpa ssp. niphoclada. Salix exigua, a widely-distributed species occurs on finer sediments of floodplains and lower elevations to lower montane habitats across western North America. Other willows and willow hybrids also occur including Salix arbusculoides, which is widespread along river banks from central Alaska to Hudson Bay, colonizing fresh alluvial deposits and glacial outwash. When initial trees of the “early successional phase of the forest” reach their maximum age and die, the dominant tree of the subsequent mid to ‘late successional ecologic phase’ is Picea glauca. This shade tolerant tree dominates the extensive boreal forests of Alaska and Canada. It occurs in all stages of boreal forest succession and also on recently disturbed sites. At poorly drained back swamps Picea glauca is replaced by Picea mariana. In the largely remote and relative pristine regions, there are relatively few invasive plant species along the braided rivers in the Alaskan taiga, including Sorbus aucuparia, Sonchus arvensis and Tanacetum vulgare. Canadian Rocky Mountains This region comprises the mainly boreal Coast Mountains (no. 54), Columbia Mountains (no. 56) and the Canadian Rocky Mountains (no. 161) (Fig. 2). Compared to the Alaskan region, the mountain ranges of this region are older (Mesozoic), current ice cover is lower and vegetation cover is higher (82–97%). The highest peak is Mount Waddington in the Coast Mountains and the largest rivers are the Yukon, Fraser, Columbia and Kootenay Rivers. The Canadian, or northern Rocky Mountains display braided, multi-thread river channels of three types. First, and similar to some other mountain regions on the Globe, as the mountain rivers drop down to shallower gradients, glacial scour and alluvial sediments are deposited, choking channels and leading to channel deflection and bifurcation. This generates very dynamic braided segments with sparse vegetation. The gravel bars of the ‘pioneer phase’ (Fig. 10) are commonly colonized by pioneers such as Dryas drummondii, which supports symbiotic actinorrhizal nitrogen fixation that is beneficial in an environment of nutrient-deficient mineral surfaces. Disturbance responsive plants like Epilobium angustifolium ssp. angustifolium create by aggradation slightly higher and more stable areas on which willows (listed below) and eventually Pinus contorta forests establish. As rivers flow downstream, Fig. 10 Pioneer phase with Dryas drummondii at the Sunwapta River in Alberta, Canada. (Photo: S. Rood). Encyclopedia of Inland Waters, (2022) Author's personal copy STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers 195 there are commonly progressive transitions from braided to meandering forms. These support arcuate bands or vegetation patches that result in a shifting mosaic of riparian community types. On the lower elevations the wet meadow zones that are commonly inundated, include the sedges Carex aperta, C. aquatilis, C. lenticularis and horsetails (E. arvense, Equisetum fluviatile). The willows include Salix bebbiana, S. boothii, S. brachycarpa, S. drummondiana, S. eriocephala, S. geyeriana, S. monticola, S. planifolia, and S. wolfii, with complexities in classification due to hybridization and introgression. Cornus sericea occurs on slightly higher surfaces of the ‘biogeomorphic phase’ contributing to the riparian shrublands. These blend into the slightly higher ‘early successional ecologic phase’ with riparian forests composed of Populus balsamifera along eastern drainages and P. trichocarpa (Fig. 11) along Pacific drainages. Alnus incana is common, and sometimes birches (Betula occidentalis, B. glandulosa) and Acer glabrum. Picea glauca and hybrids co-occur or follow with forest succession that may lead to the ‘late successional ecologic phase’, with Thuja plicata in wetter zones (Egger et al., 2015) (Fig. 12). Fig. 11 Colonization of black cottonwoods (Populus trichocarpa) following a flood of the Elk River in British Columbia, Canada. (Photo: S. Rood). Fig. 12 White spruce (Picea glauca) forest (late successional ecologic phase) with a few black cottonwoods (Populus trichocarpa; center of picture) representing a remnant from the previous early successional ecologic phase at the Elk River BritishWaters, Columbia,(2022) Canada. (Photo: G. Egger). Encyclopedia of inInland Author's personal copy 196 STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers The second type of regional river braiding, anastomosed channels, are very different relative to dynamics and vegetation distribution (Makaske et al., 2002). These occur in the broad and very shallow gradient glacial valleys, where post-glacial sediment deposition produces wide and flat floodplains with an interwoven complex of braided channels, wetlands and ponds. The complex braiding has been somewhat stabilized and natural levees flank the larger channels, following overbank sediment deposition. This inverts the elevational profile, with the higher surfaces adjacent to the river channel. Similar plants occur along the anastomosed channels but with opposing distribution. The black cottonwood (Populus trichocarpa) bands are directly along the channel on the elevated levees, and then sloping downward away from the channel to shrublands occur with willows (Salix spp.) and dogwood (Cornus sericea), and then lower surfaces with wet meadows and wetland ponds. A third type of river channel braiding occurs as rivers flow into natural lakes or artificial reservoirs. Sediment deposition creates the river delta with shallow topographies and distributaries form as the channels are choked and redirected. The same riparian vegetation communities form as along the other regional channel types, with the same spatial transitions with increasing elevation and correspondingly reduced inundation: from wet meadow, upwards to riparian shrubland, riparian forest and then the transition to upland, coniferous forest. In addition, with lower zones or with sediment lenses that limit drainage, there may be wetland zones with perennial ponding that support bulrushes and other emergent aquatic plants. Across these different braided and meandering channels and delta zones, a common invasive plant is Phalaris arundinacea (Spyreas et al., 2010). This plant is regionally native but vigorous hybrids have been developed and distributed as forage crops and these have invaded natural areas. A number of knapweeds (Centaurea diffusa; C. maculosa) and leafy spurge (Euphorbia esula) are also invasive in the riparian zones, especially in drier regions (Sheley et al., 1998). Northeast Siberian Mountains, Russian Taiga Northeast Siberia’s mountains east of Lena River, Verkhoyansk Range (no. 213 including Suntar-Khayata Range (no. 197)) and Cherskiy Range (no. 50 including Momskiy Mountains (no. 137) (Fig. 2) stretch for approximately 1000 km from north to south, and cover nearly the same distance in a longitudinal direction. Median elevations are 510–1380 m (max. 3003 m a.s.l.). The largest rivers are the Indigirka River (Fig. 13), Yana River, and Kolyma River. Despite the boreal climate with low mean annual temperatures of about 16 C and limited precipitation of below 300–420 mm, there are very few current glaciers. In contrast, at the last glacial maximum 20–84% of the mountain ranges were covered by ice. The vast area of Siberia, along with complex geomorphology, determines the diversity of vegetation patterns there. In the highlands, belts developed along the slopes according to the Verkhoyansk-Kolyma altitudinal zonation type (Ogureeva et al., 1999): mountain taiga, subalpine shrubs, mountain tundra, epilithic lichens belt, and the high mountains above snow line (“nival belt”). Along with that ecosystem diversity, narrow and deeply incised river valleys support specific vegetation complexes that include forests and shrubs intermixed with meadows, bogs and aquatic vegetation. The mountain taiga belt is limited to 600 m a.s.l. in the north and 1300 m in the south and is represented by the northern taiga of Larix gmelinii (Isaev et al., 2010). Valley complexes are most developed within this belt. Riparian forests of the ‘late successional Fig. 13 View into the valley of a tributary to the Indigirka river in its middle reaches in the Cherskiy Range with icing. (Photo: E. Troeva). Encyclopedia of Inland Waters, (2022) Author's personal copy STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers 197 ecologic phase’ with Larix gmelinii, Alnus alnobetula ssp. fruticosa and Rosa acicularis in the understory are more productive than the upslope communities. Along with larch, the late-successional forest stages in the Verkhoyansk Range features Picea obovata (Nikolin, 2014). At the lower floodplain levels, rapidly growing pioneer woodlands of the ‘early successional ecologic phase’ (Populus suaveolens, Chosenia arbutifolia, Betula pendula, B. pubescens) establish (Nikolin, 2012, 2013). Chosenia arbutifolia is a characteristic riparian species adapted to mountain rivers’ high hydro- and morphodynamics. It germinates and establishes upon open gravel and sand banks along the active channel. After 12–25 years it can also dominate the ‘biogeomorphic phase’, growing up into deciduous forests approximately 25–30 m high. These floodplain forests can subsequently get ages of 60–120 years (Moskalyuk, 2016; Fig. 14). In the border areas along the active channels, arborescent willow stands (Salix schwerinii, Sapromyza rorida, Salix viminalis, etc.) form intermixed with forb and grass meadows. Within the subalpine shrub belt (Pinus pumila, Betula divaricata, ca. 1000 m a.s.l.), low shrubs (Betula nana subsp. exilis, Salix pulchra, S. saxatilis) separate slope communities, and riparian willows (Salix alaxensis, S. boganidensis, S. dshugdshurica, S. pseudopentandra) grow along the active channels. Occasionally, P. pumila extends downslope down to the river. Shrubs alternate with bogs (Carex spp., Eriophorum spp.) and small patches of meadow (Carex spp., Kobresia spp.) (Nikolin, 2014). Open gravel alluvium is a substrate for the ‘pioneer phase’ with communities of Equisetum arvense. Further silt accumulation provides habitat conditions for Chamerion latifolium (Fig. 15) and graminoid meadows (Bromus spp., Leymus spp., Calamagrostis spp.). When considering the Northeast Mountains’ river corridors, it is necessary to recognize the unique phenomenon of aufeis, or icing (Fig. 13). Sheet-like masses of aufeis form from successive flows of groundwater during freezing temperatures. Melting icings are surrounded by communities of Equisetum variegatum, which is a valuable forage plant for horses and for native ungulates and other herbivores. Towards the edges of gravel-bed rivers, these are replaced by meadows of Calamagrostis neglecta, Carex spp., Pedicularis spp., Primula spp., Ranunculus spp. and other plants (Efimova et al., 2010). The river valleys are less systematically developed within the mountain tundra belt (1110–1500 m a.s.l.). Complex tundra communities (Ledum palustre, Arctous alpina, Koenigia tripterocarpa, Andromeda polifolia, Empetrum nigrum) with sparse shrubs of B. nana subsp. exilis represent a transition between upslope and riparian vegetation. On sandy-gravel alluvia, mesic meadows (Leymus interior, Bromus pumpellianus s.l.) develop. Ribbon-like thickets of low-growing willows (Salix alaxensis, S. lanata, S. glauca, S. pulchra, etc.) with sporadic Calamagrostis purpurea communities are confined to stream banks (Efimova et al., 2010; Nikolin, 2014). There are no serious invasive non-native plants in these riparian zones. Fig. 14 The biogeomorphic succession phase with Salix spp. and Chosenia arbutifolia along the East Khandyga River bank (Verkhoyansk Range). (Photo: E. Troeva). Encyclopedia of Inland Waters, (2022) Author's personal copy 198 STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers Fig. 15 Chamerion latifolium is a characteristic species of the pioneer phase of river corridors in the mountains of northeast Siberia. (Photo: E. Troeva). Hindu Kusch-Karakorum-Himalaya-Region, Central Asia The very high mountains of this region are heterogeneous in terms of global climatic types. These range from the monsoon-shaped subtropical south-eastern part of the Himalayas (no. 104) with extremely high tree lines up to 4000 m m.a.s.l. to the Eurasian winter humid subtropics in the Hindu Kush (no. 105) and the western Karakoram (no. 111), and to the north-western slope of the Hindu Kush Pamirs (no. 148) characterized by the winter humid continental dry climate. These also include the temperate climate of the Kunlun Shan (no. 122), the cold continental climate of Tian Shan (no. 203) on the Tarim Basin’s edge, and the Borohoro Mountains (no. 35) (Fig. 2). The global climatic zones are strongly dominated by altitude and determine vegetation structure to a large extent (Schultz, 2005). Thus, the mountain ranges of Central Asia differ substantially from the other selected mountain regions of the arctic and temperate boreal zones of the northern and southern hemispheres, or the wadis of the Middle East. With exception of the Borohoro Mountains, these mountain ranges have maximum elevations of more than 7.150 m m.a.s.l. and comprise the highest peaks of the world. As a consequence, runoff from snow and glacier melt is very important for the rivers especially in the arid part of this region, even though the current ice cover ranges only from 2.7% to 14.5%. Several large rivers have their sources in these mountains, notably the Ganges, Indus, Brahmaputra, Yarkand and Ili Rivers. In addition to the regional climatic complexity, vegetation spreads over several floristic provinces providing additional complexity for a comprehensive overview (Grubov, 2010). Information on these region’s floodplain ecosystems is scarce and consequently we focus on the rivers of the Tian Shan, where scientific studies have been undertaken (Betz, 2021; Kamelin, 1973). One distinctive riparian vegetation type in Central Asia is the Tugai floodplain forest. It extends far beyond the mountainous regions and is centered in the continental, cold winter deserts. These floodplain forests stretch from the middle reaches of rivers in the mountains to the lower reaches of the major inland rivers in Uzbekistan, Kazakhstan, Tajikistan (Fig. 16) and Turkmenistan. Major rivers include the Amu Darya and Syr Darya in the Aral Sea Basin. Tugai forests also occur along the Chu and Ili Rivers in Kyrgyzstan and Kazakhstan. Tugai forests have also been described in the eastern Tian Shan region along the Tarim River as well as in the Gobi Desert of Western Mongolia (Schulz and Kleinschmit, 2019; Tesch and Thevs, 2020; Treshkin et al., 1998). The key species of Tugai forests along the middle and lower reaches of the rivers are Populus pruinosa and P. euphratica (Aishan et al., 2015; Thevs et al., 2008, 2012). In the ‘early successional ecologic phase’, these poplars occur in association with Elaeagnus angustifolia, Tamarix ramosissima, T. hispida, T. elongate, Halostachys caspica, Halimodendron halodendron, Alhagi sparsifolia and Myricaria pulcherrima (Aishan et al., 2015; Thevs et al., 2008; Treshkin et al., 1998). In some cases, Salix songarica and S. wilhelmsiana also occur (Rüger et al., 2005; Treshkin et al., 1998). However, these species and Populus pruinosa were severely disturbed due to anthropogenic impacts to the river regime (Halik et al., 2019; Rüger et al., 2005). In the frequently inundated zone closer to the river, the ‘biogeomorphic phase’ is composed of a mosaic of Populus euphratica shrubs, Phragmites australis and Calamagrostis pseudophragmites (Thevs et al., 2008). Tugai forests dominated by Populus euphratica stretch along the lower reaches of the Central Asian rivers and differ significantly from the riparian forests along the upstream river reaches in the mountains. Betz (2021) has described the riparian plants along the Naryn River in Kyrgyzstan, a braided gravel-bed river along most of its course. For the ‘pioneer phase’, juvenile individuals of Salix babylonica, Populus nigra, Tamarix chinensis and Hippophae rhamnoides are typical (Betz, 2021). Encyclopedia of Inland Waters, (2022) Author's personal copy STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers 199 Fig. 16 A braided river section of the Obikhingo River valley in Tajikistan. (Photo: N. Lashchinskiy). The most frequent species of the ‘biogeomorphic phase’ are Hippophae rhamnoides (Fig. 17), Salix babylonica and Populus nigra. The last species becomes dominant in the ‘early successional ecologic phase’ (Fig. 18). In its understory, thickets of Rosa spp., Berberis vulgaris, Elaeagnus angustifolia and Caragana spinosa are accompanied by Carex spp., Artemisia vulgaris and Phragmites australis. This species composition is consistent with the findings of Imanbardieva (2015), for floodplain vegetation along the At Bashe River, a tributary of the Naryn River. River terraces form the boundary of the floodplain forests along the Naryn River, whereas Fig. 17 Sallow thorn (Hippophae rhamnoides) is a typical species in the pioneer and biogeomorphic phases along the Naryn River, Kyrgyzstan. (Photo: F. Betz). Encyclopedia of Inland Waters, (2022) Author's personal copy 200 STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers Fig. 18 Poplar forest (Populus nigra) on the floodplain of the Naryn River, Kyrgyzstan. (Photo: F. Betz). hardwood forests of the late-successional stage are unusual (Betz et al., 2020; Betz, 2021). The absence of late-successional forests is also characteristic for the Central Asian floodplains, where climatic conditions lead to a transition of the early successional woodlands directly into forest-steppe, steppe or desert forests (Pfadenhauer and Klötzli, 2014). In the middle reaches of the Western Tian Shan and Pamir-Alay rivers, and especially in valleys open to the west, there are riparian forests composed of Fraxinus species in the tree layer or forest canopy and well-developed, species rich herbaceous layers providing the understory (Kamelin, 1973, 1990; Lashchinsky et al., 2019). The mild climate of these valleys preserves Fraxinus forests as late-successional stage vegetation (Fig. 19) and these forests could be considered as relicts of Paleogene subtropical floodplain forests (Kamelin, 1973). Fig. 19 Fraxinus riparian forest in the western Tian Shan mountains. (Photo: N. Lashchinskiy). Encyclopedia of Inland Waters, (2022) Author's personal copy STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers 201 In the upper reaches of Pamir, Tian Shan and Pamir-Alay regional rivers, riparian birch forests with Betula tianschanica and B. procurva are common on the floodplains (Kamelin, 1973; Safarov, 2003). Salix fragilis is another common woody species in the riparian forests of Central Asia (Pfadenhauer and Klötzli, 2014). There are relatively few alien plant species in the riparian forests of Central Asia, with Ailanthus altissima as the most common invasive plant for the ‘early successional ecologic phase’ of riparian forests in the middle reaches of the Tian Shan rivers. Alps, Europe The Alps in Europe (no. 12) (Fig. 2) have a mean elevation of 840 m and their maximum peak of 4.810 m with Mont Blanc in France. The moderate to Mediterranean climate with a mean annual temperature of 7.4 C, mean precipitation of 1.023 mm and only about 1.2% glaciation of the mountain range allows for the development of extensive vegetation cover over about two thirds of the Alps. The early human influences on the alpine rivers through 19th century included bank stabilization and later increased hydraulic-engineering and river regulations enabled human land use and resulted in current population densities of almost 100 inhabitants/km2. About one third of the alpine river catchments is covered by settlements or croplands and the largest rivers of the Alps include the Rhine, Sava, Inn, Drava, Rhône and Tagliamento Rivers (Fig. 20). The most active channels of braided rivers in the European Alps are dominated by gravel bars without vegetation. Less frequently disturbed bars are sparsely vegetated with herbaceous plants and shrubs, often with only a few species. Characteristic plant species restricted to braided river corridors in the ‘pioneer phase’ include Calamagrostis pseudophragmites, Chondrilla chondrilloides, Epilobium fleischeri, E. dodonei, Scrophularia canina and Typha minima. These are accompanied by common species from the surrounding vegetation (Egger et al., 2019a; Kalníková et al., 2021). For the ‘biogeomorphic phase’, Salix eleagnos is often the most frequent species of river corridors in the Alps. Further characteristic species are Salix purpurea, S. daphnoides, Myricaria germanica (Fig. 21) and Hippophae rhamnoides subsp. fluviatilis. Less disturbed but regularly inundated floodplain areas characterize the ‘early successional ecologic phase’ with riparian forests dominated by Alnis incana. These extend up to an altitude of about 1.400 m in the Eastern Alps and 1.900 m in the Western Alps. The lower limit is about 250 m a.s.l. in the Southern Alps (Italian Eastern Alps) and about 900 m a.s.l. in the French Western Alps. In lower altitudes of the Western Alps A. incana (Fig. 22) is replaced by Populus nigra and in the Mediterranean locations, and complemented by Populus alba. In the lower Alps and the alpine foreland, Salix alba often dominates the floodplain forests. Common deciduous trees of the ‘late successional ecologic phase’ are Quercus robur, Carpinus betulus, Ulmus laevis, and U. minor. Today these forests have become rare due to the extensive human impacts on the river ecosystems since the 19th century. On dry Fig. 20 The Tagliamento river in the Southern European Alps (Italy) is the longest and largest remaining unregulated braided river of the Alps. (Photo: B. Kaltenböck). Encyclopedia of Inland Waters, (2022) Author's personal copy 202 STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers Fig. 21 Myricaria germanica is well adapted to the high morphodynamics that characterize braided rivers like at the Upper Isar in the Alps. (Photo: I. Becker). Fig. 22 The grey alder (Alnus incana) floodplain forest is the most widespread woodland community along the rivers of the Alps. (Photo: G. Egger). Encyclopedia of Inland Waters, (2022) Author's personal copy STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers 203 gravel bars that are no longer inundated, Pinus sylvestris forests can be found throughout the Alps. The riparian corridors of the montane to subalpine zones are often associated with Alnus alnobetula and in the late successional phase with Picea abies. In the European Alps, a large number of invasive non-native species especially from North America and East Asia have spread along the corridors of the braided rivers. The introduced plants are especially frequent in floodplains where river dynamics have been altered by humans and/or in floodplains at lower and warmer elevations. Most invasive species can be found in the ‘pioneer phase,’ including Ambrosia artemisiifolia, Bidens frondosa, Impatiens glandulifera, Oenothera biennis agg. and Xanthium strumarium. In the shrub communities of the ‘biogeomorphic phase’, Amorpha fruticosa, Buddleja davidii, Fallopia japonica and Solidago canadensis are frequent. In the understory of floodplain forests of the ‘early successional ecologic phase’, Solidago gigantea often competes with the native species. In floodplain forests of the ‘late successional ecologic phase’ Ailanthus altissima and Robinia pseudoacacia are frequent throughout the Alps (Egger et al., 2019b; Müller and Okuda, 1998). Wadis in the Mountain Ranges of the Middle East A different kind of gravel-bed rivers occurs in the tropical climate present in this region. The rivers are located in the mountain ranges at the western and southern coastal regions of the Arabian Peninsula, named as the Al Hajar (no. 7), Asir (no. 22), Hadramaut (no. 95) and Hejaz Mountains (no. 102). The Ogo Mountains (no. 145) in Somalia at the Horn of Africa are also included in this type (Fig. 2). Deil and Al Gifri (1998) distinguish three major montane vegetation types for the Arabian Peninsula, the: (1) north-western Mediterranean vegetation type (majority of annual rainfall of 50–150 mm in winter and early spring), (2) south-western Afromontane type (majority of 200–500 mm of rainfall in spring and to a lesser extent in summer) and (3) eastern Omano-Makranian type (150–300 mm of rainfall mostly in the winter and early spring, with an additional summer rainfall peak in some years). The regional mountains were not glaciated in the last glacial maximum and remain non-glaciated today. Wadis (or the Arabic, ‘Oued’) are river beds in the Saharo-Arabian desert. Water flow can be seasonal as in sub-humid mountains with a rainy season, or after short, heavy rainfall, which is episodic or erratic with the arid climate. These river systems are accompanied by common, near-surface groundwater flow. Big wadis with large catchments can have permanent water channels along parts of their length, but no permanent river drains into the Red Sea or the Gulf of Oman. In broader river valleys with low gradients and nearly flat plain deserts, sudden but infrequent heavy rainfall causes flash floods (the Arabic, ‘Sayl’) and the erosion, re-deposition and accumulation of sediments. This leads to the formation of braided channel patterns of mixed gravels and sands. Braided wadis concentrate in the transition zone from the mountains of the Musandam Peninsula to the foreland, and from the Southwest Arabian Escarpment to the Central Arabian Desert, the Rea Sea coastal plain (‘Tihama’). For the latter area, a typical sequence of hydrological conditions including the riverbed gradient, frequency and intensity of water flow, groundwater level and characteristic riverine plant species is presented with the example of Wadi Mawr (Yemen; Fig. 23). It is an allochthonous wadi, with Fig. 23 Wadi Mawr in the Basin of At Tur, Mountainous Tihama, Jemen. Gallery thickets with evergreen shrubs (Tamarix nilotica, T. aphylla, Salvadora persica) colonize the sandy terraces. Terraces in the foreground were cleared for millet cultivation. (Photo: U. Deil). Encyclopedia of Inland Waters, (2022) Author's personal copy 204 STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers Fig. 24 The Wadi Labtah, Syria, with remnants of gallery forest with broadleaved species (Combretum molle, Berchemia discolor, Combretaceae) and raingreen umbrella-shaped trees (Acacia johnwoodii, Tamarindus indica, Fabaceae). (Photo: U. Deil). water flow in the semi-arid Basin of At Tur and the arid coastal plain triggered by rainfall events in the sub-humid upper parts of the catchment area. The sequence starts in the higher Escarpment with riverine trees of the ‘late successional ecologic phase’ such as Breonadia salicina, Ficus spp. (F. vasta, F. populifolia, F. sycomorus, F. cordata ssp. salicifolia) and the palm, Phoenix reclinata. These are replaced in the lower Escarpment and Mountainous Tihama by the broad-leaved, freshwater phreatophytes of the ‘early successional ecologic phase’ such as Combretum molle, Berchemia discolor and Trichilia emetica (Fig. 24). Sandy riverside terraces are colonized and stabilized by the Acacia ehrenbergiana-Jatropha curcas-Desmostachya bipinnata community of the ‘biogeomorphic phase’. The riverbeds in the arid coastal plain (Tihama) contribute to this phase and are colonized by salt-tolerant evergreen Tamarix shrubs (Tamarix nilotica, T. aphylla), Salvadora persica, the flash flood resistant tall bunchgrass, Saccharum spontaneum, and by the soft-wooded shrub, Calotropis procera (Fig. 25). Intermittently flooded low terraces along broad wadis and active channels with fine grained sediments are covered with a layer of creeping and rooting herbs of the ‘pioneer phase’, including Bacopa monnieri, Eclipta alba, Fimbristylis spp. and Phyla nodiflora (Deil and Müller-Hohenstein, 1985; Patzelt, 2015). A liana veil with Cissus quadrangularis, Leptadenia arborea and Cocculus pendulus may border the riverine thickets. Relief, substrate texture (grain size), hydrology and morphodynamics (stream velocity) are the main differentiating factors across the wadis. The vegetation patterns, characteristic plant species and life forms of a small wadi with remnants of gallery forests are documented by transects and riverside catenae by Deil (1986), Deil and Al Gifri (1998) and Deil and Müller-Hohenstein (1985). Common wadi species throughout the Arabian Peninsula are Tamarix shrubs (T. nilotica s. str., T. senegalensis, T. mascatensis, T. aucheriana, T. aphylla) and tall bunch grasses of the genus Saccharum (S. spontaneum, S. kajkaiense, S. griffithii, S. ravennae). Additionally, Jatropha species (J. glauca, J. pelargoniifolia) characterize alluvial plains in the frost-free tropical lowlands, Rhazya stricta is common in the wadis with extratropical climates of the Arabian Peninsula (Deil and Al Gifri, 1998). In less arid conditions, Rhazya stricta is replaced by Nerium species (N. oleander, N. mascatense). A Saccharum griffithii-Nerium mascatense-Dyerophytum indicum-community was described from United Arab Emirates (Deil and Müller-Hohenstein, 1996) and further wadi species on the Peninsula are Retama raetam in the northwest, Pistacia atlantica in the north, and the widely distributed phreatophytes, Prosopis cineraria and Ziziphus spina-christi. Intermittent water flow through the braided river corridors from the sub-humid mountains to the arid coastal plains is used for agriculture by diverting flash floods into walled fields (Sayl irrigation). Alluvial groundwater is overexploited by pumping for irrigation and by plantations of the deep-rooting date palm (Phoenix dactylifera). A noxious weed and aggressive invader of sandy terraces and irrigation runnels is Imperata cylindrica. This plant has wide native ranges from Africa to Asia but is non-native to the wadis of the Middle East. Encyclopedia of Inland Waters, (2022) Author's personal copy STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers 205 Fig. 25 Saccharum spontaneum and Calotropis procera stabilizing fine sediments in Wadi al Kharid, in the Eastern Yemeni highlands. (Photo: U. Deil). Southern Alps, New Zealand The Southern Alps on the South Island of New Zealand (no. 191) (Fig. 2) are characterized by temperate rain forests in the west, partially glaciated summit regions (current ice cover 2.6% of mountain range) with extremely high precipitation of 3.000–4.000 mm/year or more in the central region, and progressively drier lowlands to the east. Here, a number of large, braided rivers such as the Rakaia, Rangitata and Waimakariri (Fig. 26), with riverbeds up to about 500 m wide, flow eastward from the Southern Alps. Species of the genus Raoulia are the most frequent and characteristic plants in the ‘pioneer phase’ of the extensive braided river corridors. On dry gravel alluvia in the mountain valleys with moderate to high rainfall, the lichen species Raoulia tenuicaulis, R. haastii, R. monroi, R. parkii and R. australis are widespread. These are associated with Epilobium species such as E. brunnescens, E. nummularifolium subsp. nerterioides, E. microphyllum, E. melanocaulon and E. glabellum (Meurk and Williams, 1989; Wardle, 1991; Woolmore, 2011; Fig. 27). Additionally, there are common widespread grasses such as Lachnagrostis lyallii and L. filiformis, and along the subalpine and lower alpine gravel-bed rivers also Rytidosperma setifolium and Poa novae-zelandiae (Wardle, 1991). The most widespread shrub of the sparsely vegetated ‘biogeomorphic phase’ is Coprosma brunnea. Further woody plants on stabilized alluvium include Muehlenbeckia axillaris, Coprosma brunnea and additionally Helichrysum depressum, Carmichaelia nigricans, C. grandiflora, Discaria toumatou and Leptospermum scoparium, along with the mosses, Polytrichum juniperinum and Racomitrium spp. (Wardle, 1991; Meurk and Williams, 1989; Müller et al., 2017). In the western region of the South Island, there are still natural floodplain forests of the ‘ecologic phase’, as described by Miller (2004). The most common species in the canopy and sub-canopy of these ‘late successional’ communities are the conifers Dacrycarpus dacrydioides, Dacrydium cupressinum, Prumnopitys ferruginea, the evergreen tree Leiospermum racemosum, and Nothofagus menziesii, the most widely distributed beech taxon in New Zealand. In the upper shrub tier, the tree fern Dicksonia squarrosa is very common. In contrast to the western slopes, the lowlands in the east had already been extensively cleared by the turn of the 20th century, and the natural riparian forests are highly fragmented. Under natural conditions, the flora of New Zealand is characterized by about 80% endemic species (McGlone et al., 2001). Today, many river corridors are dominated by alien species, with abundances of up to 60% (Williams and Wiser, 2004). While the headwaters still tend to be dominated by native species, the lower river reaches are often dominated by alien, non-native plants (Woolmore, 2011). Additionally, alien species cover is higher in rivers with higher maximum flows, especially in areas with fine substrate textures and on higher terraces along the rivers (Brummer et al., 2016). Frequently, invasive non-native species from the Encyclopedia of Inland Waters, (2022) Author's personal copy 206 STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers Fig. 26 The upper reach of the Waimakariri River near Arthur pass is typical of the braided rivers in the Southern Alps of New Zealand. (Photo: N. Müller). Fig. 27 In the headwater and upper reaches of rivers from the Southern Alps of New Zealand, native and endemic species (here, Epilobium melanocaulon) are typical for the pioneer phase. (Photo: N. Müller). Encyclopedia of Inland Waters, (2022) Author's personal copy STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers 207 Fig. 28 Along the lower reaches of some New Zealand rivers, invasive non-native species (here Cytisus scoparius and Lupinus polyphyllus flowering) are dominating from the pioneer to the early successional ecologic phase. (Photo: N. Müller). ‘pioneer phase’ to the ‘early successional ecologic phase’ include the European grasses, Agrostis capillaris, A. stolonifera, Anthoxanthum odoratum, Holcus lanatus, Festuca rubra and Dactylis glomerata, the European herbs, Crepis capillaris, Hypochaeris radicata, Lotus corniculatus, Plantago lanceolata, Trifolium repens, T. arvense, Rumex acetosella, and Sedum acre, and the North American forbs, Lupinus arboreus and L. polyphyllus (Fig. 28). Widespread invasive shrubs include Cytisus scoparius, Rosa rubiginosa, Salix x fragilis, and Ulex europaeus—all originating from Europe (Müller et al., 2017; Williams and Wiser, 2004; Woolmore, 2011). Southern Andes, Patagonia The Andes in South America are considered as the Patagonian Andes (no. 228) (Fig. 2) south of Rio Bio Bio in Chile and Rio Colorado in Argentina. By moving from North to the South, climate changes from moderate to boreal arctic. Further, the Andes act as barrier for precipitation originating from the Pacific Ocean and consequently the Argentinean regions are much drier than those in Chile (Fig. 29). The tree line in the south is very low at about 400 to 600 m a.s.l., and rises in the north to about 1.000 to 1.700 m. Currently, glaciers cover almost 11% of the mountain range and in the last glacial maximum almost 75% was glaciated. The largest rivers are the Colorado, Negro, Chubut and Santa Cruz Rivers. In Patagonia, the riparian zones are characterized by relatively low plant species richness as well as many other Patagonian ecosystems (Kellman, 1970). This is likely a result of the glaciation history (Mendelova et al., 2017), isolated location and restricted landmass of the Southern hemisphere, which limited colonization from other regions. The few specialized species of the floodplains (Lewerentz et al., 2019) are also distributed in areas with frequent and intense disturbance regimes like landslides and volcanic lahars. These areas of huge sediment loads are common in the vicinity of areas with volcanic activity (Iroumé et al., 2020) or glacial lake outburst floods (Ulloa et al., 2020). The open gravel and sand bars provide the ‘pioneer phase’ of the gravel-bed rivers of Patagonia and are characterized by native pioneer plants such as Agrostis inconspicua, Juncus scheuchzerioides, Gunnera magellanica and Acaena magellanica, as well as non-native species such as Plantago lanceolata, Prunella vulgaris, Trifolium repens, Holcus lanatus, Hypochaeris radicata and Agrostis stolonifera (Fig. 30). In addition, there are native shrubs such as Gaultheria mucronata, Berberis microphylla and Discaria chacaye, while Baccharis obovata may be the most abundant. These species establish sporadic stands in the highly disturbed ‘pioneer phase’ along the active channel and form patchy to closed shrub layers in the later ‘bio-geomorphological phase’. The taller native shrubs, Escalonia virgata, Fuchsia magellanica and Berberis empetrifolia and the non-native evergreen bamboo Chusquea culeou, are typical for the ‘early Encyclopedia of Inland Waters, (2022) Author's personal copy 208 STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers Fig. 29 The catchment area of the Rio Blanco is mainly located in the Parque Pumalín nature reserve near Chaitén, Chile and is characterized by an extensive and largely natural forest landscape. (Photo: G. Egger). Fig. 30 Pioneer phase with buzzy burr (Acaena magellanica) at Rio de los Ñadis, Chile. (Photo: G. Egger). successional ecologic phase’ of the regional riparian forests (Harmel, 2020). The only willow species of the natural flora is Salix humboldtiana, which occurs sporadically in the floodplains of northern part of Patagonia (southern limit 380 S). In general, in the ‘ecologic phase’ for these riparian communities the shrubs display higher species diversity while there are fewer tree species. The trees are commonly represented by the deciduous Nothofagus antarctica in the south and evergreen Nothofagus dombeyi in the north and/or rainier climate zones. While N. antarctica stands are rare, these do occur both as early successional stands on open gravel bars and as mature forests in the inactive floodplain zones. Evergreen tree species usually predominate in the ‘late successional ecologic phase’ of the riparian forests. They are often associated with further characteristic trees of Valdivian temperate rain forests, including Luma apiculata and Podocarpus nubigenus, and of deciduous forests of the temperate zone in Chile, such as Encyclopedia of Inland Waters, (2022) Author's personal copy STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers 209 Fig. 31 Species-rich floodplain forest (late successional ecologic phase) along the River Palena, Chile. (Photo: G. Egger). Nothofagus pumilio, N. betuloides, Pilgerodendron uviferum (Gut, 2008; Vidal et al., 2011) and occasionally, Amomyrtus luma and Embothrium coccineum (Harmel, 2020) (Fig. 31). In contrast to the pioneer woody plants from the genera Salix and Populus, these species hardly germinate on the open gravel and sandy areas of the active channel, but establish on morphologically more stable substrates of the biogeomorphic and ecologic succession stages (Lewerentz et al., 2019). Perhaps the most noteworthy aspect of Patagonian floodplains and riparian zones is the high abundance and sometimes complete dominance by alien plant species. Besides a potential vacant ecologic niche due to the lack of fast-growing early successional woody species and woodland phase, the invasion is facilitated by river regulation, road construction, a legacy of landscape scale wildfires, and clearing by logging and ranching activities. In this context, it is important to recognize the massive spread of the North American Lupinus polyphyllus in the ‘pioneer phase’ (Meier et al., 2013) and the European S. fragilis in the ‘biogeomorphic’ and ‘early successional ecologic phase’ (Harmel, 2020; Lewerentz et al., 2019; Fig. 32). In addition, a variety of alien woody species are common, including Elaeagnus angustifolia, Rosa rubiginosa, and Cytisus scoparius (Weber, 2017). Fig. 32 Salix fragilis invades gravel bars at the Rio de los Ñadis, Chile. (Photo: G. Egger). Encyclopedia of Inland Waters, (2022) Author's personal copy 210 STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers Conclusion and synthesis The species composition of the riparian vegetation of gravel-bed rivers is differentiated according to the global floral regions. Thus, the global research indicates that only a few naturally occurring species or even only a few genera are more common at several reference mountain regions (see Table 1). The majority of the investigated mountain regions with a high proportion of braided rivers are located in the boreal zone of the Northern Hemisphere such as the investigated mountain ranges of Alaskan Taiga, the Canadian Rocky Mountains, and the northeast Siberian Mountain ranges of the Russian Taiga (Maier et al., 2022). These boreal to sub-Arctic regions share common characteristics in climate and vegetation. Thus, the biogeomorphic phase is similarly occupied by a number of widespread, floodplain-typical ecologic pioneer tree and shrub species of the related genera Salix and Populus (Karrenberg et al., 2002). Further, native representatives of the genera Myricaria (Alps, Central Asia) and Tamarix (Central Asia) are also typical for the northern hemisphere. These species are characterized by prolific production of small, light seeds that are dispersed over wide areas by wind and water, the processes of anemochory and hydrochory, respectively. The obligate or facultative riparian plants also often display effective vegetative or clonal reproduction through root suckers or stump shoots. With typically vigorous growth, these ecological specialists are well adapted to the strong hydro-morphodynamics of the gravel-bed rivers. Poplars (Populus spp.), willows (Salix spp.) and tamarisks (Myricaria spp., Tamarix spp.) are naturally absent along the braided river corridors of the Southern Hemisphere, where there are fewer woody pioneer species restricted to the riparian ecosystems or floodplain zones (Meier et al., 2013). This results in open niches that are available for colonization by the introduced Northern Hemisphere pioneer shrubs and trees, especially along the lower reaches of gravel-bed river corridors where agricultural and urban areas are increasing. This has resulted in severe invasions and serious alterations to the native biodiversity, as documented for the braided river corridors of the Southern Andes in Patagonia and for the Southern Alps in New Zealand (Budde et al., 2011; Caruso et al., 2013; Lewerentz et al., 2019; Harmel, 2020). In contrast to the braided river corridors of the temperate zones, the Alps, Southern Andes and Rocky Mountains, the dominant tree species in established forests of the late successional ecologic phase differ in the Arctic zones, the Alaskan and Russian Taiga. In the Arctic taiga, conifers (Picea in North America or Larix in Eastern Russia/Siberia) that are adapted to the long, very cold winter months and very short vegetation period dominate the late successional ecologic phase. In contrast, in the temperate zones, flood-tolerant deciduous trees prevail, often from the genera Quercus, Ulmus or Fraxinus (Pfadenhauer and Klötzli, 2014). An unusual case of the Arctic boreal zone is displayed with the very young riparian ecosystems of the glacier forelands of the Arctic tundra below the extensively glaciated mountains of Vatnjajökull (Iceland). Iceland was almost completely covered by ice during the last ice age (Hallsdóttir, 1995) and today there are very few endemic plant species. This is explained by a continuous long-distance influx of seeds and clonal vegetative fragments by ocean currents, winds or birds following the Holocene and even earlier (Rundgren and Ingólfsson, 1999). At present, most of the glacier forelands of the Arctic tundra are covered by young successional stages. Also, there are no native conifer trees in Iceland, which contrasts with comparable climatic areas within the boreal zones in Alaska, Canada and Russia. These trees of the late successional phase did not survive the ice ages in Iceland, and due to the isolated island location have not immigrated until recently (Hallsdóttir, 1995). The continental floodplains of the inland rivers in Central Asia contrast to the riparian forests of the boreal and Arctic zones. In Central Asia, the early successional riparian forests of the ecologic phase tend to develop within a narrow corridor along the river channels and are often threatened by anthropogenic activities. Closed canopy, late successional riparian forests are mostly absent due to the arid climate. The wadis of the Middle East represent very distinctive gravel-bed river corridors. Accompanying the hot and dry climates, the active channels are often intermittent and are predominantly characterized by sparse phreatophytic floodplain vegetation such as Nerium spp. and Rhazya stricta along with a number of species of the genus Tamarix. It is notable that almost no endemic species occur in the river corridors of the reference regions in the Northern Hemisphere. The reason for this may be that the reference regions with a high proportion of braided rivers are mainly found in young (tectonic uplift) mountains and in most cases were covered by glaciers during the last glacial maximum. As a consequence, the time was too short and the environmental conditions too variable for the development of endemic species over the recent geological eras. In contrast, the braided river corridors of the Southern Alps in New Zealand show a different pattern, with a flora dominated by endemic species in all succession phases. Most of those characteristic endemic species are woody plants, as reported by McGlone et al. (2001). These patterns originate in the long history of geographical and evolutionary isolation (McGlone et al., 2001). Due to the biogeographic isolation by the surrounding oceans and the dry steppe to desert ecoregions in the east and north, the region of the Patagonian Andes is also characterized by a high proportion of endemic species (Rozzi et al., 2012). The endemic, riparian Nothofagus species also form the world’s southernmost forests (Rozzi et al., 2012). In addition to these riparian patterns, as revealed in Table 1, the majority of the selected characteristic plant species are not limited to floodplains, but are also present in adjacent, upland ecosystems. The plants are well-adapted to the local temperature regimes and display plant adaptations to the dynamic site conditions along the braided channels of the gravel-bed rivers. These life history requirements and ecophysiological adaptations also allow establishment in other regional sites with similar physical characteristics, such as with the rocky and stony habitats in the mountain regions, or in other disturbance-prone locations such as avalanche paths (Williams and Wiser, 2004). See Also: Structures and functions of Inland Waters - Groundwater: The Ecology of Aquatic Cave Environments; Structures and functions of Inland Waters - Rivers: Riparian Zones; Stream Geomorphology Encyclopedia of Inland Waters, (2022) Author's personal copy STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers 211 References Aishan T, Halik U, Betz F, Tashpolat T, Ding J, and Nuermaimaiti Y (2015) Stand structure and height diameter relationship of a degraded Populus euphratica forest in the lower reaches of the Tarim River, Northwest China. Journal of Arid Land 7(4): 544–554. Aradottir AL and Eysteinsson T (2005) Restoration of birch woodlands in Iceland. In: Stanturf JA and Madsen P (eds.) Restoration of Boreal and Temperate Forests. vol. 13, pp. 195–209. Boca Raton: CRC Press. Balke T, Herman PMJ, and Bouma TJ (2014) Critical transitions in disturbance-driven ecosystems: Identifying windows of opportunity for recovery. Journal of Ecology 102(3): 700–708. Bazzaz FA (1979) The physiological ecology of plant succession. Annual Review of Ecology and Systematics 10(1): 351–371. Bennett SJ, Wu W, Alonso CV, and Wang SSY (2008) Modeling fluvial response to in-stream woody vegetation: Implications for stream corridor restoration. Earth Surface Processes and Landforms 33(6): 890–909. Betz F (2021) Biogeomorphology From Space. A Comprehensive Analysis of the Corridor of the Naryn River in Kyrgyzstan Based on Remote Sensing. Dissertation at the Catholic University Eichstaett-Ingolstadt. Betz F, Lauermann M, and Cyffka B (2020) Open source riverscapes: Analyzing the corridor of the Naryn River in Kyrgyzstan based on open access data. Remote Sensing 12(16): 2533. Bornette G and Amoros C (1996) Disturbance regimes and vegetation dynamics: Role of floods in riverine wetlands. Journal of Vegetation Science 7(5): 615–622. Bornette G, Tabacchi E, Hupp C, Puijalon S, and Rostan JC (2008) A model of plant strategies in fluvial hydrosystems. Freshwater Biology 53(8): 1692–1705. Boyle B, Hopkins N, Lu Z, Garay JAR, Mozzherin D, Rees T, Matasci N, Narro ML, Piel WH, McKay SJ, Lowry S, Freeland C, Peet RK, and Enquist BJ (2013) The taxonomic name resolution service: An online tool for automated standardization of plant names. BMC Bioinformatics 14(1): 16. Brummer TJ, Byrom AE, Sullivan JJ, and Hulme PE (2016) Alien and native plant richness and abundance respond to different environmental drivers across multiple gravel floodplain ecosystems. Diversity and Distributions 22(7): 823–835. Budde KB, Gallo L, Marchelli P, Mosner E, Liepelt S, Ziegenhagen B, and Leyer I (2011) Wide spread invasion without sexual reproduction? A case study on European willows in Patagonia, Argentina. Biological Invasions 13(1): 45–54. Caruso BS, Pithie C, and Edmondson L (2013) Invasive riparian vegetation response to flow regimes and flood pulses in a braided river floodplain. Journal of Environmental Management 125: 156–168. CBD (2010) What Are Invasive Alien Species? Convention on Biological Diversity. https://www.cbd.int/invasive/WhatareIAS.shtml. (accessed on May 16, 2021). Corenblit D, Tabacchi E, Steiger J, and Gurnell AM (2007) Reciprocal interactions and adjustments between fluvial landforms and vegetation dynamics in river corridors: A review of complementary approaches. Earth-Science Reviews 84(1–2): 56–86. Corenblit D, Baas ACW, Bornette G, Darrozes J, Delmotte S, Francis RA, Gurnell AM, Julien F, Naiman RJ, and Steiger J (2011) Feedbacks between geomorphology and biota controlling Earth surface processes and landforms: A review of foundation concepts and current understandings. Earth-Science Reviews 106(3–4): 307–331. Corenblit D, Davies NS, Steiger J, Gibling MR, and Bornette G (2015) Considering river structure and stability in the light of evolution: Feedbacks between riparian vegetation and hydrogeomorphology. Earth Surface Processes and Landforms 40(2): 189–207. Deil U (1986) Die Wadivegetation der nördlichen Tihama und Gebirgstihama der Arabischen Republik Jemen. In: Kürschner H (ed.) Contributions to the vegetation of Southwest Asia. vol. 24, pp. 167–199. L. Reichert. Deil U and Al Gifri A-N (1998) Montane and wadi vegetation. In: Ghazanfar SA and Fisher M (eds.) Vegetation of the Arabian Peninsula, pp. 125–174. Springer Science & Business Media. Deil U and Müller-Hohenstein K (1985) Beiträge zur Vegetation des Jemen I - Pflanzengesellschaften und Ökotopgefüge der Gebirgstihama am Beispiel des Beckens von At Tur (J.A.R.). Phytocoenologia 13: 1–102. Deil U and Müller-Hohenstein K (1996) An outline of the vegetation of Dubai (UAE). Verh. GfÖ 25: 77–96. Efimova AP, Shurduk IF, Kuznetsova LV, and Isaev AP (2010) River valley complexes. In: Troeva , et al. (ed.) The Far North: Plant Biodiversity and Ecology of Yakutia, pp. 225–238. Springer Science + Business Media B.V. Egger G, Politti E, Lautsch E, Benjankar R, Gill KM, and Rood SB (2015) Floodplain forest succession reveals fluvial processes: A hydrogeomorphic model for temperate riparian woodlands. Journal of Environmental Management 161: 72–82. Egger G, Drescher A, Prunier P, Gräßer L, Juszczyk I, Kudrnovsky H, Blasel L, Schönle R, and Müller N (2019a) Riparian vegetation—Surviving in an ever-changing environment. In: Muhar S, Muhar M, Egger G, and Siegrist D (eds.) Rivers of the Alps: Diversity in Nature and Culture, pp. 182–201. Bern: Haupt Verlag. Egger G, Zittel A, Juszczyk I, Resch C, Krupitz W, Resch S, Gerstner L, and Essl F (2019b) Invasive species—Distribution and strategies. In: Muhar S, Muhar A, Siegrist D, and Egger G (eds.) Rivers of the Alps, pp. 202–211. Bern: Haupt Verlag. ESRI (2010) World Major Rivers. Based on ESRI, Bartholemew and Times Books, Digital Chart of the World (DCW), U.S. National Geospatial-Intelligence Agency, NASA Earth Observatory, EROS Data Center of the U.S. Geological Survey, NASA Visible Earth, Rand McNally and Company, NASA JSC Digital Image Collection, SouthWestern Bell WorldRoom, U.S. Geological Society (Landsat). https://www.arcgis.com/home/item.html?id¼44e8358cf83a4b43bc863646cd695945 (accessed on April 12, 2021). ESRI (2016) World Mountain Ranges. Major Physiographic Regions of the Earth. Includes Mountains, Deserts, Plains and Other Landforms. https://www.arcgis.com/home/item.html? id¼da9053fa20564c92961d52f5203d3d21&view¼list#overview. (accessed on November 11, 2020). Glausen TG and Tanner LH (2019) Successional trends and processes on a glacial foreland in southern Iceland studied by repeated species counts. Ecological Processes 8(1): 1–11. Grubov VI (2010) Schlussbetrachtung zum Florenwerk Rastenija Centralnoj Azii [Die Pflanzen Zentralasiens] und die Begründung der Eigenständigkeit der mongolischen Flora. Feddes Repertorium 121(1–2): 7–13. Guðjohnsen, S.K., Magnússon, B., 2019. Útbreiðsla og flatarmál lúpí nubreiða á Íslandi 2017 (distribution of Lupinus nootkatensis in Iceland in 2017). Náttúrufræðistofnun Ísland, NÍ 19001. Available at: https://utgafa.ni.is/skyrslur/2019/NI-19001.pdf Gurnell AM (2014) Plants as river system engineers. Earth Surface Processes and Landforms 39(1): 4–25. Gurnell AM, Corenblit D, Garcia De Jalon D, González del Tánago M, Grabowski R, O’Hare MT, and Szewczyk M (2016) A conceptual model of vegetation–hydrogeomorphology interactions within river corridors. River Research and Applications 32(2): 142–163. Gut B (2008) Trees in Patagonia. Springer Science + Business Media B.V. Halik Ü, Aishan T, Betz F, Aishan T, Kurban A, and Rouzi A (2019) Effectiveness and challenges of ecological engineering for desert riparian forest restoration along China’s largest inland river. Ecological Engineering 127: 11–22. Hallsdóttir M (1995) On the pre-settlement history of Icelandic vegetation. Icelandic Agriculture Science 9: 17–29. Harmel J (2020) Invasion Strategy and Potential Distribution of Salix fragilis in Patagonia. Master thesis at University of Life Sciences and Natural Resources: Vienna. Hauer FR, Locke H, Dreitz VJ, Hebblewhite M, Lowe WH, Muhlfeld CC, Nelson CR, Proctor MF, and Rood SB (2016) Gravel-bed river floodplains are the ecological nexus of glaciated mountain landscapes. Science Advances 2(6): e1600026. Hohensinner S, Egger G, Muhar S, Vaudor L, and Piégay H (2021) What remains today of pre-industrial alpine rivers? Census of historical and current channel patterns in the Alps. River Research and Applications 37(2): 128–149. Holling CS (1973) Resilience and stability of ecological systems. Annual Review of Ecology and Systematics 4(1): 1–23. Imanbardieva N (2015) Flora and plant formations distributed in At-Bashy valleys–internal Tien Shan in Kyrgyzstan and interactions with climate. In: Öztürk M, Hakeem KR, FaridahHanum I, and Efe R (eds.) Climate Change Impacts on High-Altitude Ecosystems, pp. 569–590. Cham: Springer. Iroumé A, Paredes A, Garbarino M, Morresi D, and Batalla RJ (2020) Post-eruption morphological evolution and vegetation dynamics of the Blanco River, southern Chile. Journal of South American Earth Sciences 104: 102809. Isaev AP, Kuznetsova LV, Efimova AP, Nilolin EG, and Ermakov NB (2010) Mountain taiga. In: Troeva , et al. (ed.) The Far North: Plant Biodiversity and Ecology of Yakutia, pp. 187–193. Springer Science + Business Media B.V. Encyclopedia of Inland Waters, (2022) Author's personal copy 212 STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers Jones CG, Lawton JH, and Shachak M (1994) Organisms as ecosystem engineers. Oikos 69: 373–386. Kalníková V, Chytrý K, Bit¸a-Nicolae C, Bracco F, Font X, Iakushenko D, Ka˛ cki Z, Kudrnovsky H, Landucci F, Lustyk P, Milanovi´c Đ, ˇSibík J, ˇSilc U, Uzie˛ bło AK, Villani M, and Chytrý M (2021) Vegetation of the European mountain river gravel bars: A formalized classification. Applied Vegetation Science 24: e12542. https://doi.org/. Kamelin RV (1973) Florogenetic Analysis of the Middle Asian Natural Flora. Leningrad: Nauka 356. (In Russian). Kamelin RV (1990) Flora of Syrdarya Karatau: Materials to a Floristic Division of Middle Asia. Leningrad: Nauka 146. (In Russian). Karrenberg S, Edwards PJ, and Kollmann J (2002) The life history of Salicaceae living in the active zone of floodplains. Freshwater Biology 47(4): 733–748. Kellman MC (1970) The influence of accessibility on the composition of vegetation. The Professional Geographer 22(1): 1–4. Larson FR (1994) SRM 901: Alder. In: Shiflet TN (ed.) Rangeland Cover Types of the United States, pp. 125–126. Denver, CO: Society for Range Management. Lashchinsky NN, Kupriyanov AN, Ebel AL, and Moshkalov BM (2019) Coenoflora of ash (Fraxinus sogdiana Bunge) forests in Boralday mountains (Southern Kazakhstan). Rastitelniy mir Asiatskoy Rossii 1(33): 75–83. (In Russian). Lewerentz A, Egger G, Householder JE, Reid B, Braun AC, and Garófano-Gómez V (2019) Functional assessment of invasive Salix fragilis L. in north-western Patagonian flood plains: A comparative approach. Acta Oecologica 95: 36–44. Liendo D, Biurrun I, Campos JA, Herrera M, Loidi J, and García-Mijangos I (2015) Invasion patterns in riparian habitats: The role of anthropogenic pressure in temperate streams. Plant Biosystems-An International Journal Dealing with all Aspects of Plant Biology 149(2): 289–297. Linke S, Lehner B, Dallaire CO, Ariwi J, Grill G, Anand M, Beames P, Burchard-Levine V, Maxwell S, Moidu H, Tan F, and Thieme M (2019) Global hydro-environmental subbasin and river reach characteristics at high spatial resolution. Scientific Data 6(283): 1–23. Data available at: https://www.hydrosheds.org/page/hydroatlas. Liu D, Diplas P, Hodges CC, and Fairbanks JD (2010) Hydrodynamics of flow through double layer rigid vegetation. Geomorphology 116(3–4): 286–296. Magnússon SH, Magnússon B, Elmarsdóttir Á, Metúsalemsson S, and Hansen HH (2016) Vistgerðir á landi (Terrestrial habitats). In: Ottósson JG, Sveinsdóttir A, and Harðardóttir M (eds.) Vistgerðir á Íslandi (Habitat types of Iceland). Fjölrit Náttúrufræðistofnunar, vol. 54, pp. 17–169. Icelandic Institute of Natural History. Maier F, Rood SB, Hohensinner S, Becker I, Harmel J, Müller N, and Egger G (2022) Mountain Rivers: A global overview of river channel forms, with a focus on the distinctive braided rivers. In: Encylopedia of Inland Waters, 2nd edn Elsevier. Makaske B, Smith DG, and Berendsen HJ (2002) Avulsions, channel evolution and floodplain sedimentation rates of the anastomosing upper Columbia River, British Columbia, Canada. Sedimentology 49(5): 1049–1071. Masutomi Y, Inui Y, Takahashi K, and Matsuoka Y (2009) Development of highly accurate global polygonal drainage basin data. Hydrological Processes 23(4): 572–584. Data available at: https://www.cger.nies.go.jp/db/gdbd/gdbd_index_e.html. McGlone MS, Duncan RP, and Heenan PB (2001) Endemism, species selection and the origin and distribution of the vascular plant flora of New Zealand. Journal of Biogeography 28(2): 199–216. Meier CI, Reid BL, and Sandoval O (2013) Effects of the invasive plant Lupinus polyphyllus on vertical accretion of fine sediment and nutrient availability in bars of the gravel-bed Paloma river. Limnologica 43(5): 381–387. Mendelova M, Hein A, McCulloch R, and Davies B (2017) The last glacial maximum and deglaciation in Central Patagonia, 44 S–49 S. Cuadernos de Investigación Geográfica 43(2): 719–750. Meurk CD and Williams PA (1989) Plant Ecology of Braided Rivers of Canterbury. Report, vol. 678, DSIR Botany Division 25. Miller C (2004) Floristics and species richness of floodplain forests, South Westland, New Zealand. New Zealand Journal of Botany 42(5): 847–860. Moskalyuk T (2016) Chosenia arbutifolia (Salicaceae): Life strategies and introduction perspectives. Sibirskiy Lesnoy Zhurnal 3: 34–45. Müller N (1995) River dynamics and floodplain vegetation and their alterations under the human impact. Archiv für Hydrobiologie 101(9): 477–512. Müller N (1998) Effects of natural and human disturbances on floodplain vegetation. In: Müller N, Okuda S, and Tama N (eds.) Proceedings of the International Symposium on River Restoration, Tokyo 15–24. Müller N and Okuda S (1998) Invasion of alien plants in floodplains—A comparison of Europe and Japan. In: Starfinger U, Edwards K, Kowarik I, and Williamson M (eds.) Plant Invasions, pp. 321–332. Oxford Academic. Müller N, Wittmann A, Meurk C, Houliston G, Scheidegger C, and Stewart G (2017) Invasion of the endangered European riverbed shrub Myricaria germanica (L.) Desv. in New Zealand—traits, distribution and new ecological niche. In: 4th River Conference: Biodiversity of Alpine Rivers, Cornino, Forgaria nel Friuli, Udine, Italy, 14 May 2017 Data available at: https://www.fh-erfurt.de/lgf/fileadmin/LA/Personen/Mueller/Tagliamento/5-Mueller_2017.pdf. Natural Earth (2018) Physical Labels. Area and Point of Major Physical Features. https://www.naturalearthdata.com/downloads/10m-physical-vectors/. (accessed on November 11, 2020). Nikolin EG (2012) The flora of the Verkhoyansk range and its spatial organization. Extended abstract of Dr. Sci. (Biol.) Dissertation. Novosibirsk, 34. [In Russian]. Nikolin EG (2013) Checklist of the Verkhoyansk Range Flora. vol. 248. Novosibirsk: Nauka. [In Russian]. Nikolin EG (2014) Flora of a valley complex of the Verkhoyansk range (North-Eastern Asia). In: Baranova OG and Litvinskaya SA (eds.) Comparative Floristics: Analysis of Plant Species Diversity. Problems. Perspectives. Proceedings of 10th International Workshop on Comparative Floristics 84–95. [In Russian]. Ogureeva GN, Miklyaeva IM, Safronova IN, and Yurkovskaya TK (1999) Map ‘Latitudinal and Altitudinal Zonation of Vegetation of Russia and Adjacent Territories’ (1:8 000 000). Ekor Moskva, Moscow 2. Patzelt A (2015) Synopsis of the Flora and Vegetation of Oman, with special emphasis on patterns of plant endemism. Jahrbuch 2014 der Braunschweigischen Wissenschaftlichen Gesellschaft, pp. 282–317. Pfadenhauer JS and Klötzli FA (2014) Vegetation der Erde. Grundlagen, Ökologie, Verbreitung. Springer Spektrum 56–65. Piégay H, Grant G, Nakamura F, and Trustrum N (2006) Braided river management: From assessment of river behaviour to improved sustainable development. Braided Rivers: Process, Deposits, Ecology and Management 36: 257–275. Plachter H and Reich M (1998) The significance of disturbance for populations and ecosystems in natural floodplains. In: Müller N, Okuda S, and Tama N (eds.) Proceedings of the International Symposium on River Restoration, Tokyo 29–38. RGI Consortium (2017) Randolph Glacier Inventory—A Dataset of Global Glacier Outlines: Version 6.0: Technical Report, Global Land Ice Measurements from Space, Colorado, USA. Digital Media. Data available at: http://www.glims.org/RGI/randolph60.html Richardson DM, Pysek P, Rejmanek M, Barbour M, Panetta D, and West C (2000) Naturalization and invasion of alien plants: Concepts and definitions. Biodiversity Research 6: 93–107. Rozzi, R., Armesto, J.J., Gutiérrez, J.R., Massardo, F., Likens, G.E., Anderson, C.B., Poole, A., Moses, K.P., Hargrove, E., Mansilla, A.O., others, 2012. Integrating ecology and environmental ethics: Earth stewardship in the southern end of the Americas. Bioscience 62(3), 226–236. Rüger N, Schlüter M, and Matthies M (2005) A fuzzy habitat suitability index for Populus euphratica in the Northern Amudarya delta (Uzbekistan). Ecological Modelling 184(2–4): 313–328. Rundgren M and Ingólfsson Ó (1999) Plant survival in Iceland during periods of glaciation? Journal of Biogeography 26(2): 387–396. Safarov NM (2003) Botanico-geographical peculiarities of central Pamiro-Alay. Izvestiya Otdeleniya Boil. and Med. Nauk AN RT 1(148): 5–25. (In Russian). Schultz J (2005) The Ecozones of the World: The Ecological Divisions of the Geosphere. Springer. Schulz C and Kleinschmit B (2019) Zentralasiatische Tugai-Auwälder—Ein gefährdetes Ökosystem. Auenmagazin 15: 11–17. Sheley RL, Jacobs JS, and Carpinelli MF (1998) Distribution, biology, and management of diffuse knapweed (Centaurea diffusa) and spotted knapweed (Centaurea maculosa). Weed Technology 353–362. Spyreas G, Wilm BW, Plocher AE, Ketzner DM, Matthews JW, Ellis JL, and Heske EJ (2010) Biological consequences of invasion by reed canary grass (Phalaris arundinacea). Biological Invasions 12(5): 1253–1267. Tesch N and Thevs N (2020) Wetland distribution trends in Central Asia. Central Asian Journal of Water Research 6(1): 39–65. Encyclopedia of Inland Waters, (2022) Author's personal copy STRUCTURES AND FUNCTIONS OF INLAND WATERS - WETLANDS | Riparian Vegetation of Gravel-Bed Rivers 213 Thevs N, Zerbe S, Schnittler M, Abdusahlih N, and Succow M (2008) Structure, reproduction and flood-induced dynamics of riparian Tugai forests at the Tarim River in Xinjiang, NW China. Forestry 81(1): 45–57. Thevs N, Buras A, Zerbe S, Kuhnel E, Abdusalih N, and Ovezberdiyeva A (2012) Structure and wood biomass of near-natural floodplain forests along the central Asian rivers Tarim and Amu Darya. Forestry 85(2): 193–202. Tockner K, Paetzold A, Karaus U, Claret C, and Zettel J (2006) Ecology of braided rivers. In: Sambrook Smith GH, Best JL, Bristow CS, and Petts GE (eds.) Braided Rivers. vol. 36, pp. 339–359. International Association of Sedimentologists. Tockner K, Bunn SE, Gordon C, Naiman RC, Quinn GP, and Stanford JA (2008) Flood plains: Critically threatened ecosystems. In: NVC Polunin (ed.) Aquatic Ecosystems: Trends and Global Prospects, pp. 45–61. Cambridge University Press. Treshkin SY, Kamalov SK, Bachiev A, Mamutov N, Gladishev AI, and Aimbetov I (1998) Present status of the tugai forests in the lower Amu-Dar’ya Basin and problems of their protection and restoration. In: Ecological Research and Monitoring of the Aral Sea Deltas—A Basis for Restoration. UNESCO Aral Sea Project. Ulloa H, Iroumé A, Picco L, Vergara G, Sitzia T, Mao L, and Mazzorana B (2020) Do the morphological characteristics of Chilean gravel-bed rivers exhibit latitudinal patterns? Journal of South American Earth Sciences 99: 102522. Vidal OJ, Bannister JR, Sandoval V, Pérez Y, and Ramírez C (2011) Woodland communities in the Chilean cold-temperate zone (baker and Pascua basins): Floristic composition and morpho-ecological transition. Gayana Botánica 68(2): 141–154. Vilmundardóttir OK, Gísladóttir G, and Lal R (2014) Early stage development of selected soil properties along the proglacial moraines of Skaftafellsjökull glacier, SE-Iceland. Catena 121: 142–150. Vilmundardóttir OK, Gísladóttir G, and Lal R (2015) Soil carbon accretion along an age chronosequence formed by the retreat of the Skaftafellsjökull glacier, SE-Iceland. Geomorphology 228: 124–133. Violle C, Navas ML, Vile D, Kazakou E, Fortunel C, Hummel I, and Garnier E (2007) Let the concept of trait be functional!. Oikos 116: 882–892. Wardle P (1991) Vegetation of New Zealand. Cambridge: Cambridge University Press 360–372. Wasowicz P, Przedpelska-Wasowicz EM, and Kristinsson H (2013) Alien vascular plants in Iceland: Diversity, spatial patterns, temporal trends, and the impact of climate change. Flora 208: 648–673. Weber E (2017) Invasive Plant Species of the World. A Reference Guide to Environmental Weeds, 2nd edn. Wallingford: Oxfordshire; Boston, MA: CABI Publishing. Williams P and Wiser S (2004) Determinants of regional and local patterns in the flora of braided riverbeds in New Zealand. Journal of Biogeography 31(8): 1355–1372. Woodward J (2014) The Ice Age: A Very Short Introduction. OUP Oxford. https://doi.org/10.1093/actrade/9780199580699.001.0001. Woolmore CB (2011) The vegetation of braided rivers in the upper Waitaki basin South Canterbury, New Zealand. Canterbury Series 0211 Christchurch: Department of Conservation 67. Zong L and Nepf H (2010) Flow and deposition in and around a finite patch of vegetation. Geomorphology 116(3–4): 363–372. Further reading Maier F, Rood SB, Hohensinner S, Becker I, Harmel J, Müller N, and Egger G (2022) Mountain Rivers: A global overview of river channel forms, with a focus on the distinctive braided rivers. In: Encylopedia of Inland Waters, 2nd edn Elsevier. Encyclopedia of Inland Waters, (2022)
