Biomes of the Southern Hemisphere 3031267389, 9783031267383

Citation preview

Biome Ecology 1

Ladislav Mucina

Biomes of the Southern Hemisphere

Biome Ecology Volume 1

Series Editor Ladislav Mucina , Harry Butler Institute, Murdoch University, Perth, Australia

Biome is a large-scale biotic community and its environment, defined using functional rather than biodiversity-focused criteria of delimitation. Biotic communities are structured by drivers at various scales and levels of complexity. Most of the research in (biotic) community ecology in the past has been concentrating on fine- and mid-scales involving habitats and their complexes at landscape level. Less attention has been paid to large scales— those involving (sub)continents, hemispheres, and indeed—the entire planet. Knowing the biome structure and its origins, are becoming vital to understanding complex patterns in relation to processes operating at large scales. Such processes involve climate dynamics, land-use changes, and effects of continental- and global-level nature conservation efforts. Biomes are functional units of ecology and challenging to define and delimit because of poorly tangible nature of processes underpinning the functioning of the large-scale communities. These processes involve biomass production, nutrient cycling, disturbance, and recovery dynamics and the like. Several biome schemes are used to tackle the functionality of these large-scale units, yet there is still a lot of latitude left to formulate more scientifically robust and better formalized tools of delimitation of biomes. Not all parts of the world have a functional classification of ecosystems available. Undoubtedly, this dire situation is calling for action. More information, and more profound syntheses of the biome patterns are dearly needed. The new book series will focus on synthesizing the knowledge of distribution and origins of biomes in various parts of the world and at the planetary scale. Further, the series will offer space for development of new approaches of delimitation of biomes and new tools of using this knowledge in predictive, as well as reconstructive, modelling for the purposes of the most urgent tasks facing the mankind, such as climate change, land-use dynamics, survey of natural resources, food production, and health.

Ladislav Mucina

Biomes of the Southern Hemisphere

123

Ladislav Mucina Harry Butler Institute Murdoch University Perth, WA, Australia Department of Geography and Environmental Studies Stellenbosch University Stellenbosch, South Africa

ISSN 2948-1465 ISSN 2948-1473 (electronic) Biome Ecology ISBN 978-3-031-26738-3 ISBN 978-3-031-26739-0 (eBook) https://doi.org/10.1007/978-3-031-26739-0 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

To those who allowed me to stand on their shoulders.

Acknowledgements and Funding

I appreciate the exchange of views on many aspects of the biomes of the SH with Alessandra T. Fidelis (underground forests), Jitka Klimešová (underground forests), Christian Körner (alpine biomes), Inara R. Leal (Caatinga), Marcelo F. Simon (Cerrado) and Zhang Baiping (MEE). Matt McGlone, Peter Bellingham and Chris Lusk have contributed with discussion on several contentious issues surrounding the identity of the New Zealand biomes. The following colleagues kindly supplied less accessible literature: Sanyi Bartha, Peter Bellingham. Greg Botha, late Avinoam Danin, Karen J. Esler, Rod J. Fensham, Anni Jašková, Kim Jong-Won, Jamie Kirkpatrick, Christian Körner, Federico Luebert, Matt McGlone, Jill Rapson, Jana Peirce, Darien E. Prado, Jean-Paul Theurillat, Tom Veblen and Skip Walker. Photographs kindly contributed by Philippe Birnbaum (New Caledonia), Lohengrin A. Cavieres (Chile and Antarctica), V. Ralph Clark (Angola), Christine E. Cooper (Antarctica), Peter C. le Roux (Marion Island), Alessandra T. Fidelis (Brazil), Charo Gavilán (Tierra del Fuego), Marie and Jiri Lochman (Australian Alps, Victoria, Tasmania, Madagascar), Mervyn C. Lötter (Mozambique), Federico Luebert (Chile), Jozef Májsky (Madagascar), Daniel Montesinos-Tubée (Peru), Dagmar Mucina (Seychelles), Stani Mucina (Seychelles), Juan Paruelo (Patagonia), Valerio D. Pillar (Brazil, Argentina), Arne Strid (Patagonia) and Jean Pierre Vande Weghe (Gabon). Caley Higgs, Cameron McMains, Les W. Powrie and James L. Tsakalos kindly assisted with producing climate diagrams and maps. I thank many colleagues, too many to name, for their precious accompany during my explorations of the biomes of South America, Africa, Subantarctica, Australia, New Caledonia and New Zealand (and many other places north of the Equator). I have been logistically supported by the Iluka Chair in Vegetation Science and Biogeography at the Murdoch University, Perth, Western Australia.

vii

Contents

1 Biomes of the Southern Hemisphere: Introduction and Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Biome: What’s in the Name? . . . . . . . . . . . . . . . . . . . . 1.1.1 Biome’s Many Faces, Disguises, and Pretences 1.1.2 Azonality, Intrazonality, and Extrazonality . . . . 1.1.3 Scaling the Biome Concept . . . . . . . . . . . . . . . . 1.1.4 Ecotones in Biome Context . . . . . . . . . . . . . . . . 1.2 Southern Hemisphere in Focus . . . . . . . . . . . . . . . . . . . 1.2.1 A Hitchhiker’s Guide to the Climate of the Southern Hemisphere . . . . . . . . . . . . . . . 1.2.2 North Versus South: A Brief Story of Two Worlds . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.3 A New Look at Biomes of the Southern Hemisphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Why This Book?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Procedures and Tools to Address the Goals . . . . . . . . . 1.5 Climate Diagrams as Bioclimatic Fingerprints . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . .

1 2 2 3 3 10 10

....

11

....

13

. . . . .

. . . . .

14 15 16 16 19

2 Southern Hot Tropical Biomes . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 On Biome Classification of the Tropical Rainforests. . . . . . . 2.2 The Large-Scale Patterns in the Subtropical Rainforests . . . . 2.3 Multi-faceted Southern Seasonal Tropical Biomes . . . . . . . . 2.3.1 Heterogeneity of the Savanna Biomes: A Southern Perspective . . . . . . . . . . . . . . . . . . . . . . . 2.3.2 Madagascan ‘Savannas’: Natural or Anthropogenic? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.3 Underground Forests . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Tropical Dry Forests Revisited . . . . . . . . . . . . . . . . . . . . . . . 2.4.1 Tropical Dry Forest: What’s in the Name? . . . . . . . . 2.4.2 Typology of the Global TDF. . . . . . . . . . . . . . . . . . . 2.4.3 A Critique of the So-Called ‘Succulent Biome’. . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

23 23 26 31

. . . . . . .

. . . . . . .

. . . . .

. . . . . . .

. . . . .

31 37 40 42 42 45 56 57

ix

x

3 Southern Mediterranean-Type Ecosystems: An Extratropical Marvel . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Mediterranean-Type Ecosystems: Some Basics . . . . . . . 3.1.1 Where to Find Them? . . . . . . . . . . . . . . . . . . . . 3.1.2 What’s in the Name? . . . . . . . . . . . . . . . . . . . . . 3.1.3 Similarities, Convergence, Divergence . . . . . . . 3.1.4 Diversity Patterns . . . . . . . . . . . . . . . . . . . . . . . 3.2 Unique Features of the Southern MTEs . . . . . . . . . . . . 3.2.1 Australian ‘Mediterranean’: Home to the Most Extensive Temperate Woodland . . . . . . . . . . . . 3.2.2 The Diminished Role of Fire in the Chilean Matorral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.3 Missing Flammable Woodlands in the Cape . . . 3.2.4 Case of the Forests Left Behind: Relicts or Alternative Stable States? . . . . . . . . . . . . . . . 3.2.5 Why Are the Australian MTEs So Poor in Annuals? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Mediterranean-Type Ecosystems in the Global Scheme of Biomes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Dry Face of the ‘Wet Hemisphere’: Southern Deserts and Semideserts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Where to Find Those Arid Ecosystems, Thresholds, and Drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Australian Deserts? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Odd Ecotonal Thickets . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.1 Chaco and Espinal. . . . . . . . . . . . . . . . . . . . . . . 4.3.2 Albany Thickets . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Oceanic Coastal Semideserts: ‘Passatwüsten’ . . . . . . . . 4.4.1 Madagascan Thorny Thickets . . . . . . . . . . . . . . 4.4.2 Galapagos Coastal Semidesert . . . . . . . . . . . . . . 4.4.3 Tropical Atlantic Insular Coastal Semideserts . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contents

. . . . . . .

65 65 65 65 68 68 70

....

70

.... ....

71 73

....

74

....

75

.... ....

76 77

....

81

. . . . . . . . . .

81 84 87 87 91 92 92 94 95 95

. . . . . . .

. . . . . . .

. . . . . . . . . .

. . . . . . .

. . . . . . . . . .

. . . . . . . . . .

5 Austral Temperate Zone: Either Neglected or Misunderstood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Warm-Temperate Forests and the Southern Hemisphere . . . . 5.1.1 Where to Find Them in the Southern Hemisphere? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.2 A Comparison Between the WTF of Both Hemispheres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.3 The Southern WTZ Biomes. . . . . . . . . . . . . . . . . . . . 5.2 Oceanic Temperate Zone Recognised . . . . . . . . . . . . . . . . . . 5.2.1 Valdivian Oceanic Rainforest . . . . . . . . . . . . . . . . . . 5.2.2 The Oceanic Temperate Zone Forests of Southern Australia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.3 New Zealand Oceanic Rainforest . . . . . . . . . . . . . . . 5.2.4 Island Occurrence of the OTZ . . . . . . . . . . . . . . . . . .

99 99 103 104 105 110 113 115 116 116

Contents

xi

5.2.5 Zonoecotones Involving OTZ . . . . . . . . . . . . . . 5.3 The Austro-Nemoral Forests . . . . . . . . . . . . . . . . . . . . . 5.3.1 What is the Nemoral Zone?. . . . . . . . . . . . . . . . 5.3.2 Is There a ‘Nemoral’ Southern Hemispheric Analogue? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Tropical Montane Forest: Cold Islands in the Sea of Heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.1 Temperate Islands Within the Tropics . . . . . . . . 5.4.2 Global Variability of the TMF System . . . . . . . 5.4.3 Supranubial Tropical Belt . . . . . . . . . . . . . . . . . 5.5 ‘Boreal’ in the South? Antiboreal Rediscovered . . . . . . 5.5.1 Patagonian and Fuegian Antiboreal Biomes . . . 5.5.2 Subantarctic Antiboreal Vegetation . . . . . . . . . . 5.5.3 A Word on ‘Megaherblands’ . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.... .... ....

117 121 121

....

122

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

123 123 127 128 131 132 139 141 142

6 The Southern Steppes and Other Grassy Oddballs of the Southern Hemisphere . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Patagonian ‘Steppe’ and Semidesert . . . . . . . . . . . . . . . 6.2 The ‘Pampa-Problem’ Revisited… Again . . . . . . . . . . . 6.3 African Montane Grasslands . . . . . . . . . . . . . . . . . . . . . 6.3.1 Highveld and Manica Highland Grasslands . . . . 6.3.2 Angolan Montane Grasslands . . . . . . . . . . . . . . 6.4 Australasian Natural Grasslands . . . . . . . . . . . . . . . . . . 6.4.1 Tasmanian Tussock Grasslands . . . . . . . . . . . . . 6.4.2 Monaro Tussock Grasslands . . . . . . . . . . . . . . . 6.4.3 Bunya Grassy Balds . . . . . . . . . . . . . . . . . . . . . 6.4.4 South Island Chionochloa Grasslands . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . .

153 153 157 162 162 164 165 165 166 167 168 169

Biomes of the Coldest Corners of the World . . . . . . . . . . . Arctic and Antarctic: The Same Zonobiome? . . . . . . . . . . . . Rise and Fall of the Orobiome Concept . . . . . . . . . . . . . . . . Temperate Alpine Biomes . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.1 Temperate Alpine Biomes of the Northern Hemisphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.2 Temperate Alpine Biomes of the Southern Hemisphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.3 The Oromediterranean Conundrum . . . . . . . . . . . . . . 7.4 Alpine Biomes of the Tropics . . . . . . . . . . . . . . . . . . . . . . . . 7.4.1 Subtropical Alpine Zone: Puna & Co . . . . . . . . . . . . 7.4.2 Tropical Alpine Zone: Páramo & Co . . . . . . . . . . . . 7.5 Vegetation Belts, Timberlines, and the ‘Massenerhebung’ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.1 Exposure and Wind Shadowing by Surrounding Mountains: A Modifier . . . . . . . . . . . . . . . . . . . . . . .

173 173 175 181

7 The 7.1 7.2 7.3

181 182 183 187 188 193 194 196

xii

Contents

7.5.2 Cloud-Belt Formation and Effect on Soil Nutrient Status, Nutrient Cycling, and Carbon Residence: An Outcome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 7.5.3 Distance from the Sea: An Unresolved Problem . . . . 197 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 8 Synthesis: A New Global Zonobiome Paradigm . . . . . . . . . . . . 8.1 Basic Principles of Biome Classification: New Lessons . . . . 8.1.1 Delimitation of Biomes . . . . . . . . . . . . . . . . . . . . . . . 8.2 The Old and the New Asymmetry Paradigms . . . . . . . . . . . . 8.3 Zonoecotones: The Linking Elements of the New Global Hierarchical Biome System . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4 Further Challenges and Research Agenda . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

205 205 205 212 216 216 217

Abbreviations

(for the codes of the zonobiomes, see Chap. 1: Table 1.1) ACT ALP ANT ARC ASS AST BOR C C3 C4 CAM CB CE E GB GHBS ITCZ LGM MCE MED MEE MET N NEM NH NSW OBF OBZ OTF OTZ PAR PFZ RB S s.l.

Australian Commonwealth Territory Alpine biome(s) Antarctic biome Arctic biome Alternative stable state(s) Austro-steppe biome Boreal biome Central Plants characterised by C3 assimilation strategy Plants characterised by C4 assimilation strategy Plants characterised by CAM assimilation strategy Continental biome Central–eastern East, eastern Global biome Global Hierarchical Biome System Intertropical Convergence Zone Late Glacial Maximum Mediterranean-climate ecosystem Mediterranean (ethesial) biome Mass elevation effect (Massenerhebung Effect) Mediterranean-type ecosystem North, northern Nemoral biome Northern hemisphere New South Wales Oceanic temperate forest Oceanic boreal zone Oceanic temperate forest Oceanic temperate zone Paramo biome Polar frontal zone Regional biome South, southern ‘sensu lato’ (in broad sense) xiii

xiv

s.str SAV SAVa (sava) SAVm (savm) SAZ SE SH SHPB STE SUB SW TAZ TDF TMF TMZ TRO W WTF WTZ WWD ZB ZE

Abbreviations

‘sensu stricto’ (in narrow sense) Savanna biomes Arid savanna Mesic savanna Subtropical alpine zone South-eastern Southern Hemisphere Subtropical high-pressure belt Steppe biome Subtropical rainforest South-western Tropical alpine zone Tropical dry forest Tropical montane forest Tropical montane zone Tropical rainforest West, western Warm temperate forest Warm temperate zone Western wind drift, Westerlies Zonobiome Zonoecotone

1

Biomes of the Southern Hemisphere: Introduction and Approach

This is a story of the biomes of the Southern Hemisphere. It is not meant to be an exhaustive account of all sorts of large-scale biotic communities (hence ‘biomes’) found south of the Equator but rather an analysis of the geographical uniqueness of the Southern Hemisphere translated into unique biome patterns. This book will focus on zonobiomes and their low-ranked subunits called global biomes (see Mucina 2019). The azonal biomes (e.g. those of aquatic, wetland, saline, nutrient-poor environments) are also very diverse in the Southern Hemisphere (see Mucina et al. 2006b, c; Macintyre and Mucina 2022 for selected three tips of an iceberg). Therefore, they deserve separate dedicated reviews. Few biomes are shared between the Northern and Southern Hemispheres. These include tropical and subtropical rainforests, savanna woodlands and grasslands, deserts and semideserts, ethesial (mediterranean-type) woodlands, and warm-temperate forests. Because of the differences in the assembly of the floras and faunas of the respective hemisphere, we shall learn soon that there are some fundamental differences in climatic drivers and resulting climatic zoning between both hemispheres. For instance, despite their common functional traits, the savannas of the Southern Hemisphere are different from those of the Northern Hemisphere, with the former being more diverse and mesic. The deserts and semideserts of the Southern Hemisphere are older and species richer than their Northern Hemisphere counterparts. The mediterranean-

type shrublands and woodlands of the Southern Hemisphere, albeit less extensive, preserve more ancient plant and animal lineages than those of the Northern Hemisphere; they also support the species-richest temperate floras of the world. The Southern Hemisphere lacks the extensive Boreal, Nemoral, and Steppe biomes as they are known to science from the Northern Hemisphere, covering most of North America and Eurasia. Nevertheless, the ‘boreal’, ‘nemoral’, and ‘steppe’ conditions are not entirely alien to the Southern Hemisphere. Among the diverse azonal biomes, the Northern Hemisphere is home to extensive pelobiomes (bog and mire wetlands) known to be rare in the Southern Hemisphere. On the other hand, the Southern Hemisphere is home to the very extensive terrestrial peinobiomes (biotic communities dominated by nutrient-poor terrestrial environments) on our planet. I shall review the current state of knowledge of the biomes of the Southern Hemisphere using the zonobiome framework as introduced to the biome science by Walter (1976a, b; see also Walter and Box 1976; Breckle and Rafiqpoor 2019; Mucina 2019). I shall do so using a global perspective, relying on the most influential biome-ecology works, but I plan to view those classical sources of wisdom with caution and criticism. I shall subsequently ask and analyse provocative questions, identify the lingering or emerging problems, and summarise supportive and contradictory evidence and ideas, shedding some explanatory light upon those problems.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 L. Mucina, Biomes of the Southern Hemisphere, Biome Ecology 1, https://doi.org/10.1007/978-3-031-26739-0_1

1

2

1

Finally, wherever possible, I would offer some solutions. I will strive for a balance of views, but some issues might remain ill-balanced and open to new interpretations. I am more interested in revealing controversies than dishing out ready meals as I believe that recognising and formulating reasonable hypotheses is as essential as testing them. First, I shall introduce two crucial protagonists —the concepts of biome and of the Southern Hemisphere.

1.1

Biome: What’s in the Name?

1.1.1 Biome’s Many Faces, Disguises, and Pretences There have been many ways biome ecologists recognised biomes. Mucina (2019: Table 1) presented a summary of approaches. Table 1.2 here expands on this overview, mainly by adding new sources. Biomes (at any level of complexity —see Sect. 1.1.2 below) are ecosystems that are notoriously known for fuzzy boundaries and continuous transitions. Because biomes are functional units of organisation of nature, they are challenging to be delimited simply because functional variables are hardly tangible. It is, therefore, not surprising that many researchers chose surrogates to delimit biomes. Physiognomy of the dominating vegetation formation is a widely used surrogate (Table 2.1: physiognomy), in the belief that this surrogate captures the essence of the functionality of an ecosystem to be distinguished as a biome. As Mucina (2019: Fig. 3) notes, vegetation physiognomy might not always be informative to meet the goal. Some use biogeographical units (biochoria) in the belief that they reflect ecological functionality—see the discussion between Procheş (2020) and Mucina (2020). This approach is hardly recommendable simply because the criteria biochoria derived from are fundamentally different from those for biomes. There have been several interesting efforts to include functional surrogates (e.g. lifeforms, biomass, functional-trait selections), sometimes in modelling (Conradi et al. 2020).

Biomes of the Southern Hemisphere …

The problem with these approaches, albeit logically constructed, is usually a lack of appropriate large-scale spatial data. Finally, using climate characteristics or rather climate-classification systems (Table 2.1: ‘climate (only) approach’), sometimes combined with soil and hydrological variables is yet another viable approach due to the importance of climate drivers in shaping the biotic communities at large spatial and temporal scales. Here the climato-genetic criteria are particularly promising. The term ‘genetic’ refers to the origins of the patterns of the bioclimatic variables involved in biome delimitation. The origin of the biome drivers, be it climatic or soil or hydrological nature, matters. For instance, precipitation patterns are a result of macroclimatic, global-scale phenomena associated with wind and rain-bearing systems, underpinnings of temperature dynamics, and the like. Box (2016) presented a short yet comprehensive review of the climatic classifications based on the ‘genetic’ (I prefer the term ‘climato-genetic’) criteria. Box (l.c.) also calls Walter’s approach explicitly ‘genetic’ (= based on the mechanisms that generate different climate types) and refers to Walter (1955). Labelling a bioclimatic system as ‘genetic’ would mean that processes generating the patterns matter of utmost. However, this is not the case in Walter (1955) or his later seminal works (Walter 1976b; Walter and Box 1976) since all these works are about patterns rather than processes. Therefore, I recognise Box (2016) as the original source emphasising, although not yet fully implementing, climatogenetic criteria in the delimitation of the Walterian zonobiomes (see the case of the WTZ and OTZ; Chap. 6, Sects. 6.1 and 6.2, resp.). Indeed, if relevant detailed and spatially explicit data on ecosystem functionality are scarce, surrogates may provide the ‘next best thing’. Still, the temptation of expanding the meaning of the term biome into various conflation directions is well alive. Besides the mixing up the phytochorial and ecological concepts (see Table 2.1: ‘species distribution coincidence’ and well as Olson et al. 2001; Dinerstein et al. 2017 etc.), some authors would include, under the biome umbrella for the sake of comparative

1.1 Biome: What’s in the Name?

analyses, also landscape-ecological schemes such as land-use typologies (e.g. Fischer and Walentowitz 2022). Effectively, I have abandoned the original Walter’s nine-member zonobiome scheme (zonobiomes I through IX)—its coding and naming—and here introduce a new system called Global Hierarchical Biome System (GHBS). The presentation of this system—one of the significant outcomes of this treatise—in this chapter (Table 1.1) might seem untimely. However, it appears imperative to introduce the conceptual and terminological normative at this early stage to assure consistency as the development of this system will take place in the subsequent chapters of this book.

1.1.2 Azonality, Intrazonality, and Extrazonality The terms zonal, azonal, extrazonal, and intrazonal biomes have been poorly covered in English-written literature. Since I use them profusely, I wish to provide a simple explanation. The zonal biomes are those where the primary pattern and dynamics drivers are climatic (e.g. Schimper 1903; Walter 1954). The zonal biomes occupy exclusive bioclimatic and geographic spaces (Fig. 1.1a). The patterns and dynamics of the azonal biomes are primarily driven by nonclimatic factors, such as soil and hydrology (see Mucina 2019: 101; Macintyre and Mucina 2022: Table S2). Azonal biomes can rarely be found in compact, large-scale units (but see the Brazilian Pantanal or Namibian Etosha Pan). More often, they occur in the form of small-scale patches scattered across one or several zonal biomes. The nature of the link between these azonal patches and the zonal biomes determines if we are dealing with true azonality, extrazonality or intrazonality. In the case of true azonality, the azonal biome is embedded within at least two azonal biomes (Fig. 1.1b). If the patches of a zonal biome (Fig. 1.1c: patches of ZB 2) are scattered within the realm of another zonal biome, usually because regional or local climatic conditions of the latter simulate the climate of the former. If an azonal

3

biome (in a broad sense) is found exclusively within the bioclimatic envelope of one zonal biome, this azonal biome is considered intrazonal (Fig. 1.1d). The concepts of azonality are scaledependent and therefore retain validity only within the given rank of the biome hierarchy (Fig. 1.2).

1.1.3 Scaling the Biome Concept A biome is a large-scale ecosystem comprising a biotic community and its environment. The term was coined by Clements (1916) for the first time as an alternative to the broadly conceived concept of a ‘biotic community’. As shown by Mucina (2019), however, only later (Shelford 1945), the use of this term was limited to large spatial scales, giving the concept a new meaning and a certain degree of terminological uniqueness. As each ecosystem occurs in space and time, it cannot escape the vagaries of spatial and temporal scaling. This scaling dependency necessitates the presentation of biomes’ spatial and temporal variability in the form of hierarchically embedded unit systems. As reviewed by Mucina (2019) and formalised by Mucina et al. (2022a, b), four spatial tiers are distinguished: zonobiome (ZB), global biomes (GB), continental biomes (CB), and regional biomes (RB). In the sequel, I shall revisit the definitions of these hierarchical scales in terms of their link to the ecological drivers of the 1st and 2nd Orders. Zonobiome (ZB) The overarching driver of biotic patterning and functioning on our planet is solar energy—its distribution in space and time. A zonobiome is a biome occupying bioclimatic space defined primarily by thermic conditions (position of the thermal zone) in combination with unique precipitation conditions (amount and seasonality). Both thermal (hence energy the zone receives) and precipitation conditions are a result of unique climato-genetic drivers (climate-shaping processes) operating at the global scale, hence across continents, in the case of terrestrial biomes of course. Walter et al. (1975) distinguished nine ‘major climatic zones’. Although the ‘climatic

4

1

Biomes of the Southern Hemisphere …

Table 1.1 The new zonobiome system ZB

Abbr.

Name

E1

TRO

Equatorial Zone

E2

SAV

Tropical Seasonal Zone

Macroclimatic drivers

Climatic diagnosis

Synonyms and corresponding concepts

Constant high temperature; dynamics of the ITCZ

Equally warm all-yearround; frost is rare and occurs only in marginal subtropical regions; allyear-round

Walter (1976a, b: Zonobiome I)

Constant high temperature; ITCZ disturbances; rainbearing monsoons

Warm all-year-round but cooler at low; precipitations occurring throughout the year but distinctly wetter in summer

Walter (1976a, b: Zonobiome II)

Tropical Zonobiomes

Subtropical Zonobiomes S1

MED

Ethesial Zone

Yearly tug-of-war (N–S/S– N) between the semistationary ridging highpressure systems (STHP) and the Westerlies

Distinctly regular alternation of dry hot summers and wet cool winters

Walter (1976a, b: Zonobiome IV)

S2

DES

Hot Arid Zone

Domination of the STHP for the most part of the year

Warm to very hot summers and ooler winters; poorly predictable rainfall events, dry all-year-round, experiencing winterrainfall on edges towards S1

Walter (1976a, b: Zonobiome III)

B1

BOR

Boreal Zone*

Shifting dynamics of cold polar air masses; combined with maritime influence on edges

Cool summers; severe cold winters; summer rainfall

Walter (1976a, b: Zonobiome VIII)

B2

OBZ

Oceanic Boreal Zone

Shifting dynamics of cold polar air masses; combined with maritime influence; strong Westerlies

Cool summers and cold winters; high rainfall especially in winter

Mucina et al. (2023a, b: Zonobiome XII)

Walter (1976a, b: Zonobiome VI)

Cold Temperate Forest Zonobiomes

Temperate Forest Zonobiomes T1

NEM

Nemoral Zone*

Weakened Westerlies due to continental effect and weakened temperate monsoon

Warm summers; frosty winters; no true dry season, precipitation maximum in summer

T2

ANE

AustroNemoral Zone#

Weakened Westerlies due to rainshadow effect

Mild summers and winters; aseasonal precipitation, lower than in ZB T6

T3

WFZ

WarmTemperate Zone

Summer dynamics of the STHP underpinning the rain-bearing summer monsoons and extratropical cyclones

Warm to hot summers, mild winters; weak dry season; precipitation maximum in both boreal and austral summer

Walter (1976a, b: Zonobiome V); Box (2016: zonal biome Ve); Breckle and Rafiqpoor (2019: SubZonobiom an den Ostseiten der Kontinente) (continued)

1.1 Biome: What’s in the Name?

5

Table 1.1 (continued) ZB

Abbr.

Name

Macroclimatic drivers

Climatic diagnosis

Synonyms and corresponding concepts

T4

OTZ

Oceanic Temperate Zone

Strong influence of rainbearing Westerlies on both hemispheres

Mild summers and cool winter; all-yar-round rainfall, with maximum in both boreal and austral winter

Box (2016: zonal biome Vm); Breckle and Rafiqpoor (2019: SubZonobiom an den Westseiten der Kontinente); Mucina et al. (2022, 2023a, b: Zonobiome X)

T5

TMZ

Tropical Montane Zone

Temperature lag along ascending elevation and wind-bearing trade-winds

Warm-temperate thermic climate; All-year-round moist air; precipitation maxima at high sun

Earlier incorporated in ZB I

G1

STE

Northern Steppe Zone*

Weakened rain-bearing systems/large yearly temperature amplitudes

Warm summers; very cold and dry winter

Walter (1976a, b: Zonobiome VII p.p.)

G2

CON

Cold Continental Zone*

High thermal continentality; Strong regional rain shadows

Dry year-round; sporadic rain; cold winters

Walter (1976a, b: Zonobiome VII p.p.); Breckle and Rafiqpoor 2019: ‘Sub-Zonobiom der Mittelasiatischen Wüsten + Sub-Zonobiom der Zentralasiatischen Wüsten’)

G3

AST

AustroSteppe Zone#

Rained-out Westerlies (rain shadow effect); adiabatic temperature increase

Cool summers and cold winters; low winter rainfall

Walter (1976a, b: Zonobiome VII p.p.)

A1

ARC

Arctic Zone*

Polar night (boreal winter) and formation of polar cold masses; elevation-related temperature decrease

Cold and short summers; severe cold winters

Walter (1976a, b: Zonobiome IX p.p.)

A2

PUN

Subtropical Alpine Zone

High-elevation temperature lapse; influence of STHP

Warm during the day; cold (often freezing) in the night; low to extremely precipitation focused on high-run period of the year (on respective hemisphere)

Walter and Box (1976: tentative ‘zonobiome X’ on a map); Breckle and Rafiqpoor (2019: ‘SubZonobiom der Kalten Hochplateauwüsten von Tibet und Pamir’)

A3

PAR

Tropical Alpine Zone

High-elevation temperature lapse; influence of ITCZ

Warm during the day; cold (often freezing) in the night; no yearly temperature or precipitation seasonality; bimodal (high-sun) precipitation peak due to ITCZ crossing the Equator twice

Breckle and Rafiqpoor (2019: Orobiom I)

Temperate Grassland Zonobiomes

Alpine Zonobiomes

(continued)

6

1

Biomes of the Southern Hemisphere …

Table 1.1 (continued) ZB

Abbr.

Name

Macroclimatic drivers

Climatic diagnosis

Synonyms and corresponding concepts

A4

ANT

Antarctic Zone#

Polar night (austral winter) and associated formation of polar cold and dry masses

Cold dry summers and very cold dry winters

Walter (1976a, b: Zonobiome IX p.p.)

Abbr. Informal abbreviation code of a zonobiome. The zonobiomes occurring only in the NH are indicated by an asterisk, while whole exclusive to the SH are indicated by #. The codes including the letter E refer to the zones around the Equator; those including S refere to the Subtropics or rather the regions around the Tropics of Cancer and Tropics of Capricorn; those containing B refer to cold temperate regions know as boreal in the NH and anti-boreal in the SH; the letter T is involved in zones typically supporting temperate forests; the letter G introduces zones dominated by zonal grasslands, and the letter A refers to alpine zones—those occurring above the timberline as well as the Arctic and Antarctica, occurring beyong the Arctic and Antarctic Circles

zone’ concept per se was not explicitly defined by its author, it is apparent that the zones have been defined using thermic and precipitation criteria. Later, Walter (1976b) coined the term ‘zonobiome’, which was equated to ‘zone’. Mucina et al.’s (2022a, b) definition of zonobiome recognised thermic conditions as the first trier driver but fell short of explicitly including hydric patterns (precipitation amounts and precipitation seasonality). Temperature/energy and precipitation at the global scale are the drivers of the 1st Order. Hence, the distinction among the zonobiomes is underpinned by the combinations of the drivers of the 1st Order. The Tropical Diurnal Zone (zonobiome I) (Walter 1970; Walter and Box 1976), broadly overlapping with the concept of Equatorial Zone (zonobiome E1) of the new GHBS as defined in this book, are prime examples of zonobiomes. Global Biome (GB) In the Schimper-Walterian conceptual framework, temperature and water are two major ecological factors structuring and driving life on our planet. Within the zonobiomes, energy (the lead driver) and precipitation (the primary source of water) structure the terrestrial biotic communities. The zonobiomes vary along these two major gradients, and this variation can be captured in the form of subordinate units comprising

the zonobiome. Suppose a zonobiome covers a broad spectrum of biomes characterised by arid conditions on the one hand and mesic (wet) conditions on the other. One can distinguish arid vs mesic/wet zonobiome sub-units in that case. Walter’s system uses the lessinformative term ‘sub-zonobiome’ for this level. In the GHBS, these are recognised as global biomes. The resulting biotic communities tend to recur if the same or very similar conditions occur on different continents. The distinction between the global biomes is underpinned by the variability of the drivers of the 1st Order. Due to fundamental bioclimatic differences between the Northern and Southern Hemispheres (see Sect. 1.2 below), the position in the respective hemisphere can also be used as a source of recognition of hemispheric global biomes. The examples of the global biomes include, for instance, GB Mesic Savanna and GB Arid Savanna, both members of the ZB E2 (Tropical Seasonal Zone, capturing the precipitation contrast between these two GBs. The GB Tropical Rainforest and GB Subtropical Rainforest represent two global biomes that capture the thermic differences between tropical and subtropical rainforests. Finally, GB Northern Ethesial Biome and GB Southern Ethesial Biome are examples of geographically (hemispherically) defined global biomes.

1.1 Biome: What’s in the Name?

7

Table 1.2 Tools of delimitation (construction and prediction/retrodiction) of biomes and related large-scale biotic communities. Approach

Criteria of delimitation

References

Physiognomy

Appearance of vegetation (combination of growth forms)

Grisebach (1872), Küchler (1949), Fosberg (1961), Ellenberg and Mueller-Dombois (1967), UNESCO (1973)

Climate (only)

Using temperature and precipitation (expressed by of various indices) as predictive of biome patterns

Merriam (1894), Köppen (1900), Thornthwaite (1933), Holdridge (1947), Whittaker (1970), Hobbs and McIntyre (2005), Schultz (2005), Rivas-Martínez et al. (2011), Navarro and Molina (2021)

Physical environment

Combined climate (zonal units) and soil/water (azonal units) as drivers of biome patterns

Schimper (1898), Walter (1954)

Functional-ecosystem modelling

Net Primary Productivity, NDVI, and related production-focused ecosystem characteristics to model biomes

Lieth (1964), Paruelo et al. (2001), Scheiter et al. (2013), Higgins et al. (2016)

Species distribution coincidence

Basically suggests that biomes are the same as phytogeographic units

White (1983), Crisp (2006), EMPRABA (www.empraba.br)

Physical environment + PFTs + physiology (+ biochemical cycles)

classical equilibrium-coupled and DVGM biome modelling (incl. modelling involving biochemical fluxes)

Box (1981), Prentice et al. (1992), Kaplan et al. (2003), Sitch et al. (2003)

Physical environment + disturbance

Combined climate, soil/water and large-scale disturbance as drivers of biome patterns

Dublin et al. (1990), Bond (2005), Rutherford et al. (2006a, b, c)

Eclectic

Biome defined as lump-sum of ecoregions that were defined using manifold (often obscure) classification criteria

Olson et al. (2001), Dinerstein et al. (2017)

Human impact

Specific to arthromes defined as human constructions (arable fields, timber plantations, human settlements and land communication structures)

Ellis and Ramankutty (2008)

Vegetation units

Using vegetation-classification (and spatial mapping) units as surrogates informing on ecological underpinning (and implicitly on ecosystem functionality) and evolutionary assembly

Roy et al. (2006), Rutherford et al. (2006a, b, c), Mucina (2013), Macintyre and Mucina (2022), Mucina et al. (2022, 2023), Luebert et al. (2023)

Physical environment + functional traits + evolutionary assembly

Linking current and past patterns in a comprehensive macroevolutionary and macroecological framework

Moncrieff et al. (2016)

Modelled distribution of species + life form

Searching for spatial concentration (using large set of modelled species distributions and their associated dominating life forms

Conradi et al. (2020)

(continued)

8

1

Biomes of the Southern Hemisphere …

Table 1.2 (continued) Approach

Criteria of delimitation

References

Ecological drivers

[Functional biome] ‘united by one or a few common major ecological drivers that regulate major ecosystem functions and ecological processes’; more detailed information on those major ecological drivers is, however, missing

Keith et al. (2020, 2022)

Modelled distribution of species + life form + phylogenetic patterns

Attempt at integration of biogeographical, ecological and evolutionary underpinnings

Cardoso et al. (2021)

Selective consensus

Superimposing selected ‘biome schemes’; many are not featuring biomes, but othee types of typologies (biogeography, landscape type)

Beierkuhlein and Fischer (2021), Fischer and Walentowitz (2022)

The term ‘physical environment’ includes climate, soil, and hydrological characteristics. Based on Mucina (2019: Table 1, modified and expanded). The ‘Approaches’ in this table are in ascending order of the first publication which was suggesting the new approach. The Approaches using functional elements (or their surrogates) are highlighted in bold

ZB1 A1

A

ZE 1-2

A2

ZB2

(A) zonality

(B) azonality

(C) extrazonality

(D) intrazonality

Fig. 1.1 Zonality and azonality explained. A: Zonality: Two zonobiomes (ZB1 and ZB2; blue and green, resp.) occupy exclusive bioclimatic and geographic spaces. They create a zonoecotone (ZE) in a region showing transitional bioclimatic characteristics. b: Azonality: An azonal biome (a; red) is found in the form of scattered patches across two zonobiomes. c: Extrazonality: patches of ZB2 are found scattered within the bioclimatic realm of

ZB1. These patches are found in refugial areas characterised by the same/similar bioclimate as the main distribution region occupied by the ZB2. d: Intrazonality: The azonal biome A is subdivided into subunits A1 and A2. Each occurs exclusively within the region of the zonobiomes ZB1 and ZB2, resp. These subunits are called ‘intrazonal’ of units of the zonobiome rank

Continental Biome (CB) The energy distribution and its translation into temperature zones on our planet are dependent on cosmic circumstances (distance of Sun to Earth, dynamics of the Earth axis inclination), which then, in turn, determine the temperature

zoning. The temperature immediately affects precipitation patterns, which vary across continents. The 1st Order drivers become modified by the idiosyncrasies of the continents' position, size, and shape. The global biomes are found on various continents, subject to variations in the

1.1 Biome: What’s in the Name?

ZB GB CB RB

9 [1] Pedobiome 1 [2] aRB / intCB / intGB / intZB

[4] intRB / intCB / intGB / intZB

[5] aGB / intZB

[3] aCB / intGB / intZB

[6] Azonal

Fig. 1.2 Hierarchical view of the zonality and azonality. The prefixes to the (low-case) codes preceding the ZBs, GBs, CBs, and RBs indicate the azonal (a) or intrazonal (int) position. The position of the Biome [2] could be, as an example interpreted as azonal at the RB level

(aRB) and intrazonal at the CB, GB, and ZB levels (intCB, intGB, intZB, respectively). The Biome [6] is considered azonal since it straddles two different zonobiomes, while the Biome [5] is azonal at the GB level (aGB), however intrazonal on the ZB level (intZB)

energy-water interactions, manifested in different climato-genetic systems producing convergent biotic patterns at the sub-continental and continental scales. These climato-genetic systems drive patterns and dynamics of continental biomes (see Mucina 2019), which are subsets of global biomes. The distinction among the continental biomes is underpinned by the bioclimatic idiosyncrasies emerging on various continents (and oceanic archipelagos) through modification of the drivers of the 1st Order. CB Cerrado, CB Southern African Mesic Savanna, and CB Australian Eucalyptus Savanna are examples of continental biomes falling within the brackets of GB Mesic Savanna.

modified by local/regional (intracontinental) modifiers, such as orographic effects on precipitation, elevational effect on temperature, and the like. I call these the drivers of the 2nd Order. At this biome scale, the quality of substrate (regional geology and associated soil patterns, hydrology), also creating azonal situations, can be incorporated. This de facto means that the regional biomes can be of zonal or azonal nature (pedobiomes). This book addresses regional biomes occasionally since many continental biomes in the Southern Hemisphere show complex variability deserving attention in more detail as, for instance, done by Mucina et al. (2022, 2023a). The latter source offers several good examples of zonal regional biomes, such as AF2 Southern Mistbelt Forest, TDFa2 Southern African Dry Forest, and azonal regional biomes, such as ARF3 Cape Riparian Forest, and AMAN2 Tropical Indian Ocean Mangrove. All are characterised by unique bioclimate, soils, and hydrology.

Regional Biome (RB) Continental biomes can be subdivided into regional biomes. As in all the upper-ranked biomes at the ZB, GB, and CB levels, the drivers of the 1st Order are fundamental in defining their bioclimatic envelopes. These are, however, further

10

1.1.4 Ecotones in Biome Context Biomes at all levels of the hierarchy (with a notable exception of the regional biomes; see Mucina et al. 2022, 2023a) are distinguished by climatic differences. Climatic variables are notoriously continuous, and therefore challenging to chop the climatic gradients into create discrete bins and, consequently, define crisp spatial borders amenable to capture on maps. Indeed, bar regional biomes where soil and hydrological variables can sometimes create very well-defined and sharp borders, the borders between ZBs, GBs, and CBs are fuzzy (vague). The definite lines, representing the borders of biomes, are only of an approximate, symbolic value and represent an ecotone of varying breadth and steepness. More realistically, the zones/regions where two biomes meet show patterns often called mosaics and transitional zones. However, both concepts make sense only at specific spatial (and temporal) scales and in situations where the elements (biomes) are transiting into each other or creating a mosaic when the constituent elements are clearly defined (see Mucina et al. 2006a: 16–17). Biome ecology, most notably Walter's zonality/azonality framework, recognises socalled zonoecotones when transitional patterns involve two (rarely three) distinct zonobiomes. In general terms, zonoecotone is a general term encompassing the concepts known as ecotone and ecoclines (van der Maarel and Westhoff 1964; van Leeuwen 1965, 1966; Gosz 1993). These concepts are rooted in the so-called ‘Relation Theory’ coined by van Leeuwen (1965, 1966; see also van der Maarel 1976, 1990; de Jong et al. 2015), which addresses, according to its author, fundamental system relations. Applying this theory to environmental boundary situations, such as boundaries between biomes, yielded two types of boundaries called limes convergens and limes divergens, reflecting spatial concentration and dispersion, respectively, of the system elements. In the case of the limes convergens between two vegetation types (or biomes), the transition is coarse-granulated and sharp (van Leeuwen 1966) and forms, at a given

1

Biomes of the Southern Hemisphere …

spatial scale, a mosaic of vegetation types (see Fig. 1.3a). Van Leeuwen (1966) also suggested calling this transition between two ecological systems an ecotone (in the strict sense) (van der Maarel 1990). A limes divergens, on the contrary, shows a fine pattern granulation, and overall it is a gradual transition zone (see Fig. 1.3b). Van der Maarel and Westhoff’s (1964) term ecocline describes this ecological transition situation well. Naturally, these two types of boundaries have different ecological and historical drivers at different scales of biome complexity. In other words, a boundary between two regional biomes of the same zonobiome can be convergent, while the boundary of the same zonobiome with another can be divergent. In rare cases, the ecotonal space between two zonobiomes can be very extensive (Fig. 1.3c). Here new biomes, matching perhaps best the continental and regional biome levels of complexity, can form and persist over an extended time. The South African Albany Thicket biome (see Chap. 5, Sect. 5.3.2; also Hoare et al. 2006) might be an example of such a situation.

1.2

Southern Hemisphere in Focus

Panta rei—all things are in flux—and so is the advent and demise of biomes on geologic time scales. The assembly of biomes of the Southern Hemisphere along evolutionary times scales is intriguing, engaging, and equally complex. Some biomes (tropical rainforest, savanna, tropical dry forest) have received much attention from palaeobotanists and palaeogeographers. The others, especially the temperate forests and grasslands, has not been paid as much attention, unfortunately. It is beyond the scope of this overview to attempt a summary of what we have learned about the evolution of the Southern Hemisphere biomes until now. Still, in those cases where comprehensive data and intriguing hypotheses pertinent to the evolutionary assembly of biota are of obvious relevance to the biome system being developed and presented in this work, then the evolutionary processes underpinning the patterns of those biomes will be discussed.

1.2 Southern Hemisphere in Focus

11

A: Ecotone s.str. (limes convergens)

B: Ecocline (limes divergens)

C: Zonoecotonal origin of a new biome

Fig. 1.3 Typology of ecotones (a, b) and zonoecotonal origin of a new biome. a (ecotone in a narrow sense): two biomes (red: grassland, blue: forest meet min the ecotone (the middle third of the image) where the forest biome forms a well-defined (crisp borders) mosaic with the grassland biome. b (ecocline): two biomes (blue and red) intergrade continuously, forming a fine-grained ecotone

sharing characteristics (environmental and vegetation structural as well as floristic ones) of both biomes. c The very broad and persistent (over long periods) ecotone develops its own unique set of environmental characteristics leading to the formation of a qualitatively new biome

Understanding the distribution of zonal biomes in the Southern Hemisphere requires understanding the complex drivers shaping the climate of this part of the world and appreciating the differences between the hemispheres.

summarise the major climato-genetic drivers of the movements of air masses, precipitation, and heat distribution. The Southern Hemisphere is home to three major continents (South America, Africa, and Antarctica), one smaller continent (Australia), and at least two microcontinents, namely Madagascar and Zealandia. The latter is heavily fragmented and surviving the ever-turning tectonic continental machine in form of fragments known as New Zealand, New Caledonia, and Norfolk Island. In addition, thousands of islands in the Pacific, Southern Atlantic, Indian and Southern Oceans add more firm land to support vegetation. Seven significant protagonists are involved in shaping the climate of the Southern Hemisphere: (1) the tilt of the Earth Axis and associated energy distribution spanning the Southern Pole

1.2.1 A Hitchhiker’s Guide to the Climate of the Southern Hemisphere Because the climate is the prime driver of the global, hemispheric, and continental vegetation formation patterns defining biomes, this section shall set the scene and aims to present summaries of the major climatic systems shaping the biota of the continental and microcontinent masses on the Southern Hemisphere. Here, I shall

12

and the Equator and, as such, defining the temperature zones, (2) the dynamics of the InterTropical Convergence Zone (ITCZ), (3) Subtropical High-Pressure Belt (SHPB) and associated dynamics of the Hadley Cells, (4) southern monsoonal systems, (5) the Westerlies (Western Wind Drift; WWD), (6) Circumpolar Trough (Polar Easterlies), and, finally, (7) sea surface temperature, oceanic currents and associated upwellings. The climate of the equatorial Tropics is dominated by the dynamics (expansion and contractions around the Equator) of the ITCZ. This zone of moisture-laden clouds originates through the convergence of rain-bearing SE Trade Winds from the Southern Hemisphere and the NE Trade Winds from the Northern Hemisphere. The moisture rains out within the bounds of the ITCZ, and the warm, dry air ascends at high altitudes, to be later recycled in the ethesial latitudes (see below). The rainfall occurs in wet Tropics throughout the year. It feeds the lush, wet, and species-rich tropical (at the extreme southernmost positions of the ITCZ in the Southern Hemisphere) and the subtropical rainforests (all zonobiome E1; for the codes of the zonobiomes consult Table 1.1). In regions where the ITCZ’s regular oscillation is compromised, or ITCZ reaches only marginally, year-round rainfall does not materialise, and dry season(s) emerge. Here are the vegetation formations of zonobiome E2 (tropical seasonal zone), including savannas and tropical dry forests. The precipitation patterns in the Pacific Tropics are further modified by the El Niño–Southern Oscillation (ENSO)—a cycle of warm and cold sea surface temperature (SST) of the tropical central and eastern Pacific Ocean, which creates precipitation-rich and precipitation-poor (depending on the region), lasting several years. Similar systems associated with the SST also develop in the northern Indian Ocean (Indian Ocean Dipole) and the equatorial Atlantic Ocean. The Subtropical High-Pressure Belt is a series of high-pressure cells created by the descending air that originated in the Tropics. This dry air is heated adiabatically in subtropical latitudes (roughly around the Tropic of Capricorn (in the

1

Biomes of the Southern Hemisphere …

Southern Hemisphere). The high-pressure systems prevent rain-bearing winds from penetrating the regions and give rise to zonal hot arid zone— deserts and semideserts of the zonobiome S2. The climate of the temperate regions of the Southern Hemisphere is dominated by the WWD. In the Southern Hemisphere, the Westerlies are the primary climatic phenomenon within the latitudes 30° and 60° S. They carry much moisture, which they download especially on windward slopes of mountains (Andes, Australian Alps, Central Plateau of Tasmania, Southern Alps of New Zealand) and archipelagos of islands in the Southern Ocean. The WWD is the underpinning driver of the occurrence of formations of the zonobiome T4 (oceanic temperate forests) in the cool temperate zone. Reaching to the South, into the cold-temperate zone, they also control the occurrence of formations of the zonobiome B2 (oceanic boreal zone). In rain shadows on the leeward slopes of the mountains obstructing the WWD, the AustroNemoral (zonobiome T2) and Austral Steppe (zonobiome G3) biomes are formed. In the austral winter season, the WWD also expands north under the Antarctic vortex—a stratospheric wind system associated with a low-pressure system called Circumpolar Trough). Here, at the edge of the subtropics, WWD partly replaces the weakening Hadley Cells. These egain their strength again in austral summer. The tug-of-war between two macroclimatic systems (WWD vs SHPB) leads to a seasonal climate pattern characterised by wet winters and dry summers. This is the climate of the (southern) ethesial zone, home to the MTE ecosystems of the zonobiome S1. Tropical monsoons are less critical as creators or modifiers of climatic patterns in the Southern Hemisphere. A unique system of this kind is the Indo-Australian monsoon which shapes the climate of northern Australia and close island groups to the north of the Australian continent. Temperate monsoons also occur, although they usually carry other terminological labels. They are onshore eastern flows, such as found offshore of East Australia and eastern shores of South America. Due to their analogy to North America's and Eastern China's climatic systems, the

1.2 Southern Hemisphere in Focus

forest formations on the East Coast of Australia are classified as zonobiome T3. Sea currents, oceans, and seas profoundly impact the climate of the adjacent landmasses. The sea currents are a significant contributor to the re-distribution of warmth (energy), their constellation (changing with the changing tectonics of the continents) is of crucial importance in the shaping of the regional climates under their influence (Winton 2003; Herweijer et al. 2005). In the Southern Hemisphere, the sea currents form three major gyre systems (South Atlantic Gyre, Indian Ocean Gyre, and South Pacific Gyre), circulating counterclockwise. Among the most influential sea currents of the Southern Hemisphere (Pearce 1991), the following ones deserve special mentioning: (1) Humboldt Current (and associated upwelling systems) and Benguela Upwelling that carry cold waters from the Southern Ocean along the coasts of South America and Africa, respectively, in northwards direction. They are the cause of low precipitation underpinning the occurrence of deserts at low elevations along the western seaboards of these continents. (2) The warm currents, including the Brazil Current, East Mozambique and Agulhas Current, Leeuwin Current, and East Australian Current, on the other hand, carry warm tropical waters into high latitudes and climatically ameliorate the east coasts of South America, Africa, and Australia, and underpin the occurrence of warm-loving biomes at relatively high latitudes. The cold, west-trending Antarctic Circumpolar Current is a powerful feature of the global oceanic circulation patterns (e.g. Rintoul et al. 2001; Barker et al. 2007). Besides its pivotal role in the re-distribution of nutrients, it also prevents the penetration of warm waters to the coasts of Antarctica. Due to the isolating cold Antarctic Circumpolar Current and the Circumpolar Trough, the added influence of the prolonged austral winter and the high-elevation central plateau, continental Antarctica is the coldest place on the planet—home to zonobiome A4 (antarctic zone). Finally, elevation is another important proxy driver of zonal climatic (and biotic) patterns. Temperature decreases towards high elevation,

13

and, depending on the position of the mountain range, the alpine regions maybe become bioclimatically detached entirely from the climate of the zone the mountain range is located within. Here temperature dynamics are becoming diurnal rather than seasonal. In Subtropics, these alpine regions are also dry (zonobiome A2: subtropical alpine zone), while in the equatorial Tropics, they are wet (zonobiome A3: tropical alpine zone).

1.2.2 North Versus South: A Brief Story of Two Worlds The Equator splits our planetary ellipsoid into two hemispheres—the Northern and the Southern, presumably of equal size in surface and volume. If these half-ellipsoids are equal, what is so special about the Southern Hemisphere? While the Northern Hemisphere is the hemisphere of land (70% of all land on the planet), the Southern Hemisphere is dominated by oceans and seas. As observed by Chown et al. (2004), between latitudes 30° and 60° North, the ratio of the sea to land is about 1:1. On the other hand, between the same latitudes South, this ratio is approximately 16:1. The fact is that both hemispheres experienced different tectonic dynamics resulting in different constellations of continents shaping disparate ratios between land and sea. The different land constellations and differences in sea dynamics (position of sea currents and upwellings, ocean salinity), in turn, profoundly impact the climates of both hemispheres. Cosmogenic forcing of eccentricity, obliquity, and precession underpin the patterns of solar irradiation reaching the surface of the Earth (Milanković 1930) and hence determine the thermal zones on our planet. Undoubtedly, the sea-toland ratio modifies the effect of the forcing considerably and results in climatic asymmetry between the hemispheres. Because the maritime influence buffers the temperature extremes, the Northern Hemisphere is dominated by continentality, and the Southern Hemisphere should be considered ‘warmer’. Perhaps surprisingly, this is not the case. In 1870 Croll hypothesised that the reverse is the case, and indeed, the data

14

on the heat distribution, especially the northward cross-equatorial ocean heat transport (e.g. Feulner et al. 2013; Kang et al. 2015), makes the Northern Hemisphere warmer. Northern Hemisphere and Southern Hemisphere are homes to three traditional (Aristotelian) climatic zones: torrid, temperate, and frigid. The torrid (tropical) zone is more-or-less similar as they share, although not on equal spatial terms, similar global biomes on both hemispheres. However, the frigid zones are fundamentally different: the Arctic is oceanic, while the Antarctic is continental. The case of the temperate zones is the reverse. While the northern temperate zone is prevalently continental, the southern temperate zone is strongly influenced by vast oceans. These differences make the climatic and biogeographic comparisons between both hemispheres very relevant. Climatic asymmetry between the Northern and Southern Hemispheres is well recognised and understood (e.g. Flöhn 1981; Bonan 2002; Chiang and Friedman 2012; Lee et al. 2017; Roychowdhury and DeConto 2019). Still, this knowledge has not translated well into a system of biomes. A climatic symmetry must translate into similar bioclimatic spaces; hence, this would underpin the potential for the formation of climatically identical (highly similar) biotic zonation on both hemispheres. Unfortunately, this perfect symmetry does not materialise due to the impact of other factors which would modify the unrealistically ideal re-distribution temperature and precipitation on our planet. The lack of recognition of the hemispheric climatic asymmetry in an otherwise very useful system of zonobiomes (Walter 1976a, b) is one of the primary reasons why a new, more critical look at the biomes of the Southern Hemisphere is needed.

1.2.3 A New Look at Biomes of the Southern Hemisphere The biomes of the Southern Hemisphere are featured in several global biome classifications.

1

Biomes of the Southern Hemisphere …

These include the zonobiome account by Walter and Box (1976; for the latest revision, see Breckle and Rafiqpoor 2019), the ‘biome’ scheme by Olson et al. (2001; updated by Dinerstein et al. 2017), and the modelled BIOME4 map (Kaplan 2001; Kaplan et al. 2003). The latter is a non-hierarchical scheme featuring 40 units (incl. 38 biomes). Olson’s ‘biomes’ are defined by lumping bioregions without clarifying the underlying criteria. Hence these ‘biomes’ can hardly be considered functional ecological units. Walter's (1976a, 1976b) zonobiome maps use a nine-member zonobiome scheme; it also uses zonoecotone to denote transitional biome units straddling two zonobiomes. This zonobiome/ zonoecotone scheme, claiming a global scope, had served as the basis of the scrutiny of the biomes of the Southern Hemisphere in this book. However, due to considerable expansion of the zonobiome system, the original coding (and naming) of zonobiomes as suggested by Walter (1976b; see also Walter and Box 1976) and later followed by Breckle (2002), Pfadenhauer and Klötzli (2014, 2020), Breckle and Rafiqpoor (2019) and Körner (2021), had to be reconsidered. None of the three global schemes mentioned above reflects the complexity of the biomes of the Southern Hemisphere. All these schemes are also non-hierarchical, although Walter (1964) and Breckle (2002) introduced a category of subzonobiome, perhaps most consistently followed through only recently by Breckle and Rafiqpoor (2019). Still, I shall follow these two basic principles approaching the biomes of the Southern Hemisphere: (1) I accept the tenets of the Walterian paradigm of zonality and azonality (and hence the associated ecological drivers of those) and recognise this paradigm as the underpinning principle of primary subdivision of biomes. (2) I shall use Walter's global zonobiome system (involving nine zonobiomes) as the starting point for discussing the validity of this system for the Southern Hemisphere. Further as shall apply the biome concept as a large-scale community-ecology unit as defined by Mucina (2019) and the hierarchy of biomes defined by Mucina et al. (2022a, b).

1.3 Why This Book?

15

Here I shall address the success (and failures) This book focuses on the Southern Hemisphere, which might be best defined as the half of of the Schimper-Walterian conceptual framework our planet south of the Equator. For this treatise, in describing and explaining the terrestrial biome however, I shall include the entire of South patterns in the Southern Hemisphere. In more America (90% of which is in the Southern detail, this review is focused upon. Hemisphere), Africa south of the Equator (about 1/3 of the total area of this second largest con- (1) identification of significant inconsistencies and discrepancies in the application of Waltinent), Madagascar, Australia, New Zealand, ter's zonobiome system in the Southern New Guinea, Antarctica and all islands of the Hemisphere; South Atlantic, Indian, Southern and Pacific (2) revision of Walter's system aimed at creating Oceans located south of the Equator. a new global biome system reflecting the I shall focus on significant characteristics of ecological drivers and biogeographic assemthe broadly accepted biomes (e.g. tropical rainbly processes at the zonobiome level; and forest, savanna, tropical dry forest, deserts and semideserts, mediterranean-type ecosystems) to (3) characterising the zonobiomes (and their constituents at the global and continental provide some background to the discussion of biome levels of hierarchy) of the Southern identified problematic biomes. These are those Hemisphere in ecological and biogeographiwhere previous researchers frequently disagree cal terms by resolving the most pressing on their position in relation to the broadly problematic issues. accepted biomes.

1.3

Why This Book?

The concept of biome is experiencing a comeback of sorts (Mucina 2019). A Google Scholar search for ‘biome’ (accompanied by the term ‘ecology’) for 2000–2020 has yielded 43.700 bibliographic items. Adding two more years (2021–2022) added another 1300 items. Interestingly, the search period spanning 1980 and 1999 yielded only 12.200 items. Clearly, as in the past also today, this concept/term has been used in many connotations—adding to the conflation of both its original (Clements) as well as modified, spatially explicit (Shelford) meaning. It is not an ambition of this review to discuss all problems the term biome might be confronted with. Instead, I shall focus on one of the most influential conceptual frameworks of biome ecology—that of Heinrich Walter. Walter has considered Andreas Schimper a mentor, and undoubtedly many elements of his conceptual framework build on Schimper’s scientific contribution. Perhaps it would be fair to call this approach ‘SchimperWalterian’.

The most prominent problems I will address include the following: (1) distinction between subtropical and tropical forests, (2) origins of the multiple-faceted savanna formations, (3) origins of the ‘underground forests’, (4) odd existence of tropical dry forests, (5) the complexity of hot semideserts and deserts, (6) status of the biome classification of subtropical and tropical thickets, (7) the complexity of temperate forests in the Southern Hemisphere and their global position, (8) controversial biome identity of tropical montane cloud forests, (9) rediscovery of the antiboreal zone, (10) the notorious ‘Pampa-Problem’, (11) natural status and the biome position of the grasslands of the Southern Hemisphere, (12) the usefulness of Walter's orobiome concept, and (13) the origins and biome position of the southern alpine biomes.

16

1.4

1

Procedures and Tools to Address the Goals

To achieve the goals set above, I shall

Biomes of the Southern Hemisphere …

(vegetation type) units and spatially explicit climatic stations within the spatially defined vegetation unit. Using intra- and extrapolations and averaging procedures, a spatial climatic diagram is then constructed using GIS tools. The climate diagrams (CDs) used in this paper come from various sources, namely:

(1) review vegetation-ecological and biogeographical literature of biome-scale relevance (large-scale biome and vegetation mapping (1) Some CDs were sourced from Mucina and studies); Rutherford (2006); for the construction of (2) interpret those large-scale ecosystem patthese CDs, and the explanation of the cliterns in terms of the Walter’s zonobiome matic data accompanying the CD, see approach, involving additional data sources, Mucina et al. (2006a). especially bioclimatological, geological, (2) Unpublished CDs of the units of the Andean pedological, and hydrological; ecosystem units (Josse et al. 2009a, b) were (3) explore the available climatic data banks to constructed by L. Mucina and L.W. Powrie create bioclimatic envelopes (spatial cliusing the same methodology as presented in matic diagrams) to identify and explain Mucina et al. (2006a). potential discrepancies between the Schimper-Walterian conceptual framework (3) Finally, most CDs are based on the spatial extent of selected WWF ecoregions (Dinerand Southern Hemisphere ecosystems; and stein et al. 2017). The codes and the naming (4) revise the Schimper-Walterian conceptual of the unit follow the original WWF sources framework or introduce an alternative —also in cases where the names appear model that would more robustly underpin radically inappropriate or misleading. The the biome systems on both Hemispheres. only correction introduced in the original WWF unit names was the capitalisation of all 1.5 Climate Diagrams as Bioclimatic words constituting the name of units for Fingerprints grammatical correctness (the names of the units are unique, not generic, labels). (co-authored by James L. Tsakalos and Ladislav The appearance of a climate diagram is capMucina) Ever since the seminal works of Louis tured in Fig. 1.4. We constructed the climatic profiles of the Emberger (1930, 1955) and Heinrich Walter (Walter 1955; Walter and Lieth 1967; Walter biomes using WorldClim and Mapzen’s digital et al. 1975), climate diagrams (also known as elevation product. We sourced the mean monthly ‘climographs’) have become an effective tool of precipitation and temperature and maximum and bioclimatology and ecology. The original Wal- minimum monthly temperature data of Worldterian climate diagram, focusing on yearly Clim version 2 (Fick and Hijmans 2017) at a 30 dynamics (stratified by months) of temperature arc-second scale (*1 km, 0.00833°). We accesand precipitation (rainfall), has undergone some sed and downloaded the WorldClim data using modifications (e.g. Breckle and Rafiqpoor 2019). the ‘WorldClim Version2’ internet portal. Sourcing elevation data presented a unique Invariably, all those climate diagrams featured a long-term climate of a particular spot. Perhaps challenge; the most commonly used digital elethe most important qualitative innovation in this vation model source, NASA Earth Explorer's respect was developed by M.C. Rutherford non-void-filled satellite radar topographic mis(Mucina et al. 2006a). These authors introduce a sion series (Farr et al. 2007), does not cover areas new type of climatic diagram. Their spatial cli- of Europe north of 60°. Mapzen’s product is matic diagram uses well-defined ecological unique in that it combines several sources of

1.5 Climate Diagrams as Bioclimatic Fingerprints

17

Fig. 1.4 The graphical explanation of the variables involved in constructing a climate diagram

digital elevation models, including SRTM, the ArcticDEM (covering all areas north of 60°; Morin et al. 2016), EUDEM (digital elevation model over Europe; for review, see Mouratidis and Ampatzidis 2019), and others into a single product (= terrain tiles). We accessed the terrain tiles freely through Amazon Web Services using the ‘get_elev_raster’ function from R’s elevatr package (Hollister 2021). We supplied the Biome map, imported into R using the ‘st_read’ function from R’s sf package (Pebesma 2018), as the ‘locations’ argument in the ‘get_elev_raster’ function. Also, within the ‘get_elev_raster’ function, we specified the ‘zoom’ (i.e., resolution of the resultant raster) argument as 7, corresponding to 611.5 m ground resolution at 60° latitude, 864.8 m at 45° and 1223 m at 0°. The new terrain tiles dataset, matching the extent of the Biome map, was then exported as a tiff using the ‘writeraster’ function from the raster R package (Hijmans 2021). We obtained mean, minimum, and maximum values for each variable for all of the WorldClim and the terrain tiles data using the ‘zonal statistics as table’ tool within ArcGIS v10.3 for the area of each zonal biome. We decided to import all data into ArcGIS because we could easily

visualise the raster and biome spatial distributions (serving as a quality checkpoint). In addition, it has accelerated processing speeds (compared to R alternatives). We then imported the extracted variables (as comma-separated files) into R (R Core Team 2021). Once imported, the variables were passed to the biovars function in the ‘dismo’ R package (Hijmans et al. 2021), where we calculated all 19 bioclimatic variables. Some of these derived variables (indicated below) feature in the climate diagrams. In addition to these bioclimatic variables, we used base R coding to calculate Holdridge’s (1966) biotemperature and potential evapotranspiration (BioT and PET, resp.), the number of dry months (Dry mo), and precipitation seasonality (PS). The core of a climate diagram features temperature and precipitation patterns. The red lines in a diagram indicate the patterns of the Mean Monthly Minimum and Mean Monthly Maximum temperatures. The Mean Monthly Precipitation is depicted by the blue bars. All data are sourced from WorldClim version 2 (Fick and Hijmans 2017) and represent the variables tmin_1 to tmin_12, tmax_1 to tmax_12, prec_1 to prec_12.

18

BioT (Biotemperature): It is the temperature range in which the effective growth of plants occurs. We calculated the biotemperature as the sum of all monthly temperatures greater than 0 ° C and less than 30 °C divided by 12. The values are small towards the poles, where the mean annual temperatures are low, whereas BioT is large in the Tropics with the highest mean annual temperatures. Across the biomes of the Southern Hemisphere, BioT ranges from 6.9 to 11.7. For perspective, the Nival region (at latitudes spanning 9°–67°22.5′ N or S) have BioTs close to zero, and the Tropics (i.e. 13°–0° N or S) have values greater than 24 (see Holdridge 1966). ISO (Isothermality) quantifies how large the day-to-night temperatures oscillate relative to the summer-to-winter oscillations, given in per cent. The variable presented in the climate diagrams represents ‘BIO3’ calculated using R’s ‘dismo’ package. An ISO value of 100 indicates a minor temperature variability within an average month relative to the year. The average ISO value calculated within the Southern Hemisphere biomes ranges from 13.9 to 92.7, compared to the global range of 7 to 96. MAT (Mean Annual Temperature): The mean temperature in °C uses the average monthly temperature averaged over twelve months. The variable presented in the climate diagrams represents ‘BIO1’ calculated using R’s ‘dismo’ package. The average value of MAT calculated within the biomes of the Southern Hemisphere ranges from ‒17.4 to 30.2 °C compared to the global range of ‒29.0 to 32.0 °C. TS (Temperature Seasonality): This is the amount of temperature variation over a given year (or averaged years) based on the standard deviation (variation) of monthly temperature averages. The variable presented in the climate diagrams represents ‘BIO4 ‘ calculated using R’s ‘dismo’ package. The average value of TS calculated within the biomes of the Southern Hemisphere ranges from 9.1 to 1895.2 compared to the global range of 62–22,721. Dry Months (Dry mo): We defined the number of ‘dry months’ as the number of months in the

1

Biomes of the Southern Hemisphere …

year (between 0 and 12) for each biome with less than 50 mm of rainfall during the month. MAP (Mean Annual Precipitation) is given in mm. The variable presented in the climate diagrams represents ‘BIO12’ calculated using R’s ‘dismo’ package. The average value of MAP calculated within the biomes of the Southern Hemisphere ranges from 16.2 to 4578.7 compared to the global range of 0 to 11,401. PET (Potential evapotranspiration ratio) is the quantity of water given to the atmosphere within a zonal climate and upon a zonal soil by the area's natural vegetation. If sufficient but not excessive, water were available throughout the growing season. The PET variable, taken from Holdridge (1966), was calculated as the BioT/MAT  58.93. The average PET value calculated in the Southern Hemisphere biomes ranges from ‒2.6 to 22.9. When the ratio is