Plant Ecology in the Middle east

Plant Ecology in the Middle East

Plant Ecology

in the Middle East

Ahmad Hegazy

University of Cairo, Giza, Egypt

Jonathan Lovett-Doust

University of Windsor, Windsor, Ontario, Canada

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1

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We dedicate this book to our students, and are deeply grateful to our spouses for all of

their help and support during its preparation.

We also dedicate this book as a message to all the people and countries of the region:

may we all work together to build peace and conservation, stability and prosperity for

the region.

vii

The Middle East has a rich natural history; however

study of the diverse flora of the region has been in￾termittent, and usually localized. Human activities

over time have both enriched and damaged biodi￾versity. Early on, medicinal plants and crops in the

region were domesticated; on the other hand, envi￾ronmental pollution, rampant coastal development,

and overgrazing have all negatively impacted

ecological functioning, while warfare and dis￾puted borders have delayed systematic study, and

to many outsiders the Middle East seems exotic,

even mysterious. We believe a better understand￾ing of the plant ecology of the region will allow us

to understand and anticipate the effects of climate

change in arid and semi-arid regions worldwide,

and for that reason as well as the inherent fascina￾tion the region holds as a “cradle of civilization,”

a book on the current state of knowledge seems

timely. Our goal is to provide a solid baseline and

stimulate further research.

We have taken a “plant’s-eye perspective” on the

Middle East and include all the biogeographic re￾gions contributing species. For us, the Middle East

includes parts of Africa, Europe, Asia, and Arabia,

covering some 13.5 million km2. We integrate plant

geography, and evolutionary and population ecol￾ogy with information on the life histories of species

found in the deserts, mountains, and coastal re￾gions of the Middle East. We hope this integrative,

empirical approach to the region’s plant ecology, set

in a context of plant evolution and adaptation to un￾predictable resources, may be of interest to dryland

specialists, ecologists, conservation biologists, and

climate change researchers everywhere.

Chapter 1 introduces the several major elements

of the book’s scope that will help us understand the

present day distribution and abundance of plants

across the Middle East. We overview previous stud￾ies of the flora then outline the general nature of

deserts and importance of water in these dryland

environments. We explore effects of long-term cli￾mate change and the formation of “climate relicts,”

(the plants of the Middle East have experienced cli￾mate change in the past, too) and effects of heteroge￾neity in time and space on a species’ “regeneration

niche” (the particular environment that is necessary

for successful seed germination and juvenile sur￾vivorship). In the Middle East various iconic tree

species exist as stands of aging individuals that are

simply not being replaced through natural regenera￾tion. The region includes many precious and unique

sites, for example vestigial “valley-forest” in Arabia,

many of which have been reduced to a few highly

degraded remnant populations in the southwest

(exemplifying the urgency of regional conservation

strategies to protect the flora of the Middle East).

Chapter 2 offers a tour of the region, outlining the

plant ecology of some 24–25 countries, including

parts of Africa and Eurasia as well as the Arabian Pen￾insula, with many mountain ranges, plains, plateaux,

and some islands—not least the botanically fabulous

Socotra. The tour is intended to give some overall

sense of the entire region—a vast place with many

different kinds of habitat. Some, like the montane

cloud forests of Oman, Yemen, and Egypt, for exam￾ple, are biodiverse and spectacular. Others are more

homogeneous—often with few species because con￾ditions are more extreme. . . these sites are typically

hotter, flatter, and drier, as in for example, the sparse

communities of the “Empty Quarter” of Saudi Arabia.

Chapter 3 shows how the Middle East and its

plants came together as a product of geologi￾cal “deep time,” starting with major geological

events at least some 23 million years ago. The plant

Preface

viii Preface

colleagues and students with whom we have been

fortunate to work over the years; they have helped

shape our thinking on the elements of plant ecol￾ogy. This includes Drs. H. Adawy, M. Cadotte, A.

El-Keblawy, N. Gomaa, M. Imam, A.-H. Khedr, H.

Murphy, M. K. Okla, O. Sharashy, E. Badawi, and

J. Vanderwal. We appreciate all the kind help given

by Drs. Hanan Kabiel and Sanad Al-Sobeai at vari￾ous stages of the book’s preparation.

We are particularly grateful to Dr. Abdel Aziz

Assaeed, Dr. Saud Al-Rowaily, and Dr. Magdy El￾Bana who showed us so many interesting habitats

and locations during field trips in Saudi Arabia, and

shared photos and source materials. Special thanks

go to friends among the local residents there: Mr.

Naser Al Shedwy, his son Osama Al Shedwy, and Dr.

Riyad Basahi who all provided valuable logistic sup￾port and acted as field guides and instructors during

field trips in the western and southern mountains

of Saudi Arabia. Without their help many otherwise

inaccessible places in that wonderful mountainous

landscape could not have been reached.

We are grateful to our taxonomic colleagues, es￾pecially Drs. Fahd Al Hemaid, Ibrahim El-Garf, Ja￾cob Thomas, and Wafaa Amer for help in species

identification and nomenclature, and for sharing

source materials.

We are very grateful to the following individu￾als who generously gave their time to review some

or all of the book in early stages: Peter Sale, who

plowed through the entirety of an early draft and

provided many useful insights and helpful sugges￾tions; Marc Cadotte, Ali El-Keblawy, and Carl Free￾man who all read early material and prompted us

toward helpful improvement. Lesley Lovett-Doust

very kindly read nearly everything, sometimes

more than once, and made many important sugges￾tions at all stages of the book’s production.

We thank everyone who has granted us permission

to include previously published materials. We are

particularly grateful to Drs. Avi Shmida and Bruno

Mies for their kind encouragement and permission

to use selected material from their published work

on Middle Eastern phytogeography and ecology.

Leo Lovett-Doust helped greatly with the prepa￾ration of figures and tables and with the book’s

digital coordination. Dr. Mohamed El Hag kindly

helped with drawing the maps.

populations and communities we have today rep￾resent remnants of their past. We explore in some

detail examples of ancient forest relicts—the spec￾tacular Dracaena forests of Socotra, various oak￾laurel forests, the refreshing juniper forests of the

coastal areas, and the Djibouti Bankoualé Palm.

Chapters 4 and 5 explore the constraints of liv￾ing in desert and dryland ecosystems, in particu￾lar dealing with unpredictable water supplies and

spatial heterogeneity. These in turn generate habitat

diversity and specialized plant forms, developing

succulence, water-conserving photosynthesis and

other adaptations to deal with excessive drought

and salt in the environment. Given the significance

of mountains throughout the region we discuss

effects of elevation and isolation on plants and re￾gional patterns of species richness and endemism.

Chapters 6–8 focus on plant reproduction in the

dryland world. To succeed in this unpredictable en￾vironment plants need to be able to sense the envi￾ronment and respond to opportunities with speed;

it is easy to see how such life history strategies can

be seen as evidence of plant “intelligence”—these

organisms are integrating different stimuli and pro￾tecting their descendants through strategic seed

dispersal and dormancy. In such environments

plants often have complex “secondary chemistry,”

producing many anti-herbivore compounds and

others that inhibit competitors. Chapter 9 explores

the domestication of plants in the region and the

many reciprocal effects of agriculture and its early

development on plant ecology there.

Chapter 10 outlines the major challenges to plant

conservation in the region and proposes strategies

for successful conservation, starting with the major

Middle Eastern “biodiversity hotspots.” A final chap￾ter draws together some general conclusions about

the plant ecology of the region. As a general note

on spelling and transliteration from the Arabic: is a

mountain range here to be gebel, jabal, or djebel, etc.?

Is the thirsty, stimulating plant Catha edulis to be de￾scribed as khat or qat, etc.? For the most part we have

simply adopted the style used by our sources; we gen￾erally do not hyphenate the definite article, but again

follow precedent, thus Al Ain and El-Keblawy. . .

We are grateful to many people who have kindly

helped us in various ways to produce this book.

Perhaps first and foremost we thank the many

ix

1 “Drylandia” and the dawn of time: Introduction to plant ecology

in the Middle East 1

1.1 Introduction 1

1.2 Which Middle East? 3

1.3 Previous plant studies of the Middle East 5

1.4 Hot, dry, hot and dry? 7

1.4.1 Cloud forests 9

1.4.2 Plants of the Rub’ al-Khali 10

1.4.3 Climate change, salt, and endorheic basins 12

1.5 Crustal, tectonic effects 14

1.5.1 The Red Sea 15

1.5.2 Ongoing activity 15

1.5.3 The Gulf 16

1.6 The more recent past 17

1.7 Climate relicts and the “regeneration niche” 18

1.7.1 Facilitative interactions (and “plants helping plants”) 19

1.8 Water as a trophic currency 19

1.9 Endemism and species range 21

1.10 Primal forest in Arabia and conservation 23

1.11 Summary 25

2 The lay of the land: Plant geography in the Middle East 27

2.1 Boundaries 27

2.2 Geological characteristics 27

2.3 Coastal and desert environments 28

2.4 Mountains and plateaux of the Middle East 30

2.5 Rivers 31

2.6 Libya 31

2.7 Egypt 33

2.8 Sudan: the Red Sea Hills and Jebel Marra ranges 35

2.8.1 Sudd swamps 37

2.9 Ethiopia and the Horn of Africa 40

2.10 The Red Sea and Gulf of Aden Basins 41

2.11 Yemen (and Socotra) 42

2.11.1 Endemism in Yemen 45

2.11.2 Socotra 45

2.11.3 The Socotran flora 46

Contents

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x Contents

2.12 Oman 48

2.13 United Arab Emirates 50

2.13.1 Plants of the UAE 51

2.13.2 The eastern UAE and Musandam Peninsula 52

2.14 Saudi Arabia 54

2.14.1 Plant resources and endemism in the Saudi flora 57

2.15 Bahrain 58

2.16 The Hawar Islands 58

2.17 Qatar 59

2.18 Iraq 60

2.19 Kuwait 62

2.20 Jordan 63

2.21 Israel, West Bank, and Gaza 65

2.21.1 Vegetation of the mesic parts of Israel and Jordan: Maquis

and forest 66

2.21.2 Open forests of Quercus ithaburensis, and other vegetation 66

2.22 Syria 67

2.23 Lebanon 68

2.24 Cyprus 69

2.25 Turkey 70

2.26 Iran 72

2.27 Armenia 76

2.28 Azerbaijan 77

2.29 The mountainous Caucasus 77

2.30 Summary 78

3 Continents in motion and global climate change: Understanding past

and present plant communities 79

3.1 Miocene tectonics (23–5.3 Ma) and present-day plant communities:

Ghosts of floras past 79

3.2 Relictual vegetation 82

3.3 Socotran Dragon’s-blood trees and other relicts of Mio-Pliocene

Laurasian subtropical forests and climate change 84

3.4 Djibouti and aging populations of the Bankoualé Palm, Livistona carinensis 86

3.5 Genetic “footprints” of past vegetation change, and current

populations of oaks and laurels 88

3.6 Relictual junipers in the Middle East 90

3.7 Deserts in the Middle East 91

3.8 Desertification and climate warming 92

3.8.1 Drivers of desertification 94

3.9 Summary 95

4 The desert as a heterogeneous environment 97

4.1 Introduction: Deserts and desert vegetation types 97

4.1.1 Trees and shrubs in the global desert flora 100

4.1.2 Low shrubs and chamaephytes 100

4.2 Desert phytogeography 100

Contents xi

4.3 Desert growth forms and Cactaceae 104

4.4 Desert plant communities 105

4.5 Desert ecosystems and specialized habitats 108

4.5.1 Nabkhas 110

4.5.2 Sabkhas 114

4.5.3 Wadi ecosystems 115

4.6 Coasts and mangroves 116

4.7 Facilitation effects and the regeneration niche 119

4.8 Comparing desert and Mediterranean ecosystems 122

4.9 Elevation and warming 126

4.9.1 Patterns of species richness, elevation and the

“mid-domain effect” 126

4.10 Regional ecology: Plant metapopulations vs. landscapes 127

4.11 Connectivity and the background matrix from a plant perspective 129

4.12 Summary 130

5 On growing up dry 131

5.1 Introduction to dryland plant adaptations 131

5.2 Succulence 133

5.2.1 Succulence and altitudinal differentiation in Yemen’s

Haraz Mountains 137

5.3 Succulence and sclerophylly, foliage angles, and other strategies

for dealing with drought 137

5.4 Degrees of leaf, stem, and caudex succulence 139

5.4.1 Drought survival strategies 140

5.5 Dryland photosynthetic variability 142

5.6 Spinescence (and keeping the grazers at bay) 143

5.7 Euphorbia and the Middle Eastern cactus niche 145

5.8 Halophytes and living with salt as a compounding variable 148

5.9 Desert life forms, demography, and dynamics 153

5.9.1 Life history variation and life-tables 157

5.10 Summary 160

6 Sex in a hot dry place 163

6.1 The importance of timing! 163

6.2 Pollination syndromes in the desert 165

6.3 Breeding systems 166

6.4 Semalparous flowering 166

6.5 Apomixis (asexuality and a balance between long￾and short-term advantage) 167

6.6 Sexual specialization and lability in expression 168

6.6.1 Thymelaea hirsuta 169

6.6.2 Atriplex canescens 169

6.6.3 Ochradenus baccatus 170

6.6.4 Acer negundo 171

6.6.5 Pinus halepensis 171

6.6.6 Diplotaxis harra 173

xii Contents

6.7 Euphorbia species 174

6.8 Acacia, a keystone tree species in the Middle East 177

6.9 Summary 178

7 Seed dispersal, dormancy, and “bet-hedging” in desert plants 179

7.1 Introduction 179

7.2 Dispersal in the desert 180

7.3 Variable germination in the desert 183

7.4 Serotiny 187

7.5 Dormancy 187

7.6 Annual species 188

7.7 Fleshy-fruited perennial species 192

7.8 Non-fleshy-fruited perennials 193

7.8.1 Acacia species—herbivory—bruchid beetle and other biotic

interactions 193

7.8.2 Other species 195

7.9 Vicariance (and scattered vestiges of Gondwanaland in Socotra) 198

7.10 Summary 201

8 Chemical ecology in the desert 203

8.1 “Intelligent” plant behavior 203

8.2 Allelopathic interactions 204

8.3 Interactions between annuals and perennials 205

8.4 Life history strategies 207

8.5 Effects on seed germination and seedling growth 208

8.6 Some case studies 208

8.6.1 Anastatica hierochuntica 208

8.6.2 Chenopodium species 210

8.6.3 Prosopis juliflora 212

8.6.4 Coffea arabica 213

8.6.5 Artemisia species 213

8.6.6 Host–parasite allelopathy 213

8.6.7 Other species 214

8.7 Summary 214

9 Agriculture and plant ecology 215

9.1 Gardening, win–win, and the evolution of cultures 215

9.2 The plant’s-eye-view 217

9.3 Early agricultural societies 218

9.4 Omani oasis agriculture 220

9.5 Domestication and selection 222

9.6 Humans, horses, and camels 225

9.7 Fruit trees and early fruit cultures 227

9.8 Plant resins 229

9.9 Eco-crises and water shortages 229

9.10 Summary 233

Contents xiii

10 Human impacts and plant conservation 235

10.1 Introduction 235

10.2 Deforestation and wood collection 238

10.3 Overgrazing 239

10.3.1 Camel grazing 241

10.4 Effects of grazing on Omani juniper forest decline 242

10.5 Collection of plant materials 243

10.6 Land conversion and shifting agriculture 244

10.7 Damming of rivers and wadis 245

10.8 Water recharge wells 247

10.9 Sediment removal 249

10.10 Mining, quarrying, and petroleum-related activities 249

10.11 Road construction 249

10.12 Warfare 250

10.13 Invasive species 251

10.14 Coastal development and recreation 253

10.15 Biodiversity hotspots 254

10.16 In situ and ex situ conservation 257

10.17 Populations and the “abundant-center” model 260

10.18 Rear-edge populations and opportunities for conservation 262

10.19 Summary 263

11 Conclusions 265

11.1 Introduction 265

11.2 Desert “stress” and the plants that live there 266

11.3 Biodiversity hotspots 268

11.4 Desert selections: cooperation and “plants helping plants”, dispersal

and “bet-hedging” strategies, and absent tree regeneration 270

11.5 Global climate change and possible shifts in vegetation 273

11.6 “Keystone” species as a source of stability and ecological resistance 275

11.7 Overgrazing and the acceleration of desertification 276

11.8 Priorities and areas for further research 276

11.9 Ongoing challenges 277

11.10 Summary 278

Appendix 1: What’s in a (plant) name? 281

1 Many names reflect their most prominent feature 281

2 Location. Location. Location. Plants are often named based on where they

live—or where they came from 282

3 And then there are the people . . . 283

Appendix 2: Species list 285

References 301

Index 335