Soils as a Key Component of the Critical Zone 1 E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 569

Veröffentlichungsjahr: 2018

Beschreibung

This introductory book to the six volume series includes an introduction defining the critical zone for mankind that extends from tree canopy and the lower atmosphere to water table and unweathered rock. Soils play a crucial role through the functions and the services that they provide to mankind. The spatial and temporal variability of soils is represented by information systems whose importance, recent evolutions and increasingly performing applications in France and in the world must be underlined. The soil functions, discussed in this book, focus on the regulation of the water cycle, biophysicochemical cycles and the habitat role of biodiversity. The main services presented are those related to the provision of agricultural, fodder and forest products, energy, as well as materials and the role of soil as infrastructure support. They also include the different cultural dimensions of soils, their representations being often linked to myths and rites, as well as their values of environmental and archaeological records. Finally, the issue is raised of an off-ground world.

Leseprobe

Table of Contents

Cover

Foreword

1 Soils as a Key Component of the Critical Zone

1.1. What are soils?

1.2. The Earth, land, soils, soil cover and the Critical Zone

1.3. The term “soil” has various meanings according to use and function processes

1.4. The concept of soil varies according to the user

1.5. The approaches and procedures of soil scientists and pedologists

1.6. Two principles to take into account: geographical continuity and multi-temporality

1.7. Nature, organization and major modes of soil processes

1.8. The functions and services of soils

1.9. The need and significance of soil information systems

1.10. Conclusion and recommendation

1.11. Bibliography

2 Understanding Soils for Their More Efficient Management: A National Soil Information System

2.1. Introduction

2.2. The inventory and monitoring of soils in Europe and in the world

2.3. National mechanisms for the acquisition of soil data

2.4. Data exploitation for the production of maps and indicators

2.5. Dissemination and availability of data

2.6. Conclusion

2.7. Bibliography

3 Soils and Regulation of the Hydrological Cycle

3.1. The soil – facilitator within the hydrological cycle

3.2. Soil control mechanisms

3.3. Impacts on the hydrological cycle at soil cover scale

3.4. Conclusions

3.5. Bibliography

4 Soils as Bio-physicochemical Reactors

4.1. What is a reactor?

4.2. Soil components

4.3. Reactivity drivers

4.4. Main reactions within soils

4.5. Biogeochemical evolution of the Earth’s surface and the consequences for soils

4.6. Soil, biogeochemical reactor of soil formation

4.7. Soil structure: a case of “soft matter”

4.8. Bibliography

5 Soils are Biosystems, Habitats and Reserves of Biodiversity

5.1. Introduction

5.2. Emergence and development of microbial ecology and soil biology

5.3. Soil microbial communities

5.4. Diversity of energy and nutritional pathways of microorganisms, key players in biogeochemical cycles

5.5. Richness and diversity of soil fauna

5.6. Soils, environments with energy and nutritional conditions favorable to microbial life and fauna

5.7. Determinants and remarkable sites of diversity and soil biological activities

5.8. Tools for understanding the habitats of soil organisms

5.9. Specificities of the soil fauna

5.10. Soil organisms: ecosystem service actors

5.11. Soil quality indicators

5.12. Conclusion and perspectives

5.13. Bibliography

6 Soils, a Factor in Plant Production: Agroecosystems

6.1. Introduction

6.2. Evolution of soil–agriculture relationship over the last few decades

6.3. Agricultural capability of soils

6.4. Agricultural practices that alter soil properties

6.5. Toward sustainable management of agricultural soils

6.6. Conclusion

6.7. Bibliography

7 Forest Soils: Characteristics and Sustainability

7.1. Forest soils

7.2. Bioavailability of nutrients: soil–plant coevolution and the role of the biological cycle

7.3. Concept of forest soil fertility

7.4. Specificity of forest soils compared to agricultural soils

7.5. Threats to forest soils

7.6. Conclusions

7.7. Bibliography

8 Soils and Energy

8.1. Soils at the heart of global issues

8.2. Energy context

8.3. Soils, energy supports and energy suppliers

8.4. The consequences of energy production on mobilization, occupation and land-use change

8.5. Impacts of energy production on soil loss, degradation and quality

8.6. Conclusion

8.7. Bibliography

9 Soils, Materials, and Infrastructure Supports

9.1. The use of “raw” soils as building materials

9.2. Soils, infrastructure supports

9.3. The classical civil engineering versus the physical approach of granular media

9.4. Consumption of agricultural land, forest or natural areas by urban sprawl

9.5. The use of separate particle size fractions

9.6. The use of chemical elements after extraction and treatment

9.7. Bibliography

10 Cultural Dimensions of Soils

10.1. Soil representations: the Earth celebrated

10.2. Humanity, Earth and soil: myths and rites

10.3. Bibliography

11 Environmental and Societal Memories of Soils

11.1. Ancient soils: archives of human history

11.2. Methods of studying soil memory

11.3. Reading the ancient soil memory

11.4. Conclusion and perspectives

11.5. Bibliography

12 A Mesological Point of View

12.1. Soil ubiquity

12.2. Soil as…

12.3. Off-ground?

12.4. Living off-ground

12.5. Limits of the off-ground

12.6. Conclusion

12.7. Bibliography

List of Authors

Index

End User License Agreement

List of Tables

2 Understanding Soils for Their More Efficient Management: A National Soil Information System

Table 2.1. Strategies of various national programs for soil data acquisition

3 Soils and Regulation of the Hydrological Cycle

Table 3.1. Variability of soil water budget components among three soils with different textures over a period of 273 days from April to September. The values are in millimeters

4 Soils as Bio-physicochemical Reactors

Table 4.1. List of elements necessary for the construction of a living cell and supply sources used by the living organism (source: [MAU 99, ELA 16]), redrawn

5 Soils are Biosystems, Habitats and Reserves of Biodiversity

Table 5.1. Average densities and biomasses of the main taxa of soil organisms

6 Soils, a Factor in Plant Production: Agroecosystems

Table 6.1. Criteria defining limiting soils (Annex III of Regulation 1305/2013 of the European Commission of December 2013). In France, disadvantaged areas outside the mountains represent about 30% of the UAA (utilised agricultural area). They have been defined from Référentiels Régionaux Pédologiques (RRP) [regional pedological standards], set up within the framework of the Groupement d’Intérêt Scientique Sol (Gis Sol, Soil Scientific interest Group). There are also criteria for excess water in the soil and low temperatures, but no area, outside mountain areas in mainland France, is affected by these criteria in France. Thus, even within agricultural areas, there are highly variable production potentials, of which soils are an essential component, the map of useful water reserves of soils being an illustration (Figure 6.1)

7 Forest Soils: Characteristics and Sustainability

Table 7.1. The annual average flows of the life cycle in a 70-year-old Douglas fir stand (Pseudotsuga menziesii Franco) in the Beaujolais Mountains (data in kg.ha

−1

.yr

−1

for the plant and in kg.ha

–1

for the soil)

Table 7.2. The efficiency of tree species to produce forest biomass expressed in tonnes of ligneous dry matter produced per kg of element immobilized: the effect of rotation length on efficiency (source: J. Ranger). For a color version of this figure, see www.iste.co.uk/berthelin/soils1.zip

8 Soils and Energy

Table 8.1. Land use intensities, land take and sealing ratios by electricity, heat and biofuel generation technology produced or imported in France (* For wind or PV farms, the total area is defined by the external perimeter of the installations; for bioenergy, the total area is the area mobilized to produce energy crops; for fossil fuels, the total area is essentially that defined by the outer perimeter of the extraction zone/s; † land take: artificial land surface/total surface area of the park ratio; ‡ sealing: sealed surface area/total area of the park ratio)

Table 8.2. Land use intensities by electricity and biofuel production technology, international data (source: a [MCD 09] (recalculated Land use intensity in the case of nuclear energy); b [PIM 02]; c [NRC 96]; d [DEN 08]); e [FTH 09]. * For wind or PV farms, the total area is defined by the external perimeter of the installations; for bioenergy, the total area is the area mobilized to produce energy crops; for fossil fuels, the total area is essentially that defined by the outer perimeter of the extraction zone/s

Guide

Cover

Table of Contents

Begin Reading

Pages

C1

iii

iv

v

xiii

xiv

xv

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

233

234

235

236

237

238

239

240

241

242

243

244

245

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

284

285

286

287

288

289

290

291

292

293

294

295

296

297

298

299

300

301

302

303

304

305

306

307

308

309

310

311

312

313

315

316

317

318

319

320

G1

G2

G3

e1

Soils Set coordinated by Christian Valentin

Series Editor – André Mariotti

Volume 1

Soils as a Key Component of the Critical Zone 1

Functions and Services

Edited by

Jacques Berthelin

Christian Valentin

Jean Charles Munch

First published 2018 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:

ISTE Ltd

27-37 St George’s Road

London SW19 4EU

UK

www.iste.co.uk

John Wiley & Sons, Inc.

111 River Street

Hoboken, NJ 07030

USA

www.wiley.com

© ISTE Ltd 2018

The rights of Jacques Berthelin, Christian Valentin and Jean Charles Munch to be identified as the authors of this work have been asserted by them in accordance with the Copyright, Designs and Patents Act 1988.

Library of Congress Control Number: 2018944663

British Library Cataloguing-in-Publication Data

A CIP record for this book is available from the British Library

ISBN 978-1-78630-215-1

Foreword

ISTE’s scientific publications include a pluridisciplinary editorial sphere entitled “Earth Systems – Environmental Sciences” and, within this domain, we are now pleased to release a series of works entitled Soils, coordinated by Christian Valentin, as part of the activities of the working group on soils at the Académie d’Agriculture de France (French Academy of Agriculture).

The general title of this series of works, “Soils as a Key Component of the Critical Zone” merits a number of comments.

The Critical Zone (CZ), a concept which is now globally recognized, designates the location of interactions between the atmosphere, the hydrosphere, the pedosphere – the outermost layer of the Earth’s crust, made up of soils and subject to the processes for soil formation, derived from interactions with the other surface components – the lithosphere and ecosystems. Within this zone, there are vital exchanges of water, matter and energy, such exchanges interacting with those of other layers, both oceanic and atmospheric, within the Earth system. Its extreme reactivity, whether physical, chemical or biological, is an essential factor of the overall regulation of this Earth system.

Supporting all forms of life, this thin layer has a high level of interaction with human activities. Examples of these are agriculture, urbanization, resource extraction, waste management and economic activities.

This concept of the Critical Zone (CZ) entirely revives the environmental approach, simultaneously enabling an integrated, descriptive, explanatory and predictive view of the Earth system, of its major biogeochemical cycles and their interaction with the climate system. The view becomes dynamic, explaining all interactions, and opens the way for predictive modeling. Such processes are necessarily integrated with given models, paying special attention to the hydrological cycle as well as the carbon and nitrogen cycles.

Within the CZ, soil is a key component, playing a prominent role in the storage, dynamics and conversion of biogenic elements (carbon, nitrogen, phosphorous – C, N, P) and of all inorganic, organic or microbiological contaminants. This contributes to significantly affecting the quantity and the quality of the essential resources for human activity, these being soils, water and air quality.

Soils thus return to the top of the international agenda, as a result of the major challenges for any civilization. These include agricultural production, climate change, changes and conflicts over land use (deforestation, urbanization, land grabbing and others), biodiversity, major cycles (water, carbon (C), nitrogen (N) and phosphorous (P)), pollution, health, waste, the circular economy, and so on. They appear therefore legitimately within the United Nations’ “sustainable development goals” by 2030 (SDG 15: “Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss”).

The study of soils, as a key component of the Critical Zone, should thus not only be tackled by soil science but also within the highly numerous disciplines of Earth and life sciences, humanities and social sciences. Soils, being as they are at the center of multiple interactions, are an intricate array of systems, a nexus joining the essential parameters. These are food, water, energy, climate and biodiversity.

Soils, in terms of structure and dynamics, with complex processes, are sensitive to global changes that induce developments, which themselves obey threshold processes and issues of resilience. These involve, with regard to their study, taking into account not only short but also long time spans. This aspect was stressed in a white paper on soils published by the CNRS in 2015 (available at the address: www.insu.cnrs.fr/node/5432). The dynamics of major biogeochemical cycles, in particular with timescale characteristics which can be centuries old, indeed even go further back beyond that and so on.

It is clear that among the major components of the environment discussed earlier, soils are the least understood by the general public, by the authorities and even in academic circles. Consequently, it becomes of prime importance to provide the conceptual bases to the greatest number of university teachers and students so as to tackle soils with the complexity of their nature, their mechanics, their diversity and their interactions with other components, within the Critical Zone.

This is what is achieved with the reflections, analyses and the prospective studies carried out by all of the authors in this series. They are top scientists with a high level of international expertise within their discipline, and are mindful of adopting a holistic approach to soil study. The authors of this series pay specific attention to aspects able to be concluded through an open interdisciplinary science, beyond the single scientific community, policy-makers, managers and to all those who are interested in the evolution of our planet. These authors also support their scientific reflection in line with training demands and, of course, the broadest dissemination of knowledge.

The series takes the form of six volumes:

–

Soils as a Key Component of the Critical Zone 1: Functions and Services,

a volume which will serve as a general introduction;

–

Soils as a Key Component of the Critical Zone 2: Societal Issues;

–

Soils as a Key Component of the Critical Zone 3: Soils and Water Circulation;

–

Soils as a Key Component of the Critical Zone 4: Soils and Water Quality;

–

Soils as a Key Component of the Critical Zone 5: Degradation and Rehabilitation;

and

–

Soils as a Key Component of the Critical Zone 6: Ecology.

Finally, it is worth mentioning again that this series was prepared essentially within the working group “Soils” at the Académie d’Agriculture de France, under the debonair, yet tenacious and assertive, stewardship of Christian Valentin. We are grateful to this group of scientists and their leader for producing this series.

André MARIOTTI

Professor Emeritus at Sorbonne University

Honorary Member of the Institut Universitaire de France

Coordinator of the series“Earth Systems – Environmental Sciences”, ISTE Ltd

1Soils as a Key Component of the Critical Zone

1.1. What are soils?

The year 2015 was the International Year of Soils, swiftly followed by the International Decade of Soils 2015–2024. Through this initiative, the UN General Assembly [UNI 13] wished to raise awareness with both civil society and policy-makers as to the crucial importance of soils in humans’ lives. Scientific, political and media interest in soils has appeared to be revived for a number of years [HAR 08a, HAR 08b]. They are now genuinely acknowledged as support for plant production and human activities, but also as an essential land-based system in the biosphere, as regulators of the major equilibria (the water cycle, and the carbon, nitrogen, phosphorous, potassium, sulfur cycles and others, which have a remarkable multi- functionality [JEF 10, GIR 11a, GIR 11b, BIS 16]). This multi-functionality of soils positions them as a key component of the Critical Zone for humanity [NRC 01, LIN 10] where life flourishes. However, do we actually know what soils are and what they do?

The word “soil” comes from the French sol, itself derived from the Latin solum, meaning ground but also base, bottom, foundation, earth, land, floor and pavement. It also means dirt, originating this time from Old French soillier meaning to make dirty. Another meaning of soil is also where one is born.

These terms are linked: in western culture, that which can be cursed – “cursed is the ground because of you” (Genesis 3:17) – is that which is dirtied by its sediment, or even upon death and burial. It is also considered as a source of all life, sphere of the gods, provider of wealth, stories and legends, patriotic pride, and other factors. Hence, the various interests, indeed contradictory, or lack of interest for this entity which feeds plants, regulates water flow and shows a fantastic biodiversity containing no doubt 25% of the Earth’s living species [DEC 10], other organisms and other biodiversity upon which we live and work. We should know that clay soils are used in pharmacopoeia (beidellite, attapulgite and smectite) for digestive disorders or in cosmetics (clay masks, hair degreasers, shampoos and other products) [LEF 11]. Do not forget that clay soils are used as construction materials (for example, adobe, tiles and bricks) and for thermal insulation. Did you know that these “soils” contain microorganisms (for example, bacteria and fungi), which produce antibiotics and vitamins and that studies of microbial population and of their antagonisms led Waksman to discover antibiotics (streptomycin) and to his Nobel Prize for Medicine in 1952 [BER 06]?

Do we know what soils are? How are they perceived? How do we define them? What is their position on the earth’s surface? How are they formed? How do their processes work? What do they do? What purpose do they serve? It is such questions to which this series of six works under the heading Soils strives to respond. This first volume, entitled Soils as a Key Component of the Critical Zone 1: Functions and Services, contains 12 chapters, including this introductory one, focused around definitions, presentations and discussions around soil properties, around the processes and services that they ensure, around the pressures by which they are influenced and the perspectives that open up. The five following works are more specialized and more detailed (Societal Issues, Soils and Water Circulation, Soils and Water Quality, Degradation and Rehabilitation and Ecology) and will approach various major aspects of soil processes and the issues that they incorporate.

1.2. The Earth, land, soils, soil cover and the Critical Zone

The semantics of the term “Earth” are vast, even without mentioning the term “ground”, which simultaneously takes account of geographical, economic and property aspects, which is hence situated at the level of the farm, the watershed or the ecosystem. The expression “field work” is analogous to “in vivo” versus “in vitro” and “laboratory study”. Man’s level of understanding is such that he rarely appreciates the layers underneath arable land. It is true that, to do this, you must plough the ground: “The harvest past, Time’s forelock take, And search with plough and spade and rake… To show by such a measure, That toil itself is treasure.” wrote Jean de La Fontaine in Le laboureur et ses enfants (The Ploughman and His Sons).

We can group the various meanings that the word “earth” takes into four different spheres:

– those attached to the Earth (with a capital letter), which comprises all of the continents and the oceans and the planet;

– those attached to the use of soils (and therefore a link with everything which is within agriculture). This may be:

- a surface area corresponding to a given land ownership – you often come across references such as “this is my land”, or “the price of land” (which depends upon its use: a forest, crop production, vineyard, second home and similar terms), and “selling his or her land”;

- a loose layer of the soil cover where plants grow: arable land, “wheat-producing land” and “unfertile land”;

- the behavior, the properties or the qualities of the surface layer used by humans: “black loam”, “soft soil”, “organic soil”, “sandy soil”, “light soil”, “soft soil”, “clayey soil, “heavy soil”, “limestone soil, “fallow soil”, “cold ground”, “poor soil”, “heathland soil”, “stony soil” and “fine soil”. Thus, according to the Scandinavian proverb, “black soil produces white bread” and the Albanian proverb “the gardeners hands are blackened with earth but his loaves of bread are white” (see

Chapters 6

and

7

: “Soils, a Factor in Plant Production: Agroecosystems” and “Forest Soils: Characteristics and Sustainability”);

– those attached to:

- clay – often confused with the term earth – as with, for example, clay used for pottery;

- construction material: “brick-earth”, “fuller’s earth” and “clay soil”;

- surface characteristics: “red earth”, “black earth”, “white earth” and other such characteristics (see

Chapter 9

: “Soils, Materials and Infrastructure Supports”);

– those linked with humanity, for example, using various expressions:

- “being known throughout the Earth”, with the term “earth” meaning the entire humanity;

- “this is my land” indicates the area characterized by the property that a given individual owns;

- “native land”, an expression which comes closer to myths, by qualifying a given space through its link with a population;

- “my ancestors’ soils” may be linked in the sense of the previous expression, but it goes further in both the mythical and generational sense (see

Chapter 10

, “Cultural Dimensions of Soils”). Soils have an archaeological memory, but also an environmental memory, which associates or distinguishes the influence and history of human and climatic activities (see

Chapter 11

: “Environmental and Societal Memories of Soils”).

Soils can be considered as entities with their own constituent characteristics or as complex natural objects, defined by their structural and functional properties and their uses.

Their definition depends upon the perception of them, their uses, their functional processes and the benefits that they provide, the given study routes and the mode of study adopted. The Larousse dictionary of the French language defines soils as the “outermost layer for the crust of a telluric planet” (Earth, Mars, the Moon, Mercury, Venus). However, there are major differences between the soils on Earth and those on Mars or the Moon, as the latter do not appear to reveal organizational structures linked to the action of living organisms. They might be able to be described as regoliths, which are formations of loose particles [DER 64], which are not fundamentally altered by the effects of living organisms.

Within this work devoted to the Earth’s soils, soils comprise this layer of the Earth where life is highly active and which we describe as the “soil cover” [GIR 11a]. This quasi-continuous, three-dimensional soil cover, which evolves from the Earth’s surface, is a key component of what was recently defined as the “Critical Zone of humanity”. This Critical Zone (CZ) has been defined by early authors [NRC 01, LIN 10] as extending from the base of aquifers to the top of plant formations. In our view, it should have, as its sub-stratum limits, unaltered mineral substrates and as its top layer the lower atmosphere, sites where life and the biogeochemical and water cycles are still significant.

The term “soil cover” insists on the fact that soils form a given part, known as the pedosphere, located on the one hand upon another part which most often has a mineral content, the lithosphere, which marries the landscape, the toposphere, and on the other hand, beneath another part which is essentially gaseous, the atmosphere, or more rarely appearing below stretches of water.

This pedosphere also interacts in time and space with two other parts: the biosphere and the hydrosphere (Figures 1.1 and 1.4) by having highly significant matter and energy exchanges (see Chapters 3–5: “Soils and the Regulation of the Hydrological Cycle”; “Soils as Bio-physicochemical Reactors” and “Soils are Biosystems, Habitats and Reserves of Biodiversity”).

Figure 1.1.The soil cover, pedosphere, at the heart of the Critical Zone of humanity, and integrating sections of other spheres (atmosphere, lithosphere, biosphere, hydrosphere and toposphere) [GIR 88]

1.3. The term “soil” has various meanings according to use and function processes

The Larousse Agricole (a comprehensive French synthesis of modern agriculture) [LAR 02] defines soil as a “natural upper loose formation of the Earth’s crust, resulting from the conversion, upon the contact of the atmosphere and human beings, with the underlying bedrock, under the influence of physical, chemical and biological processes”.

A further definition is provided by Girard et al. [GIR 11a]: “Soil is an organized structure (within various layers), which evolves, in the presence of life, and the material of which is dirt. It is the location for flow transfers, whether water, air, energy or life”.

These first two definitions must not hide the numerous other meanings of the word “soil” in current or common language [GIR 11a]. Some amusing examples can be presented here. There is, far removed from the subject of these works, the musical note (Sol in French – “So” in English). The French word sol was also a former unit of currency in France, during the early Middle Ages. In another, rarely used sense (except in physical chemistry), the term “sol” is a liquid containing dispersed matter within its given part, taking colloidal forms.

Other meanings have a closer relationship with the subject of these works, revolving around surface area, section of landscape, given territory (native soil), habitats for roots and animals and so on and will be presented and discussed hereafter.

1.4. The concept of soil varies according to the user

According to the given concerns of human societies, which have evolved over the course of their history, soils are perceived in very different ways (Figure 1.2). For over a century, the perception of soils has evolved to become almost exclusively agronomic (for example, [BER 15a, HAR 16]).

Figure 1.2.Various concepts and perceptions of the “soil” [GIR 88]

With the help of archeology, it is possible to read at least part of this history, and particularly when humanity has gone from the gathering phase to regular cultivation and onto the phase of dwelling in urban areas (see Chapter 11: “Environmental and Societal Memories of Soils”). Soils thus enable the discovery of part of human heritage.

1.4.1. Agricultural sector

Within agricultural societies which are more or less self-sufficient, soil is the means of obtaining food. For the agronomist and the forest ranger, it is designed as a resource comprising a plant nutrient reserve (whether or not this is cultivated) and a place for root growth and activity (see Chapters 6 and 7: “Soils, a Factor in Plant Production: Agroecosystems” and “Forest Soils: Characteristics and Sustainability”). It must be protected against erosion and other forms of decomposition (acidification, salinization, pollution and other factors – see volume Degradation and Rehabilitation). It is enriched with plant nutrient substances: water and fertilizers. Soil can thus be viewed as a “pantry” of a greater or a lesser size, which can be full to varying degrees for the benefit of plant life and other organisms living there. Its quality declines in the quantities of usable nutrients: what size “pantry” is required to ensure a sufficient good quality plant production, while maintaining the essential soil environmental functional processes?

1.4.2. Scientific communities

The points of view of various disciplines vary in relation to soils and may be summarized as follows. For geologists and geochemists (Allègre and Dars [ALL 09]), soil formation is a stage in the formation of sedimentary rocks.

For the geomorphologist, it is the part of the layered formations of continents transformed by living organisms and organic matter [DEW 08]. The geochemist views it as the ground compartment containing organic matter and newly formed silicate minerals (clays and oxides), which develop and constitute a stage in the formation of sedimentary rocks [ALL 09]. The climatologist views the soil as a screen which uses some of the sun’s energy and rainfall, by reflecting part of them, and which emits a given energy linked to its own surface temperature. The hydrologist (and the hydrogeologist) sees the soil as the environment which transforms precipitation into surface runoff or by infiltration and drainage transports it toward the water table, thus highly influencing both flood response times and the makeup of ground water and water courses. The ecologist perceives it as a source of transfers, production and water storage and of mineral or organic elements, a center for the food chains and organism habitats. The biologist and the microbiologist view it as a reservoir of organisms and genes of great scientific and application value. The biochemist perceives it as a reactor in which the most complex multi-enzyme reactions take place. Lastly, for the pedologist, it is a three-dimensional object, which evolves over time and creates its own organizational form (comprising its structures, layers and systems) which enables the development of life and which is rich in a very large range of plant and animal biodiversity.

1.4.3. Urban communities

For civil engineering and construction, you first have the chief surveyor, then the financier and the lawyer, who consider soil as an area to which fees, rights and obligations are attached. The geotechnical engineer, who constructs the buildings, views the soil as composed of materials of a more or less loose nature, which is situated above the bedrock. The urban planner perceives the soil as a material able to receive the foundations and the construction elements necessary for the construction of buildings [ROS 11]. For the city dweller or the sportsperson, it supports their various activities and it is where they walk or use their soccer shoes. In the view of the industrialist and the businessman, soil, which was often considered as a material resource or as plant sites, or for discharging residues or waste, is now, as with agriculture, an asset to use and manage, by applying regulations which are developed to ensure its protection, the protection of water supplies, and where its natural processes take place.

1.4.4. Current pressures and questions

Within our current societies, soils are subject to pressures, with a greater or a lesser intensity, exerted by human societies. The same societies should ensure great care in using, indeed in managing soils so as to respond to the multitude of questions and aim for harmonious and “sustainable” development of rural areas, urbanization, landscapes, plant production, water quality and other aspects.

Does the soil cover, the “epidermis” of the Earth, have the capacity to provide a protective and functional layer between the climate and its changes, water circulation and the availability of plant nutrient materials, but also for the animals and microorganisms which guarantee satisfactory operation of processes? (see Chapters 2–7 of this volume and the Ecology volume in this series).