Fundamentals of Soil Ecology

David C. Coleman, Mac A. Callaham, D. A. Crossley Jr., D. A. Crossley, Jr.

• Publisher: Academic Press
• Year: 2017
• eBook ISBN: 9780128052525
• Edition: 3
• Topic: Technology & Engineering
• Subtopic: Ecology
• Index: Technology & Engineering

Fundamentals of Soil Ecology, 3rd Edition, offers a holistic approach to soil biology and ecosystem function, providing students and ecosystem researchers with a greater understanding of the central roles that soils play in ecosystem development and function. The text emphasizes the increasing importance of soils as the organizing center for all terrestrial ecosystems and provides an overview of theory and practice in soil ecology, both from an ecosystem and evolutionary biology point of view. This new edition is fully updated, including an expanded treatment of microbial ecology and new sections on advances in molecular techniques and climate change research. These updates make this edition an essential resource for researchers and students in soil ecology and microbiology.- Includes extensive tables and diagrams in full color to enhance concepts- Combines theoretical and practical approaches to understanding and applying soil ecology- Outlines suggested laboratory and field methods

Chapter 1

Introduction to Soil

Historical Overview, Soil Science Basics, and the Fitness of the Soil Environment

Abstract

We set the stage by giving four main reasons to study soils: (1) humanity depends upon soils for their livelihood and ecosystem services; (2) as a last frontier in biodiversity research, soils teem with common and rare organisms; (3) soils are an excellent medium to study ecology ranging from organisms to ecosystems and entire regions; (4) more importantly, soils are exciting, challenging, and fun!

We present a historical background of soil concepts, extending from early Chinese and Mesopotamian cultures, through Greco-Roman, into modern times. Much modern research focuses at the interface between soil–water–gases and organisms. Soils have texture and structure, arising via a range of mechanisms, mediated by the production of soil organic matter. The hierarchical nature of soil structure leads to characteristic profiles, developing over time. The historical nature of soils extends to including “libraries” of DNA. We conclude with an introduction to soils in their provision of ecosystem services, a major theme for the entire book.

Keywords

Soil formation; physical factors; soil water; soil texture and structure; soil profiles; soils and ecosystem services

1.1 Why Soil Ecology?

A new student of soil ecology might reasonably ask the question that leads this chapter! We felt that for the third edition of Fundamentals of Soil Ecology, we should present our argument for a continued global effort toward the careful study of soil and its ecological properties. We suggest that there are at least four compelling, and somewhat interconnected, reasons for the study of soil ecology, but there are likely many more.

1. Perhaps the most compelling reason to study soil ecology in the 21st century is humanity’s dependence upon the products of soil. Current projections of human population on Earth suggest that there will be between 9.6 and 12.3 billion people on earth by the year 2100, and that this growth will continue well into the 22nd century (Gerland et al., 2014). Clearly, all of these billions will rely on food produced on agricultural soils, but the ability of the finite resource of Earth’s soils to sustainably provide the service of food production is not completely clear. Understanding the consequences of agricultural expansion or intensification will require a deep understanding of soil and its inhabitants.

2. Soil has been, and remains one of the final frontiers in biodiversity research. As a reservoir of biodiversity, soil offers an amazing opportunity to study the phenomenon of biological diversity. Because soil is by its nature immobile, it must evolve, in place, a biological community that is theoretically capable of dealing with the full set of past climatic/disturbance conditions that may have ever been experienced in a particular location. From cold and dry Antarctic soils to warm and wet tropical soils, soil everywhere harbors bacteria, fungi, and animals, which act and interact in ways that allow ecosystems to function. However, given the dramatic rate of change in climatic conditions currently underway on earth, it is unknown whether the soil biotic communities of the world’s ecosystems will have the capacity to adapt and/or evolve to novel combinations of climate, vegetation, and soil. How will soil communities respond to changes associated with human forcing of atmospheric processes? The answer will stand as a test of the importance of biodiversity to ecosystem function and the capacity of such diversity to buffer ecosystems against global change, and will be critical with regard to a continuous, sustainable supply of food and fiber for human consumption.

3. Soil is an excellent place to study ecology. In spite of the inconvenient fact that soil is a stubbornly opaque medium, it still provides opportunities to pursue nearly all the subdisciplines of terrestrial ecology: Population, Community, Ecosystem, Stoichiometry, Trophic, Agro-, Disease, Microbial, Restoration, etc. All these avenues of ecological inquiry find a home in soils, and each will be discussed throughout the text. We hope the reader will see that soil–plant–animal ecosystems provide fertile intellectual ground to plow for ecologists of all stripes (Fig. 1.1).

4. Soil ecology is fun! Even at very early ages, children become fascinated with playing in the dirt. Watch any group of children in the outdoors for long enough, and the play will take a turn toward the soil. A hole will be dug, a root excavated, a worm or beetle-grub discovered. Such discoveries elicit strong emotions whether wonder, excitement, or disgust. Children study soil in a semiscientific way, seeking for the perfect clay texture for mud-pies, or for aggregate structure that yields clods suitable for throwing at the neighbor or sibling. All this is correctly called “play,” but if the adult scientist can maintain a modicum of childlike inquisitiveness about soil and its many inhabitants, the work of soil ecology can sometimes feel like play, and is undeniably fun!

Figure 1.1 The full range of opportunities for ecological study within soil.

1.2 The Historical Background of Soil Ecology

The “roots” of human understanding of soil biology and ecology can be traced into antiquity and probably even beyond the written word. We can only imagine hunter–gatherer societies attuned to life cycles of plant roots, fungi, and soil animals important to their diets, their welfare or their cultures, and particularly to environmental conditions favorable to such organisms. Indeed, early agriculture must certainly have developed, at least in part, from a practical knowledge of soils and their physical and biological characteristics.

Soil is so fundamental to human life that it has been reflected for millennia in our languages. The Hebrew word for soil is adama, from which comes the name Adam—the first man of the Semitic religions who, in these traditions, was formed from clay (Hillel, 1991). Early civilizations had obvious relationships with soils. The Mesopotamian region encompasses present-day Iraq and Kuwait, occupying the valley of the Euphrates and Tigris rivers from their origin as they come out from the high tablelands and mountains of present-day Armenia to their mouth at the Persian Gulf. It had one of the earliest recorded civilizations, the Sumerian, dating from about 3300 years BCE (Hillel, 1991). An inventory taken in the time of the early Caliphates showed 12,500,000 acres (nearly 5,100,000 hectares) under cultivation in the southern half of Mesopotamia (Whitney, 1925). With many centuries of irrigation, this so-called hydraulic civilization was plagued with problems of siltation and salinization, which was written about at the time of King Hammurabi (1760 BCE) (Hillel, 1991). An impressive sequence of civilizations waxed and waned over the millennia: Sumerian, Akkadian, Babylonian, and Assyrian, as cultivation shifted from the lower to central and upper regions of Mesopotamia. Siltation and salinization continue to beset present-day civilizations that practice extensive irrigation-based agriculture with examples worldwide (Rengasamy, 2006).

To the east of Mesopotamia, past the deserts of southern Iran and of Baluchistan, lies the Indus River Valley. Another irrigation-based civilization developed here, probably under the influence of the Mesopotamian civilization. The Indus River civilization probably encompassed a total land area far exceeding that of either Sumeria or Egypt; little is known about it. No written records have been discovered, but its fate, like that of the Sumerian, succumbed to environmental degradation, exacerbated by the extensive deforestation which occurred to provide fuel to bake the bricks used in construction (Hillel, 1991). The bricks in Mesopotamian cities were sun-baked, similar to the adobe style of construction used in the deserts of the southwestern United States.

In contrast, the Egyptian civilization persisted more or less in place, as a result of the annual floods of the Nile River, which renewed soil fertility in vast areas along the river’s length as it flowed northward. Over the millennia, from 1 to 3 million people lived along the Nile, and produced enough grain to export wheat and barley to many countries around the Mediterranean rim. Now that the population is some 30 times greater, it must import some foodstuffs and is economically in questionable condition, in spite of the vast areas being irrigated with water from the Aswan high dam.

The ancient Chinese concept of fundamental elements included earth, air, fire, water, and moon. In the Yao dynasty from 2357 to 2261 BCE, the first attempt was made at soil classification surveying. The Emperor established nine classes of soils in as many provinces of China, with a taxation system based upon this system. These classes included the yellow and mellow soils of Young Chow (Shensi and Kansu); the red, clayey, and rich soils of Su Chow (Shantung, Kiangsu, and Anhwei); the whitish, rich salty soils of Tsing Chow (Shantung); the mellow, rich, dark, and thin soils of Yu Chow (Honan); the whitish and mellow soils of Ki Chow (Chili and Shansi); the black and rich soils of Yen Chow (Chili and Shantung); the greenish and light soils of Liang Chow (Szechuan and Shensi); and the miry soils of King Chow (Hunan and Hupeh) and Yang Chow (Kiangsu) (Whitney, 1925). This system reflects a sophisticated knowledge within early Chinese civilization of soils and their relationship with plant growth. Interestingly, in recognition of the importance of biological activity in soils, the ancient Chinese termed earthworms as “angels of the soil” (Blakemore, 2002).

The Greeks believed there were four basic elements: earth, air, fire, and water; and Aristotle, understanding the role of earthworms in organic matter decomposition, considered earthworms to be the “intestines of the earth” (Edwards and Lofty, 1977). In Greek mythology, the champion of mortal men, Heracles, defeated Antaeus, perhaps symbolically ushering in the age of man’s dominion over the soil. A wild and dangerous giant, Antaeus, who was the son of Gaia (goddess of the earth), was invincible so long as he maintained physical contact with the soil, but Heracles recognized this and lifted the gia...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Preface
• Chapter 1. Introduction to Soil: Historical Overview, Soil Science Basics, and the Fitness of the Soil Environment
• Chapter 2. Primary Production Processes in Soils: Roots and Rhizosphere Associates
• Chapter 3. Secondary Production: Activities of Heterotrophic Organisms—Microbes
• Chapter 4. Secondary Production: Activities of Heterotrophic Organisms—The Soil Fauna
• Chapter 5. Decomposition and Nutrient Cycling
• Chapter 6. Soil Food Webs: Detritivory and Microbivory in Soils
• Chapter 7. Soil Biodiversity and Linkages to Soil Processes
• Chapter 8. Future Developments in Soil Ecology
• Chapter 9. Laboratory and Field Exercises in Soil Ecology
• References
• Index