37,82 €
Mehr erfahren.
- Herausgeber: Bentham Science Publishers
- Kategorie: Lebensstil
- Sprache: Englisch
Soil Biology & Ecology: The Basics offers an accessible introduction to the diverse and dynamic world beneath our feet. This book explores soil as a thriving habitat, detailing the rich biodiversity of microorganisms and macroorganisms that sustain essential ecological cycles. It covers the key biochemical cycles in soil, including carbon, nitrogen, phosphorus, and sulfur, explaining how these processes contribute to soil fertility and ecosystem health. With a focus on ecological relationships like symbiosis and competition, this guide illuminates the vital role of soil in supporting life and agricultural productivity.
Ideal for students, researchers, and nature enthusiasts, the book is a foundational resource for understanding soil's impact on the biosphere and human food production.
Key Features:
- Comprehensive overview of soil as a living ecosystem
- Detailed coverage of soil microbiota, macrobiota, and biochemical cycles
- Insights into ecological relationships and their practical applications
Readership:
Suitable for students, researchers, and general readers interested in natural sciences
Das E-Book können Sie in Legimi-Apps oder einer beliebigen App lesen, die das folgende Format unterstützen:
Seitenzahl: 173
Veröffentlichungsjahr: 2024
Ähnliche
BENTHAM SCIENCE PUBLISHERS LTD.
End User License Agreement (for non-institutional, personal use)
This is an agreement between you and Bentham Science Publishers Ltd. Please read this License Agreement carefully before using the book/echapter/ejournal (“Work”). Your use of the Work constitutes your agreement to the terms and conditions set forth in this License Agreement. If you do not agree to these terms and conditions then you should not use the Work.
Bentham Science Publishers agrees to grant you a non-exclusive, non-transferable limited license to use the Work subject to and in accordance with the following terms and conditions. This License Agreement is for non-library, personal use only. For a library / institutional / multi user license in respect of the Work, please contact: [email protected].
Usage Rules:
All rights reserved: The Work is the subject of copyright and Bentham Science Publishers either owns the Work (and the copyright in it) or is licensed to distribute the Work. You shall not copy, reproduce, modify, remove, delete, augment, add to, publish, transmit, sell, resell, create derivative works from, or in any way exploit the Work or make the Work available for others to do any of the same, in any form or by any means, in whole or in part, in each case without the prior written permission of Bentham Science Publishers, unless stated otherwise in this License Agreement.You may download a copy of the Work on one occasion to one personal computer (including tablet, laptop, desktop, or other such devices). You may make one back-up copy of the Work to avoid losing it.The unauthorised use or distribution of copyrighted or other proprietary content is illegal and could subject you to liability for substantial money damages. You will be liable for any damage resulting from your misuse of the Work or any violation of this License Agreement, including any infringement by you of copyrights or proprietary rights.Disclaimer:
Bentham Science Publishers does not guarantee that the information in the Work is error-free, or warrant that it will meet your requirements or that access to the Work will be uninterrupted or error-free. The Work is provided "as is" without warranty of any kind, either express or implied or statutory, including, without limitation, implied warranties of merchantability and fitness for a particular purpose. The entire risk as to the results and performance of the Work is assumed by you. No responsibility is assumed by Bentham Science Publishers, its staff, editors and/or authors for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products instruction, advertisements or ideas contained in the Work.
Limitation of Liability:
In no event will Bentham Science Publishers, its staff, editors and/or authors, be liable for any damages, including, without limitation, special, incidental and/or consequential damages and/or damages for lost data and/or profits arising out of (whether directly or indirectly) the use or inability to use the Work. The entire liability of Bentham Science Publishers shall be limited to the amount actually paid by you for the Work.
General:
Any dispute or claim arising out of or in connection with this License Agreement or the Work (including non-contractual disputes or claims) will be governed by and construed in accordance with the laws of Singapore. Each party agrees that the courts of the state of Singapore shall have exclusive jurisdiction to settle any dispute or claim arising out of or in connection with this License Agreement or the Work (including non-contractual disputes or claims).Your rights under this License Agreement will automatically terminate without notice and without the need for a court order if at any point you breach any terms of this License Agreement. In no event will any delay or failure by Bentham Science Publishers in enforcing your compliance with this License Agreement constitute a waiver of any of its rights.You acknowledge that you have read this License Agreement, and agree to be bound by its terms and conditions. To the extent that any other terms and conditions presented on any website of Bentham Science Publishers conflict with, or are inconsistent with, the terms and conditions set out in this License Agreement, you acknowledge that the terms and conditions set out in this License Agreement shall prevail.Bentham Science Publishers Pte. Ltd. 80 Robinson Road #02-00 Singapore 068898 Singapore Email: [email protected]
PREFACE
Atlhough few people acknowledge it, soil is one of the environments hosting the highest biodiversity on this planet. A multitude of micro-and macroorganisms, bacteria, fungi, protists, plants and animals populate the various types of soil.
Yet, a really remarkable thing about soil is not just its enormous biodiversity, but also the variety and complexity of interactions among present organisms. At this level, we can find complex symbioses, competition, predation and parasitism. These interactions are essential to the continuous recycling of bioelements, in decomposing organic matter and making available again its various components.
Thus, soil has a crucial contribution to the very existence of Earth’s biosphere. It provides nutritional support to all land-based ecological communities and, is also the basis of any agricultural production, thus, of our everyday food.
This is why knowledge of all these aspects of soil biology and ecology is important to naturalists. This book is conceived as a guide to students, specialists and all people interested in natural sciences.
Soil as a Living Habitat, General Considerations
Dan Răzvan PopoviciuAbstract
Soils cover most of the Earth’s landmasses. Soil is a complex system, under continuous evolution and in perpetual relation to the atmosphere, hydrosphere, lithosphere, and biosphere. It is polyphasic, composed of a solid (mineral and organic) fraction, but also of liquid and gaseous fractions. A key aspect is its stratification into several horizons. This complex structure determines the living conditions being provided to the local biota, but also a major diversification of soil types on our planet.
INTRODUCTION
Understanding soil biota requires, first of all, understanding soil as a living environment.
The key aspects of this are defining and delineating soil from other environments, knowing its characteristics, its structural features, and the life conditions it offers to inhabiting organisms.
Defining Soil
A key issue in studying this environment is how to clearly define and delimit it.
According to the Soil Science Society of America, soil can be briefly defined as “The unconsolidated mineral or organic material on the immediate surface of the earth that serves as a natural medium for the growth of land plants” [1].
The same society also gives a more precise definition, stating that soil is “The unconsolidated mineral or organic matter on the surface of the earth that has been subjected to and shows effects of genetic and environmental factors of climate (including water and temperature effects), and macro- and microorganisms, conditioned by relief, acting on parent material over a period of time” [1].
According to this definition, soil consists of both organic and inorganic components, which are subjected to continuous transformations, due to various
environmental factors specific to our planet. Thus, the soil is clearly distinct from the regolith covering the surfaces of other planets in our Solar System – a layer of variable thickness, made up of mobile mineral fragments, but devoid of organic matter (or, at least not in substantial amounts), lifeforms and lacking exposure to a hydrosphere or even atmosphere [2].
Natural Resources Conservation Service (government entity subordinated to the United States Department of Agriculture), defines soil as “Soil is a natural body comprised of solids (minerals and organic matter), liquid, and gases that occur on the land surface, occupies space, and is characterized by one or both of the following: horizons, or layers, that are distinguishable from the initial material as a result of additions, losses, transfers, and transformations of energy and matter or the ability to support rooted plants in a natural environment.” [3].
Thus, the soil is formed of diverse components, has its specific layering, and is under continuous evolution, but it is also characterized from a functional point of view, by its ability to support plant life. The latter is connected to a key feature, typical to soil, that makes it clearly distinct from non-soils: fertility.
Even more important, NRCS states there are some physical boundaries between soils and other environments. The upper limit is the interface between the soil and air or a shallow water layer.
In aquatic environments, it is necessary to distinguish soil from sediments (sand, mud, etc.). The arbitrary limitation, according to NRCS is that the water layer should be less than 2.5 m thick so that the underlying material could be considered as soil. This would correspond to the maximum insertion limit of rooted water plants [3].
It is also important to define the lower limits of soil. Unlike underlying materials, the soil is characterized by a continuous interaction with the atmosphere and hydrosphere. Most lifeforms (including plant roots) dwell within a thin layer of Earth’s lithosphere. This although there are living beings (mostly microorganisms) that can be found up to 5 km deep [4].
So, as a practical maximum lower limit, soil scientists take a depth of 2 m [3].
Soil Characteristics
There are several key features that define soil:
• Soil is a system. This means that it includes various types of components, integrated in a functional ensemble.
• It is a natural system because it is formed under the influence of natural, biotic, and abiotic factors.
• It is complex because the factors conditioning its genesis and structure are numerous.
• It is polyphasic, its genesis involves different successive temporal stages.
• It is heterogeneous, being formed of components having different physical states (mainly solid, but also liquid and gaseous).
• It is polydisperse, meaning that its solid phase – dominant – is found under different degrees of dispersion: coarse dispersions (suspensions: sand and dust grains), colloidal dispersions (such as some heavily soluble hydroxides, humus, and clay), and molecular/ionic dispersions (soluble salts).
• It is an open system, being constantly involved in matter and energy exchange processes with Earth’s lithosphere, hydrosphere, atmosphere, and biosphere.
• It is a polyfunctional system, performing multiple functions [5].
Morphological Characterization of Soil
As a complex system, soil is made up of different components. This complexity can be seen, for instance, in its vertical stratification (as soil consists of several horizons).
Horizon succession usually follows the scheme shown in Fig. (1) (obviously, this is a general model, while variations can occur from one soil type to another; some horizons may be missed, while others are present).
Thus, we may successively encounter:
• O horizon, superficial, rich in organic matter. It is mostly developed in forest areas, as well as in some grasslands (pastures, prairies). Its presence is due to plant tissue decomposition (especially leaves from woody plants). It can be subdivided into three categories, or sub-horizons, depending on the degree of organic matter decomposition: plant litter (Ol), fermentation horizon (Of), and humification horizon (Oh).
• A horizon, also called surface horizon or topsoil, contains a mix of organic and mineral matter.
Fig. (1)) The main horizons that compose a typical soil profile according to Science Facts [6].• E horizon has a low content of clays, iron and/or aluminium compounds and stable minerals. It is formed through eluviation (“leaching”) of the mineral content by water. On the other hand, it is enriched in silica.
• B horizon (subsoil) is the layer where clays, metal oxides, etc. coming either from the bedrock or from upper horizons (if present), or even formed in situ tend to accumulate. Usually, iron oxides give it a reddish color.
• C horizon is a mineral one, with low or zero organic matter content and a low influence on atmospheric, hydrospheric, or biospheric processes. This is where carbonates coming from upper horizons tend to crystallize.
• R horizon is the bedrock. Depending on geographical location, it can be found at a depth of a few centimeters or a few meters below the surface [7].
Each horizon can have subdivisions and there can also occur specific horizons (P horizon – peanut, specific to peatlands, G horizon – gleic, saturated with water, etc.) [5], that make the object of pedology.
In characterizing soils, an important aspect is their structure, which allows for distinguishing several types of soils. Structure is given by the assembly, or lack of assembly of component particles into aggregates. Thus, there are glomerular, granular, prismatic, polyhedric angular and subangular, columnar, lamellar soils, etc. A good soil structure is considered to be the one that allows air and water to permeate (Fig. 2) [5].
Fig. (2)) Soil types according to structure and permeability to water [8].Considering the composition, a typical soil is made up, on average, of around 50% solid matter (45% being mineral and just 5-10% organic matter). The remaining 50% (40-60%) consists of interstitial spaces (pores), where the gaseous fraction (air) and the liquid one (water) are hosted, each forming 20-30% of the total mass [9].
Thus, any soil is formed of the following components:
• Solid inorganic matter (dominant), comprising both rock fragments and primary minerals (derived from rock disaggregation) and secondary minerals formed due to the weathering of primary ones.
• Solid organic matter, comprising dead organisms, under different stages of decomposition (but also, obviously, living microorganisms) and organic substances newly synthesized at soil level (humic compounds, or simply humus).
• Soil solution (water containing variate amounts of dissolved mineral salts). Soil water can be found in the following forms: hygroscopic water (with a strong physical bound, due to adhesion forces, to soil grains), pellicular water (weakly bound, covering soil grains), capillary water (contained in soil pores) and gravitational water (free, easily replenished due to rain, easily accessible to plants, but also easy to be lost through leaking and evaporation), of which a fraction sinks towards more profound soil layers [5, 7].
• The gaseous component is, basically, air coming from the atmosphere, but with a somewhat different composition, due to specific biological or chemical processes. Thus, soil air usually contains 78.5-80% nitrogen (compared to 78% in the atmosphere), 10-20% oxygen (compared to 21%), 0.2-3.5% carbon dioxide (in the atmosphere 0.04%), also hosting relatively large amounts of water vapor, hydrogen sulfide, methane, ammonia [5].
Another key aspect is texture. Soil texture is due to the distribution of various granulometric classes of soil particles, of which we can mention gravel (grains over 1 mm in diameter), sand (0.01-1 mm, with various subclasses), dust, mud, and colloids, commonly known as clays (a component made up of grains below 0.01 mm and chemically active).
According to texture, we can distinguish sandy, sandy-loamy, loamy-sandy, loamy, loamy-clayey, clayey-loamy, clayey, and heavy clayey soils [5].
Finally, another important consideration in soil characterization is water content. Soils can be unsaturated (liquid water does not fill interstitial spaces completely), saturated, or even flooded (water level is above the upper soil interface; (Fig. 3). This is an extremely important aspect, that regulates oxygen permeability and the distribution of soil microbiota.
Fig. (3)) Water saturation levels of soil [10].Soil Classification
Soil classification is done according to several criteria.
One of the most important is the presence, absence, degree of development, and succession of the above-mentioned horizons. However, other factors and pedogenetic processes matter too (Fig. 4).
Fig. (4)) A few types of soil [11].Classifications may vary, according to the different pedological schools, but, basically, we may distinguish among major units such as the chernozems, phaeozems, kastanozems, luvisols, planosols, podzols, umbrisols, cryosols, cambisols, vertisols, calcisols, gypsisol, solonetzes, solonchaks, gleysols, etc., each with its corresponding subclasses [5].
From a practical point of view, the most important classification criterion is fertility and agricultural potential, with chernozems (steppe soils) ranking among the highest (Fig. 5).
Fig. (5)) The global distribution of the main soil types [12].Environmental Factors Influencing Life in the Soil
Among the main factors are:
• Temperature is an extremely important factor, influencing liquid water availability, solubility and diffusion of various nutrients, enzyme functioning, etc. Each organism has its own thermal optimum and its own degree of tolerance to values outside this optimal range. Basically, except for some hot volcanic soils, most types of soil worldwide fit into the general biological optimum of 0-60°C [13].
• The pH of soil solution is also important for the availability of certain mineral nutrients, also affecting some biological processes. Just as for temperature, each species has its own pH optimum. Regular variation limits are between 3 and 8.5. Most organisms, especially multicellular ones (animals, plants), are sensitive to extreme values [13].
• Salinity refers to the concentration of salts dissolved in soil solution. It affects the ability of living organisms to absorb water and may cause osmotic stress and osmotic shock to sensitive species.
• Moisture, meaning the water content of the soil has both a direct influence on life (water is a key resource to all metabolic processes) and also an indirect one, determining soil oxygenation or the mobility of certain microorganisms.
• The mineral composition is important, minerals being valuable nutrients for organisms; however, some may become toxic when in excess.
• Organic matter provides a nutritive substrate to heterotrophic organisms.
• Light is particularly important to photosynthesizing organisms. The other living beings are indirectly affected, through the thermal effect of sunlight (infrared radiation) or the disruptive effects of ultraviolet radiation, which makes some organisms require chemical (specific pigments) of microtopographic (taking shelter in/beneath pebbles, etc.) screening.
• Pollution is a factor of growing importance nowadays. Among the most damaging pollutants are hydrocarbons, including their halogenated or hydroxylated derivatives (compounds derived from the breakdown of plastic, industrial solvents, etc.), heavy metals, various pesticides in excess, etc. Pollutants can be inorganic, such as heavy metal compounds, that are generally damaging to the cell structures of all organisms, when in excess. However, there are extremely numerous classes of organic pollutants, deriving from fuels, solvents, paints, cleaning and disinfecting products, pesticides, antibiotics and other pharmaceuticals . There are many ways in which such compounds can affect soil life. Some (like hydrocarbons) lower soil permeability to oxygen and water. Others are directly toxic to living organisms. Others have a selective effect on soil microbiota, inhibiting some organisms while stimulating others, thus influencing the way soil functions as a system. While pollution can affect the diversity and distribution of soil microbiota, its most visible effects are on the flora and fauna [13, 14].
All these factors vary at a global level. Some of these variations can be seen in a latitudinal or altitudinal gradient, determining a characteristic zonation of vegetation, but also of associated soil types (Fig. 6). Other variations are present at a local level, causing significant differences in life conditions over distances of a few meters or even less.
Fig. (6)) Altitudinal [15] and latitudinal [16] ecological zones.CONCLUSION
Soil is a complex type of environment, covering most of the Earth’s landmasses. It is composed of both inorganic and organic fractions and its existence is due to micro- and macrobiota.
It is made up of specific layers, has a diverse structure and, besides the solid components, also contains a liquid fraction (soil solution) and a gaseous one.
