The Biosphere

The Biosphere - SQA Key definitions : 

• Bio-crude oil - A biofuel produced by heating wet biomass (such as algae) under high pressure to produce an artificial crude oil. 

• Biodiesel - A biofuel produced by combining vegetable oil or animal fat with an alcohol.

• Bioethanol - A biofuel produced by the fermentation of sugars from plant materials using microorganisms to break down the complex sugars into ethanol.

• Biofuel - Combustible biomass or fuels derived from biomass. 

• Biological weathering - The structural breakdown of rock by living organisms. For example, a plant's roots grow down into rock, and the rock can be broken apart as the roots grow and expand in size.

• Biomethanol - A biofuel produced from biomass or organic waste instead of fossil fuels. 

• Brown earth soil - Deep, well-mixed, nutrient-rich soil, found under deciduous woodland.

• Capillary action - The movement upwards of water through a mixture of adhesion (water molecules sticking to the surface of soil particles) and cohesion (water molecules sticking to each other).

• Chemical weathering - The structural breakdown of rock by chemical action caused by naturally occurring carbonic acid in rainwater, dissolving rock. 

• Climate - The long-term atmospheric or weather conditions of an area. 

• Decomposition - The breaking down of organic matter into simpler inorganic and organic compounds. 

• Eluviation - When rainfall exceeds evapotranspiration, water moves downward through the soil profile, carrying away dissolved minerals, nutrients, and suspended soil particles.

• Humification - The transformation of raw organic material (like dead leaves, roots, and microbes) into humus, a complex, dark-colored organic substance.

• Illuviation - Water from upper layers washes minerals, nutrients and soil particles into a lower soil layer, forming a nutrient-rich region

• Leaching - The process by which soluble substances (like mineral salts or plant nutrients) are dissolved and carried downward through the soil by percolating water as part of eluviation.

• Parent material - The original rocks or minerals from which that soil is produced. 

• Physical weathering - The structural breakdown of rock by repeated cycles of warm and cold temperatures, breaking down rock through the 'Freeze-Thaw' process. 

• Podzol soil - Shallow, nutrient-poor soil in well-defined layers, found under coniferous woodland.

• Pore space - The distribution and arrangement of the empty spaces (pores) within the soil.

• Processed biofuel - A fuel produced from plant material, usually requiring a large amount of processing to make it usable. 

• Relief - The elevation, steepness and aspect (which way it's facing) of a location. 

• Soil profile - The vertical cross-section of the layers of soil at a location. 

• Soil structure - The arrangement of the soil's primary particles (sand, silt, and clay) and organic matter into clumps or groups called aggregates.

• Soil texture - The proportions of 'Sand', 'Silt' and 'Clay' within the soil. 

• Translocation -  The lateral (sideways) and vertical movement of soil materials within the developing soil profile. 

• Weathering - The structural breakdown of rock due to physical, chemical & biological processes. 

The Biosphere 

The Biosphere consists of all of the the organic (living) material that is present on the Earth. This incudes the organic material below the surface deep in the soil, as well as land and aquatic life, as well as organic material within the atmosphere. The Biosphere includes the all organic material, from the largest animals such as the Blue Whale, to the smallest single-celled organisms such as bacteria.

Soil : Inputs

Soil is a very complicated material that forms the base structure of the majority of the land on Earth : 

The key factors which affect soil formation are : 

• Parent Material - The size and type of the original mineral grains determine the soil's texture (the proportion of sand, silt, and clay) and how water and air move through it.

• Organisms - Organisms physically break down parent material and mix the soil layers, leading to deeper, more uniform soil profiles.

• Relief - The elevation, steepness of slopes and aspect (which way it's facing) affect the movement and accumulation of water, which is fundamental to soil chemistry and biological activity. 

• Climate - Climate affects the speed and nature of the weathering of the parent material and the decomposition of organic matter.

• Time - Time dictates how long other factors have to affect the soil. This determines the maturity or development stage of the soil. 

Soil Formation : Weathering

Weathering is the breaking down of rocks on the Earth's surface. It is a key component in soil formation as it provides the raw materials for the soil, which are then further changed by organisms.  

There are three key ways that weathering can occur:-

Soil Formation : Decomposition and Humification

There are two key organism types that play a vital role in soil formation: detritivores and decomposers. 

Both detritivores and decomposers play a role in decomposition (the breaking down of organic matter into simpler inorganic and organic compounds) and humification (The transformation of raw organic matter into humus, the organic component of soil). 

The initial decomposition process is the physical breakdown of the material, which is performed by detritivores like earthworms, mites, and millipedes. They break down large pieces of dead organic material (like leaf litter and wood) into smaller fragments, increasing their surface area. This allows the decomposers to chemically break down the organic matter at the molecular level through enzymatic action. 

This process is vital to life on land as it releases essential plant nutrients that are locked up in dead biomass, making the soil fertile. Without decomposition, nutrients would remain trapped in dead leaves and wood, starving the next generation of plants. The humus produced is an active part of the soil, forming a long-term store of nutrients, as well as increasing the water-holding capacity of the soil and binding the soil together. 

Soil Formation : Translocation

The movement of materials through the soil is also a vital component of soil formation. This process, known as 'Translocation', is the lateral (sideways) and vertical movement of soil materials within the developing soil profile (the vertical cross-section of the layers of soil at a location)  :  

There are 4 key translocation processes which cause the layering found within the soil profile : 

Soil Composition

As previously stated, soil structure will depend greatly on the parent material, the organisms present within it and the relief of the land itself. This means that soil in different locations can have very different compositions. 

The proportions (and therefore impact on the soil) will be different, but all soil is composed of a blend of the following constituents :

• Mineral matter, from the disintegration and decomposition of rocks.

• Organic matter, from the decay of plant residues, animal remains and microbial tissues.

• Water, from the atmosphere and reactions in the soil (chemical, physical and microbial)

• Air or other gases, from the atmosphere and from reactions of roots, microbes and chemicals in the soil.

• Organisms, both macro (worms, insects) and micro (bacteria, etc.)

Soil Composition : Soil Texture

The proportions of 'Sand', 'Silt' and 'Clay' determine the soil's texture : 

 The three (required at Higher Level) classifications of 'Sand', 'Silt' and 'Clay' are based on particle size : 

The difference in soil 'feel' is caused by the combination of the particle size and a soil's 'pore spacing', the distribution and arrangement of the empty spaces (pores) within the soil. This, in turn, affects how water can be held within or move through the soil, as well as how gases can pass through it : 

Soil Composition : Soil Structure 

The proportions of 'Sand', 'Silt' and 'Clay' determine the soil's texture, but how those particles are arranged within the soil determines the 'Soil structure'. The 'soil structure' is the arrangement of the soil's primary particles (sand, silt, and clay) and organic matter into clumps or groups called aggregates.

Unlike the 'soil texture', which is fixed by the composition of the soil, the 'soil structure' can be easily improved or damaged by land use and management practices. 

Examples of soil aggregates are shown below :  

The soil structure can be damaged by a range of land use practicies. The damage occurs when the stable clumps of soil (aggregates) are broken apart, or when the pores between them are lost. This damage reduces the soil's ability to support life, exchange air, and manage water. 

The two main risk factors that cause this damage are : 

There are several land use practices that will improve soil structure. These focus on preventing the damage from occuring through the limiting use of machinery to a bare minimum, using sustainable Tilling practices and incoporating organic matter into the soil to replace organic matter lost through decompositon. 

Soil Composition Case Study : Brown Earth Soil

'Brown Earth' soils are found across Scotland, below deciduous woodland. As this type of woodland drops its leaves in winter, a deep layer of decaying matter forms on the surface, giving a soil rich in humus. 

This humus is acted upon by soil organisms, like earthworms, which mix the materials, merging the boundaries between the layers and giving the soil an overall brown colour. 

A low level of leaching means that no eluviated layer forms, making 'Brown Earth' soils nutrient-rich throughout the soil profile. 

Due to its high nutrient content through deep layers of the soil, 'Brown Earth' soils are commercially used for : 

Soil Composition Case Study : Podzol Soil

The word 'Podzol' comes from the Russian roots : Pod (пoД) - meaning 'under' or 'beneath' and  Zola (зола) - meaning 'ash', due to the characteristic ash-coloured layer found beneath the topsoil.

'Podzol' soils are found across Scotland, below coniferous woodland in upland areas. As this type of woodland is evergreen, there is only a thin layer of decaying matter that forms on the surface, which is acidic due to the decaying conifer needles. 

As the soil is acidic, there are relatively few organisms, like earthworms, which would mix the materials, so the soil remains in clearly defined layers. 

A high level of leaching occurs, creating a deep ash-grey eluviated layer, which is very low in nutrients. Iron compounds leach downwards and can accumulate to form a thin layer of 'hardpan' (a chemically cemented, rock-hard layer), which impedes drainage through the soil and through which roots cannot grow. This shallowing of the root systems is why conifer forests are more likely to be damaged by storms than deciduous forests, due to the lack of anchoring. 

Some other metal compounds can pass downwards through this layer, giving the layer below a reddish brown colour. 

Due to its acidic, low nutrient content, shallow soil, 'Podzol' soils are commercially used for : 

Soil Scientists gather, interpret and evaluate information about the structure and quality of soil. This is then used to influence practices such as agricultural and horticultural production, habitat management and forestry.

Soil Scientists assess the soil’s ability for growing crops, recommend land management methods to prevent landslide erosion and can advise on environmental issues, tackling problems such as the pollution and acidification of soils by chemicals and heavy metals.

Biofuels

Biofuels are fuels that have been made from plant material, usually requiring a large amount of processing to make them usable. 

They are split into two categories : 

• First-Generation - Created from edible sources (food that humans or animals could eat).

• Second-Generation - Created from waste materials or non-edible plants. 

Biofuels : First-Generation

First-generation biofuels are created from edible sources, and are currently the most common type of biofuel because the technology to process them is simple and well-proven. 

Biofuels : Second-Generation

First-generation biofuels are created from waste materials and non-edible sources, and are designed to solve the sustainability problems of the first-generation biofuels.