Understanding Soil Systems and Ecosystems

This movie covers Subtopic 5.1, Introduction to Soil Systems, under the main IBESS Topic 5, Soil Systems and Society. Significant idea number one from this subtopic is, the soil system is a dynamic ecosystem that has inputs, outputs, storages, and flows. You need to be able to outline the transfers, transformations, inputs, outputs, flows, and storages within soil systems. Storages include organic matter, organisms, nutrients, air, and water. Transfers include biological mixing, translocation, which is the movement of soil particles in suspension, and leaching, which is minerals dissolved in water moving through the soil. Inputs include organic material, including leaf litter, inorganic, material from parent material, precipitation and energy. Outputs include uptake by plants and soil erosion. And transformations include decomposition, weathering, and nutrient cycling. Stop the video and study this slide to make sure you understand and can do an outline of these various components of a system. The soil has been allotted its own sphere, the petosphere. which is the thin bridge between the biosphere and the lithosphere, and is acted upon and influenced by the atmosphere, the hydrosphere, and the lithosphere. You need to be able to explain how soil can be viewed as an ecosystem. Recall that an ecosystem is a community and the physical environment it interacts with. Soil is a complex ecosystem. It is made up of minerals, organic material, gases and liquids, all of which form habitats for many animals and plants. There are many ecosystem services provided by the soil. Climate regulation, nutrient cycling, habitat for organisms, food regulation, source of pharmaceutical and genetic resources, foundation for human infrastructure, provision of construction materials. cultural heritage, provision of food, fiber and fuel, carbon sequestration, and water purification and soil contaminant reduction. Soil is made up of four main components. Mineral particles, mainly from the underlying rock, organic matter, organic remains that have come from the plants and animals, water within spaces and between soil grains, and air within the soil grains. As already mentioned, it provides habitat for plants and animals. Soil is highly porous with a 50-50 mix of solids and pore spaces, and the pore spaces contain variable amounts of water and air. The mix of these four components give soil its character. Here are some functions of the different fractions of soil. The rock particles, provides skeleton of the soil and it's derived from underlining rock or rock particles transported to the environment. There are insoluble and soluble rock particles. The soluble rock particles contain mineral salts, compounds of nitrogen, phosphor, potassium, sulfur, and magnesium. Hummus gives soil its dark color and as it breaks down it returns minerals and nutrients back to the soil. It absorbs and holds on to water. and it is made of plant and animal material that is in the process of decomposition. Water dissolves mineral salts and moves them through the soil so that they become available to plants. It moves downward causing leaching and upward causing salinization. This is called translocation. Large volumes of water can cause water logging and avoid anoxic conditions and acidification. So water seeps down from precipitation or moves up from underground sources. Air provides oxygen for respiration of soil organisms and plant growth. And mainly it is oxygen and nitrogen. The soil organisms themselves. The small invertebrates break down large particles of dead organic material. Then the microorganisms decompose those small molar particles. Recycling nutrients. Large animals such as moles help mix and aerate soils through burrowing. So soil organisms include the soil invertebrates, the microorganisms, and larger animals. When we take a cross-section of soil, we can observe the soil profile, which is called horizons. Not all soils contain the top three horizons, and sometimes we can't dig deep enough to find the C layer. However, generally speaking, these are the soil horizons. The O horizon contains partially decomposed... organic matter, and fungi, bacteria, and animals start to decompose the dead material. The A horizon is the top soil or upper layer. Decomposition is incomplete here, giving the soil its dark color called humus. The E horizon is the zone of leaching, and materials move downward, resulting in depletion of organic matter at this horizon. The B horizon is the subsoil where where iron, aluminum, iron, and humus compounds are accumulated, and clay is leached down from horizons A through E above, resulting in enrichment of clay and iron salts in this region. The C horizon is weathered parent material, or weathered rock, and the R horizon is the bedrock, or parent material. The mineral portion of the soil can be divided up into three parts. particles based on size, sand, silt, and clay. Sand particles are between 0.05 and 2 millimeters in diameter. Silt particles are between 0.002 and 0.05 millimeters in diameter, and clay particles are less than 0.002 millimeters in diameter. The proportion of these particles gives soil its texture. Most soils contain a mixture of different soil particles. If a fairly equal portion of each size is present, then the soil is said to be loam. Loam describes the structure of soil. Loam contains a mixture of clay, silt, and sand. Knowing the percentage of each particle in the soil, you can use a soil texture triangle, pictured here, to determine the type of soil that you have. Qualitatively, when you feel the soil, sandy soils are gritty and fall apart easily. Silty soils are slippery and hold together better than sandy soils, and clay soils feel sticky and can be rolled up easily into a ball. A quantitative measure of texture is to pass dry soil through a series of sieves of decreasing mesh size which will separate the soil into its portion of clay, silt, and sand particles. You can calculate the percentage of each particle from this separation. Another method is to mix the soil with water and allow the particles to settle, and then calculate the percentage of each particle. With both of these techniques, then, you can refer back to the soil texture triangle to determine the type of soil that you have. Porosity contributes to soil quality. Porosity is the amount of space between particles, which then contributes to the permeability, or the ease at which gases and liquids can pass through the soil. It is important that water neither rushes through the soil nor settles at the surface. Gases and liquids need to pass gently through the soil, carrying minerals and nutrients. The pH of the soil also contributes to soil quality, and it is important because nutrients can be locked by soil minerals if the soil pH is not correct. This affects whether the plant can use the nutrient or not. Either low or acidic pH or high or alkaline pH can affect the availability of nutrients. pH also influences soil bacteria, nutrient leaching, and soil structure. You need to be able to compare and contrast the structure and properties of sand, clay, and loam soils with reference to a soil texture diagram, including their effect on primary productivity. We've already looked at the soil texture triangle and worked with it in class. Let's look at structural properties. Clay is heavy and hard. The grains of clay are very tiny and therefore can squeeze tighter together. the soil is compact and difficult to drain sand is the opposite of clay it is much lighter and larger grains the grains of sand in comparison of clay cannot squeeze nearly as close together and therefore allow more water to drain through it sand barely holds on to water at all and tends to be very dry silt sits somewhere between clay and sand on the grain spectrum they are closer together to hold on to a bit of water with enough space in between to allow for some drainage silt tends to be a more gummier soil and is often found at the bottom of lakes. Loam is a combination of all three, and is traditionally 40% sand, 40% silt, and 20% clay. Loam has more nutrients, moisture, and humus than sand. Loam also has better water movement, and is much easier to work and till. A natural loam is the preferred soil for growing plants, as it retains water and nutrients far for the plants, better than any individual component. on its own. This table shows you the differences between sand, silt, and clay with regards to nutrient capacity, infiltration, water holding capacity, aeration, and workability. Be aware of the different properties these soil particles contribute to soil structure and function. Sand, silt, and clay are combined in different percentages to yield many different types of soil all over the world. Also contributing to different soils is climate, the parent rock material, the shape of the land, organisms living within the soil, and time. It's complex. This image simply gives you a visual of different biome soils. Significant idea number two, the quality of soil influences the primary productivity of an area. Recall from our discussions on succession that it takes hundreds of years to develop a climax community and that this is dependent on the develop and build up of soil. The better the quality of soil, the higher the productivity. As you recall during primary succession productivity is low. Soil quality is low. As organisms die and decay, soil is built up over time, giving higher and higher quality of soil, thus contributing to increased productivity. Soil giving rise to high productivity is what we call fertile soil. Fertile soil has enough nutrients for healthy plant growth. Fertile soil has the main nutrients, which are nitrates, which contribute to plant growth phosphates which contribute to root system and production of fruits and vegetables and potassium which regulates stomata opening and closing therefore regulating co uptake these main nutrients are the mpk many micronutrients are also needed by plants and therefore are found in fertile soil nutrients can be leached out of the soil or removed when a crop is harvested and they must be replaced in agricultural soils. This can be done using chemical fertilizers, growing legumes, through crop rotation, or through the application of organic matter such as manure and compost. It is important that you understand that soil is a non-renewable resource. Why? Remember, it takes hundreds of years to make soil. Therefore, if we destroy it or allow it to degrade or erode, We can't have more the next day or month or even year. Therefore, we must save our soils through policies, education, and sustainable practices. Here is a summary of Subtopic 5.1. This ends the movie for IBESS Topic 5.1, Introduction to Soil Systems, under the main topic of IBESS Topic 5, Soil Systems and Society. The slides were created by me, Dr. Nina Markham. Image sources are indicated with a citation under the image. If all images on the slide are from the same source, the source is simply cited at the bottom of the slide. Another resource for you is your IBESS textbook, whether in hardback form or online, such as Cognity. Thank you for listening.

Storages include organic matter, organisms, nutrients, air, and water. Transfers include biological mixing, translocation, which is the movement of soil particles in suspension, and leaching, which is minerals dissolved in water moving through the soil. Inputs include organic material, including leaf litter, inorganic, material from parent material, precipitation and energy. Outputs include uptake by plants and soil erosion. And transformations include decomposition, weathering, and nutrient cycling.

Stop the video and study this slide to make sure you understand and can do an outline of these various components of a system. The soil has been allotted its own sphere, the petosphere. which is the thin bridge between the biosphere and the lithosphere, and is acted upon and influenced by the atmosphere, the hydrosphere, and the lithosphere.

You need to be able to explain how soil can be viewed as an ecosystem. Recall that an ecosystem is a community and the physical environment it interacts with. Soil is a complex ecosystem. It is made up of minerals, organic material, gases and liquids, all of which form habitats for many animals and plants.

There are many ecosystem services provided by the soil. Climate regulation, nutrient cycling, habitat for organisms, food regulation, source of pharmaceutical and genetic resources, foundation for human infrastructure, provision of construction materials. cultural heritage, provision of food, fiber and fuel, carbon sequestration, and water purification and soil contaminant reduction.

Soil is made up of four main components. Mineral particles, mainly from the underlying rock, organic matter, organic remains that have come from the plants and animals, water within spaces and between soil grains, and air within the soil grains. As already mentioned, it provides habitat for plants and animals.

Soil is highly porous with a 50-50 mix of solids and pore spaces, and the pore spaces contain variable amounts of water and air. The mix of these four components give soil its character. Here are some functions of the different fractions of soil. The rock particles, provides skeleton of the soil and it's derived from underlining rock or rock particles transported to the environment. There are insoluble and soluble rock particles.

The soluble rock particles contain mineral salts, compounds of nitrogen, phosphor, potassium, sulfur, and magnesium. Hummus gives soil its dark color and as it breaks down it returns minerals and nutrients back to the soil. It absorbs and holds on to water. and it is made of plant and animal material that is in the process of decomposition.

Water dissolves mineral salts and moves them through the soil so that they become available to plants. It moves downward causing leaching and upward causing salinization. This is called translocation.

Large volumes of water can cause water logging and avoid anoxic conditions and acidification. So water seeps down from precipitation or moves up from underground sources. Air provides oxygen for respiration of soil organisms and plant growth.

And mainly it is oxygen and nitrogen. The soil organisms themselves. The small invertebrates break down large particles of dead organic material.

Then the microorganisms decompose those small molar particles. Recycling nutrients. Large animals such as moles help mix and aerate soils through burrowing.

So soil organisms include the soil invertebrates, the microorganisms, and larger animals. When we take a cross-section of soil, we can observe the soil profile, which is called horizons. Not all soils contain the top three horizons, and sometimes we can't dig deep enough to find the C layer. However, generally speaking, these are the soil horizons.

The O horizon contains partially decomposed... organic matter, and fungi, bacteria, and animals start to decompose the dead material. The A horizon is the top soil or upper layer. Decomposition is incomplete here, giving the soil its dark color called humus.

The E horizon is the zone of leaching, and materials move downward, resulting in depletion of organic matter at this horizon. The B horizon is the subsoil where where iron, aluminum, iron, and humus compounds are accumulated, and clay is leached down from horizons A through E above, resulting in enrichment of clay and iron salts in this region. The C horizon is weathered parent material, or weathered rock, and the R horizon is the bedrock, or parent material. The mineral portion of the soil can be divided up into three parts. particles based on size, sand, silt, and clay.

Sand particles are between 0.05 and 2 millimeters in diameter. Silt particles are between 0.002 and 0.05 millimeters in diameter, and clay particles are less than 0.002 millimeters in diameter. The proportion of these particles gives soil its texture. Most soils contain a mixture of different soil particles.

If a fairly equal portion of each size is present, then the soil is said to be loam. Loam describes the structure of soil. Loam contains a mixture of clay, silt, and sand. Knowing the percentage of each particle in the soil, you can use a soil texture triangle, pictured here, to determine the type of soil that you have. Qualitatively, when you feel the soil, sandy soils are gritty and fall apart easily.

Silty soils are slippery and hold together better than sandy soils, and clay soils feel sticky and can be rolled up easily into a ball. A quantitative measure of texture is to pass dry soil through a series of sieves of decreasing mesh size which will separate the soil into its portion of clay, silt, and sand particles. You can calculate the percentage of each particle from this separation. Another method is to mix the soil with water and allow the particles to settle, and then calculate the percentage of each particle. With both of these techniques, then, you can refer back to the soil texture triangle to determine the type of soil that you have.

Porosity contributes to soil quality. Porosity is the amount of space between particles, which then contributes to the permeability, or the ease at which gases and liquids can pass through the soil. It is important that water neither rushes through the soil nor settles at the surface.

Gases and liquids need to pass gently through the soil, carrying minerals and nutrients. The pH of the soil also contributes to soil quality, and it is important because nutrients can be locked by soil minerals if the soil pH is not correct. This affects whether the plant can use the nutrient or not.

Either low or acidic pH or high or alkaline pH can affect the availability of nutrients. pH also influences soil bacteria, nutrient leaching, and soil structure. You need to be able to compare and contrast the structure and properties of sand, clay, and loam soils with reference to a soil texture diagram, including their effect on primary productivity. We've already looked at the soil texture triangle and worked with it in class. Let's look at structural properties.

Clay is heavy and hard. The grains of clay are very tiny and therefore can squeeze tighter together. the soil is compact and difficult to drain sand is the opposite of clay it is much lighter and larger grains the grains of sand in comparison of clay cannot squeeze nearly as close together and therefore allow more water to drain through it sand barely holds on to water at all and tends to be very dry silt sits somewhere between clay and sand on the grain spectrum they are closer together to hold on to a bit of water with enough space in between to allow for some drainage silt tends to be a more gummier soil and is often found at the bottom of lakes.

Loam is a combination of all three, and is traditionally 40% sand, 40% silt, and 20% clay. Loam has more nutrients, moisture, and humus than sand. Loam also has better water movement, and is much easier to work and till. A natural loam is the preferred soil for growing plants, as it retains water and nutrients far for the plants, better than any individual component. on its own.

This table shows you the differences between sand, silt, and clay with regards to nutrient capacity, infiltration, water holding capacity, aeration, and workability. Be aware of the different properties these soil particles contribute to soil structure and function. Sand, silt, and clay are combined in different percentages to yield many different types of soil all over the world. Also contributing to different soils is climate, the parent rock material, the shape of the land, organisms living within the soil, and time. It's complex.

This image simply gives you a visual of different biome soils. Significant idea number two, the quality of soil influences the primary productivity of an area. Recall from our discussions on succession that it takes hundreds of years to develop a climax community and that this is dependent on the develop and build up of soil. The better the quality of soil, the higher the productivity. As you recall during primary succession productivity is low.

Soil quality is low. As organisms die and decay, soil is built up over time, giving higher and higher quality of soil, thus contributing to increased productivity. Soil giving rise to high productivity is what we call fertile soil.

Fertile soil has enough nutrients for healthy plant growth. Fertile soil has the main nutrients, which are nitrates, which contribute to plant growth phosphates which contribute to root system and production of fruits and vegetables and potassium which regulates stomata opening and closing therefore regulating co uptake these main nutrients are the mpk many micronutrients are also needed by plants and therefore are found in fertile soil nutrients can be leached out of the soil or removed when a crop is harvested and they must be replaced in agricultural soils. This can be done using chemical fertilizers, growing legumes, through crop rotation, or through the application of organic matter such as manure and compost. It is important that you understand that soil is a non-renewable resource.

Why? Remember, it takes hundreds of years to make soil. Therefore, if we destroy it or allow it to degrade or erode, We can't have more the next day or month or even year.

Therefore, we must save our soils through policies, education, and sustainable practices. Here is a summary of Subtopic 5.1. This ends the movie for IBESS Topic 5.1, Introduction to Soil Systems, under the main topic of IBESS Topic 5, Soil Systems and Society.

The slides were created by me, Dr. Nina Markham. Image sources are indicated with a citation under the image. If all images on the slide are from the same source, the source is simply cited at the bottom of the slide. Another resource for you is your IBESS textbook, whether in hardback form or online, such as Cognity. Thank you for listening.

Transcript for:Understanding Soil Systems and Ecosystems

Transcript for:
Understanding Soil Systems and Ecosystems