What is Soil?
To most, soil is just the ground beneath our feet, but soil is a complex mixture of minerals, organic matter, and organisms. With the TREE program, you will need to provide samples of soil near the trembling aspen you are sampling from. Soil is collected because it helps correlate data from the tree cores because as we know, soil is composed of many nutrients and minerals that find their way into the tree. By analyzing the soil, we are able to potentially make these connections and see the impact the environment has on the tree.
Soil contains the three common states of matter: solid, liquid, and gas. Roughly 50% of soil is solid and is composed of minerals (~45%) and organic matter (~5%). Soil is porous though which allows for water and gases to seep through (see Figure 1). Soil has four main functions. It acts as a medium for plant growth. It also stores and filters water. Soil also modifies the atmosphere by emitting and absorbing various gases and dust. Finally, soil is also a habitat for countless organisms. These functions continuously alter the composition and structure of soil.
All of the soil on Earth is collectively called the pedosphere. As outlined in Figure 2, the pedosphere connects to the four other spheres: the lithosphere (Earth's crust and upper mantle), the hydrosphere (Earth's water and ice), the atmosphere (Earth's gases), and the biosphere (Earth's living creatures).
Figure 1 shows the pores or spacing between sand grains. Image by klaber.
Figure 2 shows the interconnectedness of Earths many spheres. Original image by Jojndon.
How is Soil Different from Dirt?
The terms soil and dirt are used interchangeably but they are, in fact, different and should be used separately. Dirt is distinct from soil in that dirt is soil that has been displaced from its native environment in a way that is unusable. Dirt is incapable of supporting plant growth, so it is sometimes referred to as dead soil. You can identify dirt from soil by adding water to it. If the mixture compacts well together, it is soil. If the mixture does not pack together, then it is most likely dirt.