What is soil and why does it matter?

I love soils, and all the animals that live in and on top of it. I spent most of my undergraduate work focusing on soil ecology and working both in the lab and in the field on projects related to arthropods, earthworms, and soils in forests and urban areas. This summer I am working at Black Rock Forest located in Cornwall, New York, an amazing research and teaching forest, where I will be collecting soils and the arthropods and assessing the effects of forest disturbances on these soil-dwelling animal communities. Before I describe my research project, I want to share why soil is so important, though it is often undervalued and under-appreciated.

IMG_3381Photo: Black Rock Forest, October 2013

Soil sustains life on Earth. People often take for granted that soil exists beneath their feet. Soil is not only important for healthy forests and crops but they provides habitat for a huge variety of organisms. Let’s say you walk into a forest or a garden or a field and scoop up a handful of dirt. What would you find? At first, you would probably just think you had simple handful of uninteresting material that just help prop up plants and trees. In reality, you have a complex mixture of chemical compounds and animals that make up one of the most important mediums in an ecosystem.

The soil you are holding has been in the making for a long time. Soil does not just appear. Over time, based on the parent material, which is the rock type you start out with on your landscape, the climate acts on the soil: rain and wind changes the chemistry of the rock. The scientific processes that describe the changes from rock to soil are called leaching and weathering. These processes alter the chemistry of the rock so that the compounds from the rock, mixed with the organic compounds from the surface, turn into what we recognize as soil.

When you reached down and grabbed your handful of soil, it was most likely exposed and easy to pick up. Because soils are directly in contact with the air, there are many exchanges between soil and atmosphere. Plants take in carbon dioxide (CO2) during photosynthesis and use the carbon to live. When a plant dies, the carbon in that plant is recycled into the soil and through complex chemical reactions, soil releases that carbon into the atmosphere. Most people are familiar with carbon because of carbon dioxide and its emissions in the atmosphere contributing to human-caused global climate change. In fact, CO2 emissions from soil are the greatest contributor to atmospheric COHowever, it’s important to remember that soils are a natural source of CO2, as opposed to the many anthropogenic sources.

IMG_3377Photo: Black Rock Forest, October 2013

What else is in the soil in your hand? You’ve likely picked up a living organism or two that you can easily identify, like an ant or an earthworm. You might assume that’s all that’s living in your hand. Most of these organisms are small, like little mites or springtails about a millimeter in size or even smaller on the microscopic scale, like a fungus or bacteria. Soil is one of the most important habitats for a wide variety of organisms from burrowing mammals to crawling arthropods to basically invisible microorganisms. All organisms in the soil not only transform their soil habitat by creating holes or burrows through which water can flow but they also provide services for each other. For example, certain organisms eat dead plant material and by eating this dead material, they change the form of the material – what we would call nutrients – so that new growing plants can take that transformed material and use them to grow. This is called nutrient recycling. By maintaining this natural nutrient recycling process, soils can continue to supply nutrients to plants and animals.

hypvia01Photo: Collembola or springtail, only a few millimeters in size from www.collembola.org

When you think less about biology and ecology and more about sustainability and agriculture, soils become arguably even more important. The biological health of soils is tightly linked to social and economic issues today. Something that people often forget is that soils are the medium in which we grow many of our crops. Food production depends heavily on soils and the nutrients in them, referred to as soil fertility, which is why we care so much about fertilizers and the general chemical composition of soils. Current threats to soils include degradation, erosion, and contamination. As discussed previously, soils taken many hundreds of years to develop and current practices are not favorable for maintaining healthy soils.

The scoop of soil you originally picked up should now appear to be a complex assortment of different elements and organisms. This medium is the keystone of most forests, agricultural land and habitats. All of the complex processes in soil provide numerous services and contribute to global biodiversity. Recognizing what soil is and what how incredible it is will help to prevent further damage to this indispensable resource.

 

-Natalie Bray