The Secret Life of Soil

By Bryan Medina, Community Organizer (Southeast Los Angeles)

Hello TreePeople!

Many of us know that our plants and trees help to increase shade, retain rainwater, and promote biodiversity to our region.

However, none of this would be possible without good ol’ soil! Soil is incredibly important because it acts a bit like a sponge absorbing as much water and nutrients as possible for plants and trees.

From there, flora can take sips of water as needed; this is especially important for our native and climate-appropriate plants and trees since Los Angeles doesn’t get a whole lot of rainfall.

In many places around LA, much of our flora hasn’t been getting as much water as they need because of impermeable surfaces — surfaces like concrete, gravel, and artificial turf — where water isn’t allowed to reach plant roots and instead flows to storm drains. If the soil is dry and compacted, plants are likely to not thrive and can’t help increase shade and biodiversity we need!

You might be wondering what makes soil such an amazing resource for our local flora and fauna. Healthy soil is usually made up of natural ingredients such as:

Sand, Silt, and Clay

All three of these materials contain rocks and minerals that vary in size and composition. Sand is usually the coarsest with silt then clay being the finest. Soil characteristics often vary by region.

Organic Matter

Organic matter includes any decaying material such as leaves, bark, fallen branches, plants, or animals. As time goes by, this material becomes humus, which is brown-colored and rich in carbon; a perfect source of nutrients!

Air and Water

Both air and water are found in pockets between soil particles where roots can tap into.

These critters also help keep our soil healthy!

Bacteria and Fungi

Bacteria and fungi are like nature’s recycling and clean-up team! Bacteria are so small and make up the most organisms in the soil (at least 250,000 of them can fit inside this dot: •). Bacteria can only consume so much organic material but they get help from fungi, which can break down more complex matter and can even penetrate hard surfaces!

Algae

Algae is usually associated with bodies of water but they can also thrive in moist soil too! Algae are single-celled organisms and primitive forms of plants, meaning they can absorb carbon dioxide and release oxygen. In the right conditions, algae can grow and create a slime that bonds soil particles.

Protozoa and Nematodes

Sometimes, in healthy soil, bacteria and fungi can grow to a point where there’s too many of them and not a lot of food sources to go around. Protozoa and nematodes help to keep these populations in check and can turn the nutrients from them into minerals that plants can use to grow and thrive.

Arthropods, Gastropods, and Earthworms

Our forests and gardens are alive with insects, spiders, and all sorts of invertebrate friends. These critters help to eat organic material and the crumbs are left for fungi and bacteria to eat too. These little guys also help microbial life hitch a ride around the soil and aerate the soil when they dig underground, helping with the regrowth of plant root and delivery of water and minerals.

Mammals, Reptiles, and Birds

Our bigger animal friends help create healthy soil via their droppings, which provide food for microbial life. When they pass on, their bodies are decomposed and absorbed into the soil.

Healthy soil not only helps keep our plants and trees grow and thrive but also support complex food webs for other animals in the community. It’s also important to know that without healthy soil in LA, much of our plant life isn’t able to provide us with shade, better resources to fight industrial pollution and flooding, places to mentally and physically recharge, or the wonderful native wildlife we share our unique home with.

Los Angeles-based TreePeople is the region’s largest environmental movement, whose mission is to inspire, engage and support people to take personal responsibility for the urban environment. Visit us at treepeople.org and learn how you can join our cause.