MEETING REPORT: October 2021, Robin Kobaly, The Desert Underground

By Donna Mallen, for Let's Talk Plants! November 2021.

Among the new frontiers of scientific research and discovery in recent history is an overlooked dimension previously invisible to the human eye – the living soil beneath our feet. The “biocrust” – the biological soil crust that we humans were seeing every day of our lives without recognizing that it was alive, and the extensive and interactive community of plant roots, fungi, bacteria and algae in motion below ground, are now understood to be critical to plant and animal life (including ourselves) above the surface.

The underground community of organisms, acting in partnership to support each other, is now being explored by scientists with the aid of microscopes, satellite mapping, growth ring measurements, soil core sampling to determine the depth of roots, and other tools unavailable in the past.

Amazing new discoveries are being made. For example, in the Mojave Desert, it has been determined that the average age of the common Creosote bush, found throughout the deserts and chapparal of Southwestern ecosystems, is 600 to 1,000 years, with some particular plants having tested out at over 10,000 years! The roots of desert plants can extend 2 to 10 times as deep as the plant is tall.

All over the world, researchers studying the mycorrhizal activity that occurs underground have learned the critical connection between living plants and the reduction of carbon in our atmosphere. In partnership together, the plants and fungi are removing carbon from the atmosphere as they grow and storing the carbon underground even after the death of the living organisms, so long as the soil is not disturbed.

These are the scientific facts that Robin Kobaly, a botanist and plant ecologist, was called upon to report to the Riverside County Board of Supervisors for their consideration in deciding an issue of solar panel farm placement, informing them of the consequences if undisturbed land on the Mojave Desert floor were to be scraped to allow room for solar panels.

She cautioned the Supervisors that disturbing the soil and killing the plants could cause damage that may take hundreds or thousands of years to reverse. The Supervisors listened and took heed, revising the plan accordingly.

Her brief book, The Desert Underground, beautifully and informatively illustrated by ecologist and artist Dr. Juniper Harrower, was originally prepared as a visual aid to the presentation to the Riverside County Board, and is now available online at

In her presentation to us, Robin effectively broke down the complex scientific details, using pages from the book in her PowerPoint slides, and gave us a whole semester’s worth of soil science and ecology in one meeting. For me, it was so intriguing that I bought the book online during her presentation.

She explained in depth the process by which the plants capture carbon from the air, convert it to sugars, and send it to their roots during photosynthesis. Below ground, fungal threads surrounding the plant’s roots connect with nodes on the roots to reach the carbohydrate nutrients that the plant shares with them. The fungi are highly absorbent and are storing water in the soil that surrounds the plant roots. In this mutually beneficial partnership, the plants are able to obtain and utilize the moisture and nutrients they need from the arid desert soil, and the fungi are able to obtain the nutrients they are unable to produce for themselves.

Also at these root nodes, the carbon dioxide breathed out by the plants reacts with calcium in the soil to form caliche, or calcium carbonate, which acts like cement to hold the carbon in undisturbed soil.

Delving down another level into the microbial activity involved within the mycorrhizal partnership, modern science continues to discover new information about the microscopic creatures and processes that are going on beneath us.

For instance, out of the carbon received from the plant roots, the fungi construct mycelium strands coated with a sticky outer sheath of a protein called glomalin, which waterproofs the threads within and continues to hold the carbon even 30 to 100 years after the death of the fungal threads.

Scientists estimate that glomalin stores one-third of the world’s soil carbon, and that the amount of carbon stored throughout the world in caliche may be equivalent to the total amount existing in our atmosphere.

In our search for solutions to the increase in carbon in our atmosphere, we can be an above-ground partner to the underground community that has already been protecting the planet over the millennia, by supporting and sustaining this amazing hidden resource.

Donna Mallen is the most recent member to join the San Diego Horticultural Society Board. She is in charge of meeting programing for the 2022 - 2024 term. She lives and is retired in San Diego.