Gardening, Siskiyou

Soil is life

As a soil scientist for 33 years, I never really thought about the long history of soils on earth. I just focused on Siskiyou County’s forest soils. Siskiyou County has the most soil diversity compared to anywhere else in the United States. This is because our soil forming factors are extremely diverse. Our rainfall varies from 10 to 100 inches. Our elevations vary from 600 feet near Somes Bar to over 14,000 feet on Mt Shasta. Our landform slopes range from flat to extremely steep. Our geology includes granite, ancient sea sediments, serpentine, peridotite, lava flows, volcanic ash, stream and glacial deposits. 

Earth began to form around 4.54 billion years ago (; Aug 20, 2021). Earth’s soils occurred around 3.8 billion years ago when liquid water first condensed and starting eroding the Earth’s rocky crust (; Dec 1, 2020). Life in Earth’s oceans began around 3.8 billion years ago. These early microscopic organisms may have migrated to land as cyranobacteria around 3.5 billion years ago and formed surface soil crusts (; Dec 1, 2020). They were not the same as today’s soils. Soil formation at that time was controlled by parent material, topography, climate and time. These soil materials formed from the breakdown of rocks by physical and chemical processes. They were basically mineral particles of various sizes and voids containing gasses, mainly methane, nitrogen and carbon dioxide. These early soils lacked animals and organic matter. These soils, resembling current Martian soils, came and went for 3 billion years. 

Fungi appeared on land around 1.3 billion years ago with land plants, such as mosses and liverworts, appearing on land about 700 million years ago. (; Aug 8, 2001). Plants and soils became even more closely linked when plants developed roots some 400 million years ago (; Aug 8, 2021). At this point, an essential part of the plant is entirely within the soil. This was the beginning of processes that created soils like we have today. Today’s soil forming factors are parent material, topography, biotic component (plants, animals), climate, and time. The earliest known land animal was a species of millipede, which lived 428 million years ago (; Sept 23, 2015).

Today’s earth consists of the above ground, the below ground, and ocean ecosystems. These three ecosystems interact with each other in varying degrees. The above and below ground ecosystems have the strongest interaction and dependency on each other. Both systems have atmosphere, water, organic matter, vegetation, solid mineral matter and animal life as macro-and micro-organisms. Terrestrial ecosystems are linked to ocean ecosystems by runoff water that carries nutrients and pollutants and delivers them to the ocean. 

Perhaps the most important property of soils is porosity. The pores among the tiny soil particles make soil act as a sponge. This means that soils can hold water against the force of gravity. This soil water is stored and available for plants to use during times when rain does not fall.

Soil also acts like an organism; in that it breathes. Pores contain both water and air, with soil air constantly mixing with atmospheric air.

Because terrestrial life evolved with soils, there can be no life without soil and no soil without life. Soil serves as the foundation for much of Earth’s biodiversity. The soil ecosystems control the processes essential for plant growth.  

In our modern soils, plants and soil communicate with each other (; plant communication). Plants send out chemical signals using soil microbes as a delivery service. Plants read the local environment and, when necessary, make and release molecules called flavonoids. These molecules attract microbes that infect the plant’s roots and form nitrogen-producing nodules in the roots, in other words, they generate plant food. 

To find the best path forward, scientists say, we need to listen to signals that soils are sending, good or bad. Plant growth is dependent on the amount of food and water the soil has that is available to plants, just as a person requires food and water to survive and grow.  Cut back on either and growth slows down.   

Because your life literally depends on soil, treat it like your friend. Be kind to it, helping it when it needs help, and protecting it when needed. For soil to be your friend you must learn about it, respect it, and keep your eyes and mind open. 

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