NATURE NOTE - Number 90                                                                                              April 14 , 2024                    

Introduction:  Welcome back to NATURE NOTES.  Thanks for reading these NOTES and I hope you will find a way to pass some of this information on to your scouts. 

We know that the distribution of plants all around the world is heavily dependent on climate; different plants need various amounts of water, heat, and sunlight to thrive or even grow.  But a lesser known, lesser observed and seldom discussed factor is ….

Our Current topic:   Geobotany  -  and a little soil science

What is geobotany?  This refers to the ability to determine what plants will grow on different soils.  Since soils are derived in part from the minerals and rocks that make up that soil, there is a connection between the plant and the geology underlying or providing soil for an area.  The soil that you see under your feet is probably soil and minerals that have been blown or washed into your location from somewhere else by erosion over many, many years.  But regardless of its origin, the soil contains different minerals that will impact the soil and plant species.  Some of these minerals are nitrogen, phosphate, potassium, calcium, sulfur and magnesium.  These will influence the pH factor, or acidity, of the soil.  If you reach back into your high school biology or chemistry class, you may remember that pH is a way of measuring the acidity of something, such as water or soil.  Some plants grow best in slightly acidic soil (pines for example), while others do best in soil that is more neutral.  Let’s review the pH scale and what it means.  (This may be too much for young scouts, and older ones may know all of this from school.)  A pH factor of 7.0 is considered neutral.  An example is distilled water.  As the number goes below 7.0, the water or soil becomes more acidic.  Some examples:  Saliva is about 6.5 on the scale; coffee is 5.0; and lemon juice and vinegar have a pH of 2.  As the number goes the other way, above 7.0, it is more alkaline (or basic).  Examples:  baking soda is 9.5; and bleach is 13.  The number is a measure of the free hydrogen ions in the water – some chemistry we won’t go into here.  While most trees will grow in a rather wide range of pH values, many trees seem to grow best in neutral (pH of 7) or slightly acidic soil (6 or so), while others tolerate a slightly alkaline soil  The higher PH favors species such as Silver maple, Black locust, and Bald cypress.  As mentioned above, pines, Rhododendron and Sweet Gum can do well in soil with a lower pH (slightly more acidic).  Obviously, the pH level is a factor for all plants, not just trees.  While all of this may not be particularly useful to scouts, it does show how plants are influenced by the soil and geology that surround them.  Something not commonly considered when discussing plant growth.  Maps of soil pH and underlying minerals can be used to help determine the likely, or perhaps the optimal species for that area, after considering temperature, rainfall, and sun light.  This also shows the importance of soil analysis in your garden as you try to grow flowers or vegetables.  Urban soil is usually on the slightly higher end of the pH scale.  In an agriculture setting, or your lawn, fertilizers can alter the soil in your favor if you know what you need to correct.  Farmers usually use fertilizers showing some numerical makeup, such as 10-10-10, meaning that the fertilizer contains that percent of available nitrogen, phosphate, and potassium (potash). For example, a 100 pound bag of 10-10-10 would have 10 pounds each of nitrogen, phosphate, and potassium. The other 70 percent is filler. 


A good, easy to find example of this geobotany, is to observe old pastures you might see along a highway.  If you see a lot of small red cedars growing there, and maybe not many other trees, there is a real good chance that this old field has a lot of limestone as its base.  You might even see some rock outcroppings.  Red cedar seems to thrive on substrata providing lots of calcium.  Another example can be found in a forest made up of mostly pine trees.  These trees grow best on an acidic soil, but this condition often is not favorable to other plants.  Falling needles simply adds more acid to the soil, and over time, you will see less and less other plants growing under the trees.  There is also less sunlight available to these smaller plants as well.  Remember that deciduous trees (those that lose their leaves in the fall) will often leaf-out later in the spring allowing sunlight to reach the smaller plants on the forest floor and allow them to start their grow earlier.  Later they can exist on more filtered sunlight.   

All of this just shows that there are many factors that contribute to plant growth, and how all of nature is closely connected; the geology impacts the soil that impacts trees and other plants, and on and on.  If your scouts can be made aware of all of these connections, and perhaps see some real world examples, they will be ahead of most of their contemporaries and well on their way to appreciate all of the complexity of the natural world.  Do what you can, and thanks for what you do.

Bob Garst

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