(The following is from my monthly newsletter. This series began in March 2022 and has continued for nearly a full year, with its final installment in February 2023. Below is the “better” edited version from what I originally emailed to my followers.)

Capturing solar energy means taking advantage of the energy that is emitted by the sun and turning it into usable energy for life. The only organisms on terrestrial earth (aside from cyanobacteria) capable of such a feat are plants.

Ecosystems are Powered by the Sun

Plants capture the sun’s energy to feed other life forms. They do this through a process called photosynthesis. Plants have evolved to turn solar radiation into energy via specialized cellular organs called chlorophyll. Some scientific research has theorized that plants formed a mutual relationship with cyanobacteria billions of years ago. Eventually, evolution turned this relationship into a reduced form of bacteria within each of a plant’s cells.

Natural ecological evolution has enabled animals to take advantage of the energy provided by the plants by eating them; other animals ate those other animals, and so on. Such is the natural food web, which basically reflects the energy pyramid we’ll see soon.

As we are in the business of food production, we also take advantage of the energy provided by plants to feed ourselves and our animals (which will eventually feed us). The caveat is in how we are able to capture that sunlight and put it to use. The question how is in the way our management decisions can maximize solar energy capture as much as the ecological system we live in allows.

To achieve that, we need to understand how energy flow occurs.

The energy pyramid

The traditional energy pyramid, as shown above, displays how energy flows upwards as various trophic levels. Plants are the first and bottom level, and decay is the final (top) level. In between is the function of life feeding upon each other, from herbivores up to apex predators including us humans.

At each trophic level, energy is lost as heat. That heat is a result of cellular metabolism. Energy is also lost in the expulsion of waste. With a loss of energy, there tends also to be a loss of biomass at each level.

What the traditional pyramid does not show, though, is what goes on below ground. Plants not only feed animals above ground with the sacrifice of their leaves, stems, flowers, and seeds. They also feed organisms below ground with their roots.

As above, so below.

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However, this second version of the energy pyramid is still the “outdated” version. It is the 2D version that does not show how our management impacts the ability to capture more solar energy–or even less.

Introducing, the energy tetrahedron.

The Volumetric Change to the Energy Pyramid

The energy tetrahedron is a new way of looking at the energy pyramid. The tetrahedron changes our view from the 2D “triangle” where all we see is how energy is lost, to the 3D pyramid (or, tetrahedron) that shows us the volume of energy produced for the life of this planet by plants. It still acknowledges that energy is being lost, but it’s a drastic change in perception because now we can see just how management increases or decreases the base (or middle) of the shape by three major factors:

1. Time
2. Density
3. Area

Basically, if we can expand any one of the three sides of that tetrahedron, we are able to increase the volume of the amount of solar energy captured, and therefore increase the volume of harvestable energy at all levels on the energy pyramid. However, if we shorten any one side, we decrease the amount of solar energy captured, therefore decreasing the amount of harvestable energy at all levels of the energy pyramid.

Let’s discuss those three sides, and how our management can expand them.

The Three Sides

Time:

The “Time” side of the energy tetrahedron can be expanded by extending the amount of time plants spend growing throughout the season. Basically, the longer plants spend growing, the greater the productivity of the stand. And the greater the productivity of the stand, the more solar energy can be captured.

Lengthening the growing season gives plants more time to grow. The timing of when those plants are grazed and how long of recovery period they get plays a big role. If they’re grazed to where they’re growing even to freeze up and snow cover, they will often remain green even though the cold forces them into a state of dormancy.

What better way to collect solar energy than with green, photosynthetic solar panels otherwise known as leaves? The more leaves there are, the better the solar energy capture!

Density:

“Density” on the energy tetrahedron is in the context of the number of plants per square foot to maximize solar energy capture, which correlates to the number of leaves covering the surface. The greater the density of leaves, the more solar energy is captured.

Think of it like a forest. The forest is where multiple canopies exist to maximize solar energy capture; trees, then shrubs, then forbs and some grasses. The open grassland or pasture will be fairly similar, with canopy layers not as noticeable. We usually have to lie down on our stomachs to see these layers in a healthy grassland.

Basically, the whole premise is that if the stand is dense with lots of leaves and lots of plants, more energy is going to be captured which means more forage available for the animals to graze.

Area:

The “Area” on the energy tetrahedron is also known as the “leaf area.” Leaf area refers to the amount of surface area available for solar energy capture. Basically, the wider and broader the leaves, the more energy is captured as opposed to narrow, fine leaves.

In order to maximize leaf area, plants must be kept in the optimum growth stage (see graph below). This means harvesting plants before they’ve had a chance to go into flower, allowing them time to recover, and repeating the process again. Most solar energy capture happens when lots of leaf material is green and present. Little solar energy capture happens when there’s little leaf material present, or when most of that leaf material is browning down and dying.

Basically, from the graphic above, our best time to capture solar energy is not when quality is highest or when yield is highest, but when they both meet at the point which is considered optimal. That’s when the plants are in their “Phase 2” stage, where the most leaf material is put out after they’ve surpassed Phase 1 and are nearly, but not quite, ready to start on to Phase 3 of their life cycle.

Remember too, that it’s not just grasses and legumes that are great at solar energy capture. Even weeds are great at it too. Even though they’re more unsightly and aren’t growing where you want them to, they’re still plants and are still equally capable of capturing solar energy (and carbon) to feed the soil and feed animals.

Speaking of feeding biology, for next time: nutrient cycling.