“Plants are amazing!” This is something I hear a lot from non-botanists. Of course, I know plants are awesome, but every time I turn around, I learn something new and exciting. This semester was no exception. Tasked with a project in my Biomimetic Design class, led by Dr. Petra Gruber, I walked into the meadow to find inspiration– literally.
On a very wet, cold, rainy day in October, I walked to a meadow within our field station property (Bath Nature Preserve, Bath Twp., Akron, Ohio) and found a section to investigate. Indian grass (Sorghastrum nutans) towering over my head, I decided to stop at 20 steps and set up a 1m x 1m plot to sample. October in a meadow doesn’t give you very much to identify, but goldenrod (Solidago spp.) and Indian grass (S. nutans) were plentiful among a few baby asters, Galium spp. (aka ‘Cleavers’ or ‘Bedstraw’), wild strawberry (Fragaria virginiana),clumps of unidentifiable grass and moss. I measured heights of stems and area covered, took the percent coverage to determine how much each species covered the plot,and took several picture views for record. After returning to campus, I created a hand-drawn schematic of the plot.
A few weeks later, I returned to the same plot. Apparently my methods of counting and direction are spot-on because my last step landed on a pen I had dropped on that rainy day a few weeks earlier! If you’ve ever done field work, you understand how amazing it is that I found a PEN in the middle of a meadow over 2 meters high! This time I was there to measure the ability of the meadow to hold a load. I admit, I didn’t think the stems would hold up… being so late in the year and being dried out. As usual, though, plants are amazing and surprised me yet again!
I decided to test the load by creating a 1m x 1m foam board that was sturdy, yet lightweight. I placed the board directly over the plot, placing flags on each corner. The flags allowed for a visual cue to observe movement of bot
h plants and the board, as well as giving a reference point at which to measure the height of the board after each addition of weight. After the foam board was placed on top of the plants, I measured the height at each corner (flag) for the “initial” height. I added one heavy book and measured the height at each corner. Subsequently, I added increasing weight and measured the heights. At 3 books (6.7kg), the system (the meadow plot) could no longer hold the weight. Because this was the same plants were used over the entire experiment, I believe more weight can be held by the plants in true form.
So how does this happen? Plants are amazing. In the meadow, plants grow up to 10 feet below ground (roots) and above ground. You can imagine how secure this makes these cantilever beams! Here, the Indian grass and Goldenrod grew 1.5m to 2.5m above ground. The stems reached diameters of 2-5mm. You may wonder how the stems did not break when the weight was added. Galileo was the first to record these observations, noting that bending is resisted in the outer layers, not the inner stem as some might think. Several studies have investigated this design, including F.O. Bower (1930) who compared plant stems to concrete, saying, “Ordinary herbaceous plants are constructed on the same principle. The sclerotic strands correspond to the metal straps, the surroundin
g parenchyma with its turgescent cells corresponds mechanically to the concrete.” Equisetum (Horsetail) is another champion plant for many reasons, but here, in this context, it’s a biomechanic superstar. “The hollow stem of Equisetum giganteum owes its mechanical stability to an outer ring of strengthening tissue, which provides stiffness and strength in the longitudinal direction, but also to an inner lining of turgid parenchyma, which lends resistance to local buckling. With a height >2.5 m isolated stems are mechanically unstable. However, in dense stands individual stems support each other by interlacing with their side branches, the typical growth habit of semi-self-supporters.” (Spatz, Kohler, Speck 1998). Again, plants are amazing.
After doing some mathematical calculations (very much estimated
in this case because of the imprecise nature of this ‘experiment’), it is expected that a single Goldenrod stem can support >118% of its biomass! Now, we’re not talking about the strength of steel or lead, but we can see that plants offer us new possibilities when we are designing or constructing new things! Imagine a support feature that is hollow inside and allows for storage in the “stem” as well has having the strength to support weight. Think on a smaller scale: imagine a space in which a stiff, lightweight outer covering is needed to secure something. Imagine the many possibilities that plants offer us to grow using Life’s Principles.
Over the course of hundreds of millions of years our forest has evolved to become an intricate design of function and self-support. After researching anything and everything of plant evolution this week, I have become even more in love with these photosynthetic critters. There is much biomimicry to be learned from plants: urban design, architecture, engineering, and cooperation among individuals. Now, let’s talk plants!
First, the importance of community: herbaceous, shrub, and canopy levels are put in place to create a sustainable environment for each individual and the community as a whole. (For the sake of clarity, herbaceous layers are typically knee-high and below, shrub layers are knee high to five meters, and canopy layers are anything above five meters). Within each layer, there are different sizes, shapes, and colors that allow efficient flow of resources.
The colors of plants hamper the effects of sunlight, dependent on location of the plant. Dark leaves absorb more light than light-colored leaves. Consider the dark needles of the conifer. Known to be in areas where sunlight can be limited, the dark needles allow them to take full advantage of any sunlight they receive. The cactus, on the other hand, has no shortage of sunlight in the open desert. Typically light-colored, cactus stems reflect light, preventing them from scorching in the direct sunlight. Leaf size and shape differ among species, as well. Leaves with a higher surface area are directly related to increased cooling effects. Surface area is increased by features like prickles and hairs: cactus spines, roughness of an Ulmus leaf. Research has indicated that in urban shaded areas, there is an air temperature decrease of up to 2.5℃ and a surface-soil temperature decrease of up to 8℃ (1). Leaf and plant shapes are important in much the same way as color. Larger leaves are designed to absorb more light, but what is particularly interesting to this midwestern girl is the efficient shape of the cactus. The star shape, specifically, is linked to a more energy-efficient building design in architecture. There is less surface area to receive sunlight, this buildings require less air conditioning (less energy) to cool the building.
Biomimicry is using the plant communities for inspiration. Designing urban areas with community structure in mind seems to be on the mind of some city planners. In a forest, every ‘layer’ is utilized for the benefit of both the individual and the community as a whole. Waste is reduced because there is no waste. Every material is used in some way. This is just the structural level of urban design. There is a much deeper level that is being inspired by plant communities. The ecosystem services that they offer abound. Treehugger.com quotes Janine Benyus herself as saying, “The city would provide the same level of services as the forest next door.” In the interview, she also describes the ability of a city to “build fertile soil, filter air, clean water, sequester carbon, cool the surrounding temperature, provide biodiversity and produce food.” By city planners, engineers, and architects designing infrastructure in the same way and having a conscious use of materials, we may be able to reduce energy costs and limit heat islands. The prospect of inner cities being as aesthetically pleasing as a forest is an added bonus!
We’ve done much damage to our planet. We’ve cut down trees. We’ve used pesticide and fertilizer chemicals on our soil and plants. The good news is this: the planet was designed to heal itself. To first begin, we need to help. I believe we can use bioremediation to fix some of the environmental problems we have created and as a preventative mediation for future issues. Continue reading