Fridays are amazing. Really. It’s the one day of week I only have one class, even if it is three hours long. Every so often, I have to remind myself why in the world I just had to sign up for 6 classes. On the other hand though, I wouldn’t drop any of them even if I had the chance. This morning for Plants, we spent the morning walking around the downtown area and taking a close look at the choices the landscape architects had to make in urban conditions. We made interesting comparisons between the downtown and its street trees, and the nearby upland woodland on Skinner’s Butte.
I was especially surprised to learn that most city trees have a lifespan of only 7 years after they’ve been planted, due to pollution, wind-tunnel effects from surrounding buildings, and compacted or poorly aerated soils.
It’s amazing how much these life spans could be extended by following basic principles of what trees need to grow. First of all, they need to have enough soil space. A good rule of thumb for tree wells is considered 70 square feet or larger. That may seem like a lot, but if this space can be covered with well grates, not only can people have a wider sidewalk, but the tree is also protected from compacted soils like the ones created by high traffic above the roots. Trees also need air in the soil, something that can’t happen if we put sidewalks and roads right over the root space. It’s obvious if a tree is lacking air around its roots, because the roots will grow close to the surface and be more likely to break apart sidewalks and roads.
In urban situations it is extremely important that a single species be no more than 5% of the total planting in the area. This avoids the quick spreading of diseases and ensures that there will be a variety of ages and sizes of trees.
As designers, we have the opportunity to influence what people consider to be beautiful by increasing their exposure to things like native plants, wetland plantings in storm water beds, and variety in street trees. By introducing them in urban contexts, even if they don’t provide habitats for wildlife, including bees, butterflies and birds, citizens will be more likely to take these concepts into their yards, where wildlife is more likely to thrive.
One of our assignments for Plants is to map a natural riparian area in the Willamette Valley as a group of three, so after class, Anna, Daniel and I hit the trails along the river to find a space with a wide variety of forest floor, understory, and canopy species. Then we spent and hour and a half figuring out the best way to plot out the trees on our plan, and identifying them. Our site ended up having a lot of Incense Cedars, but we managed to find a Bigleaf Maple, an Oregon Ash, lots of Osoberry and Snowberry, and some English Ivy. The total area mapped was about 3,600 square feet.
After taking a lunch break around 2, I hit the rec center for a 50 minute swim workout, followed by an ab workout and a double round of circuit training. Now I’m about to head out with my roommates to see the new Zach Galifianakis movie.