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Why the oak circle?

By on July 1, 2015 in News

Why the oak circle?

Oak CircleAnyone that has been out to see our oak plantings on the Ojai Meadows Preserve and the Ventura River Preserve may have noticed a familiar planting pattern; that circular zone  planted with oaks and shrubs.  We call them oak nodes, or oak circles. We’ve had a few questions on the theory behind these, so here is the brief logic behind the planting method.  It is helpful to start with the goal of each node (or circle). The goal of each oak node is to one-day result in the establishment of 1 oak tree.  Because the end goal is rather modest, the nodes do not have to be large. The average size of the circle is roughly 15 feet in diameter. The only magic of that number is that it is about the throw-distance of the average lawn sprinkler. These nodes are irrigated with a single standard lawn sprinkler.  We do not want to move the sprinklers often because this is less efficient than having fixed sprinklers that can all be activated with a single valve and left for the desired amount of time for a uniform watering. So, the size is geared toward the efficiency in maintenance.

IMG_1749The next interesting aspect is the contents. Each oak node is planted with three oak trees and 5-6 companion shrubs. We plant three oaks for every one we expect to survive because oaks have naturally low success rates. Their main challenge on our preserves are the hungry gophers. While gophers can be a pain to anyone trying to grow plants, they do provide some valuable ecological services underground, so we do not suppress them on the preserves. Our main gopher strategy is called “plant enough to share.” Rather than wait until a tree dies to replace it, we just plant three in the beginning because at that time we are mobilized for planting and the trees can be installed more efficiently in numbers. Also, this results in all the trees being in the ground longer, so if two of the three die, the third has been in for the same amount of time and has progressed toward full establishment. The hardest time for an oak is the first year, so rather than have 2 or more “first-years,” we just have one. Again, efficiency.

The companion shrubs are important to the long-term success and vigor of oak trees. Oaks are known to grow at faster rates when they are combined with plant species that are common in their chosen plant community. Oftentimes, these plants may share associations of soil fungi that create a soil biota more conducive to plant growth. The shrubs also protect the young trees from excessive sun and browse by wildlife.  The shrubs also suppress weeds that threaten the oaks, and once the shrubs reach a certain size, it is no longer necessary to weed around the oaks.  Most of the cost of restoration is in weed management, so if the shrubs can reduce weeding labor, the project is more economical. Most of the oak circles are also mulched to retain soil moisture and prevent weeds as well. The oak nodes are maintained manually until the shrubs suppress weeds, while the areas between them can be managed mechanically for grasses and wildflowers.

When considered all together, the oak circle is a discreet micro-habitat/plant community node that is designed for efficient installation and management, project economy, and to anticipate and remediate for oak mortality.  Site visitors may also note some variety in their density. This is because some fields are being planted to create oak savanna habitat (10 trees/acre) while other fields are being planted to create oak woodlands (25 trees per/acre).  The different densities attract different wildlife. We try to locate them in random patterns so the resulting single oaks do not look like they are planted in rows. It’s funny, but this is harder than it seems.  From any one perspective, at least two nodes will line up, and the density results in enough trees that any line sighted through two nodes is likely to hit a third. The only way to really see the randomness is from the air. This is why we take some of our monitoring photos with a drone. From the air, the project always look less linear.

Well, there you have it. The Ojai Valley Land Conservancy oak circle.

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