Saturday, May 8, 2021

Reforestation: The Miyawaki Method

A popular new method of replanting forests that have been devastated was developed many years ago by a Japanese botanist, Akira Miyawaki (now 93 years old). This method is now being used around the world and is especially popular in the tropical parts of India.

The method is supposedly simple, but of course there are a lot of details. Nevertheless, the basic idea is very simple: plant a thick growth of seedlings of native tree species and let them thin themselves out into a diverse forest. It is the exact opposite of a tree plantation, which consists of a single tree species, each tree spaced out enough that it will probably survive. We have a lot of plantations in Oklahoma, mostly loblolly pines used by Weyerhaeuser Corporation for wood pulp, mostly along State Highway 3 on the east side of the state. Instead, the Miyawaki method is an almost exact replication of natural forest succession, except that it skips the weedy and shrubby stages, going directly to the forest stage. If you use a mixture of native species, they will not only be adapted to local conditions, but will interweave themselves into different layers and roles.

But this is not what I found the most interesting about the method. To me, the most important part was that this method allows nature itself to do the thinning-out of the trees. You know that a lot of them are going to die, but the result will be astonishing.

Plant ecologist K. Yoda found that a thick growth of plants would thin itself out as the bigger plants grew bigger and the smaller ones died. This is hardly surprising in itself. But Yoda found that in a graph in which the average plant weight is a function of density, both on logarithmic scales, the slope of the line was very close to -3/2. The confusing thing about such a graph is that the time axis goes backwards: you have to read the graph from right to left. Or is it backwards? Remember that in Japan they traditionally read right to left. This discovery, like the Miyawaki method, came out of Japan. Here is a recent article about this pattern. Yoda used monocultures (a single species) but it apparently works with polycultures as well.

My message is simple: If you want to restore nature, let nature do it, giving it just a little help.

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