An experiment in tree planting

Can you figure out the hypothesis being tested?  And see the result?  Answer below the fold.

Back in 1973 scientists began a project in ‘experimental forestry,’ with the aim of learning about the spacing of trees and its effect on growth. They planted circles of cedars near Nichinan City in Miyazaki Prefecture, with smaller inner circles expanding incrementally into larger radiuses to create 10 perfect rings.

As you can see in the photo below, the experiment seems to show clear results. The concave shape suggests that the outer circles of least density promote a higher growth, with the tree size getting steadily smaller as the density increases.

More space equals less competition for resources such as water and sunlight, so it’s easier for these outer trees to grow bigger and stronger while those on the inside fight it out amongst themselves.

According to a document from Japan’s Ministry of Agriculture, Forestry and Fisheries, the eventual height difference between the smallest trees at the center and the tallest trees on the outer ring was over 5 meters.

Via Reddit.