A California hillside during the dormant season.
What are the trees adding to the landscape to produce the circle of green grass? Mycorrhizal colonization? Shade?
When you look at the outlines closely, the patterns all move to the downhill side. There does not seem to be a correlation to sunlight direction.
I suspect the trees are capturing water from the atmosphere and transferring it to the soil. Increased soil moisture is the only thing I can think of that would move downslope consistently.
What do you think is happening here?