Thinning the pine trees in a forest helps the spruce trees underneath grow better. The study looked at different levels of thinning in pine trees and how it affected the growth of spruce trees below. They found that heavier thinning in the pine trees led to faster and bigger growth in the spruce trees. Removing some of the spruce trees didn't really affect the growth of the pine trees above. Overall, having a mix of pine and spruce trees can work well, but the pine trees need to be thinned regularly to keep the spruce trees healthy and growing strong.