The study looked at different ways to help black spruce trees grow better in Minnesota forests. They tested six methods like cutting trees in strips or patches, thinning, and leaving some trees for shelter. After 10 years, they found that a model using treatment, compartment, and plot as random effects worked best for predicting tree growth. This model was better than the usual model used in the area. By using this new approach, they could predict tree growth more accurately for both small and large trees.