The study looked at how different types of trees grow in compact urban soils. They found that pitch pine, Austrian pine, and Norway spruce can grow in dense soils if they have enough water. Pitch pine was the best at growing in these conditions. A very dense silt loam soil made it harder for all three tree species to grow, but a sandy loam soil did not. The roots of the trees had trouble growing in denser soils, especially in the silt loam. The researchers suggest that measuring soil resistance to penetration is a better way to predict how well tree seedlings will grow than just looking at soil density.