The fertility of soils under a forest is mainly sustained by nutrient recycling. When trees and other plants in the forest shed their leaves, branches, and other organic matter, it decomposes and enriches the soil with nutrients. The decomposed organic matter also helps to retain moisture in the soil, which is important for the growth of plants. Additionally, the roots of trees and other plants help to stabilize the soil and prevent erosion. While rodent activities and the protection of the soil from direct rays of the sun and raindrops can also contribute to soil fertility in some ways, nutrient recycling is the primary factor that sustains the fertility of soils under a forest.