Abstract: The forests of cultivated Mongolian pines (Pinus sylvestris var. mongolica) in the sand lands of the Zhanggutai region are stands of high productivity of biomass, their growth depends mainly on the location of the sand dunes on which they grow and the type of forest cultivated. A great deal of nutrient elements are stored up in the tree layers and accumulated in the litters of such forests, the upper layer of soil under which is rich in humus, N and P and the content of which decrease gradually with the depth of soil. The biomass, the humus content and the components of the humic acid of the forest soil can be greatly increased and improved if Mongolian pines grow in cooporated with Populus pseudo-simonii to be a mixture forest.