In mixed forests, various trees grow. Forest-forming species are both broad-leaved (maples, oak, linden, birch, hornbeam), and coniferous (pine, larch, fir, spruce). In such natural zones sod-podzolic, brown and gray forest soils are formed. They have a fairly high level of humus content, which is due to the growth of a large number of herbs in these forests. Iron and clay particles are washed out of them.
In coniferous-deciduous forests, the land of sod-podzolic type is widely formed. In forest conditions, a significant humus-accumulative horizon is formed, and the turf layer exhibits a small thickness. In the process of soil formation, ash particles and nitrogen, magnesium and calcium, iron and potassium, aluminum and hydrogen, as well as other elements, are involved. The level of fertility of such soil is not high, since the medium is oxidized. Sod-podzolic soil contains from 3 to 7% humus. It is also enriched in silica, and poor in phosphorus and nitrogen. This type of soil has a high moisture capacity.
Gray soils and burozems
Brown and gray soils are formed in forests, where coniferous and broad-leaved trees grow simultaneously. The gray type is transitional between podzolic soils and chernozems. Gray soils form in warm climates and plant diversity. This contributes to the fact that plant particles, animal excrement due to the activity of microorganisms are mixed, and a large and rich in various elements humus layer appears. It lies deeper and has a dark color. However, the soil every spring, when the snow melts, experiences significant moisture and leaching.
Brown forest soils form even in a warmer climate than forest soils. For their formation, summer should be moderately hot, and in winter there should not be a permanent snow layer. Throughout the year, humidification of the earth occurs evenly. Under such conditions, the humus becomes a brownish brown hue.
In mixed forests, you can find a variety of soil types: burozems, gray forest and sod-podzolic. The conditions for their formation are approximately the same. The presence of thick grass and forest litter contributes to the fact that the soil is enriched with humus, but increased humidity helps to wash out various elements, which somewhat reduces soil fertility.