Geography of soil formation, how soils are formed

Soil is the product of a combination of five factors: rock, climate, biology, topography and time. Introduction: Soil is composed of minerals weathered from rocks, animals and plants, organic matter produced by the decomposition of microbial residues, soil organisms, moisture, air, oxidized humus, etc.

Solid matter includes soil minerals, organic matter and nutrients obtained by microorganisms through light sterilization. Liquid matter mainly refers to soil moisture.

The soil parent material is formed under certain hydrothermal conditions and biological action, and through a series of physical, chemical and biochemical processes.

Frequent material and energy exchange and transformation between the parent layer and the environment have occurred to form soil humus and clay minerals, and a layered soil profile has been developed, and fertile soil has also emerged.

Soil is the product of the comprehensive action of five natural factors: parent material, climate, biology, topography and time. All soil-forming factors always exist at the same time and are equally important and irreplaceable in the process of soil formation.

The formation of the soil is over-aged

Weathering breaks the rock, changes the physical and chemical properties, and forms a loosely weathered crust, the upper part of which can be called the soil parent material. If the weathered crust remains in place and forms a residue, it is called residual parent material.

If the weathered material is migrated under the action of gravity, flowing water, wind, glacier, etc., to form colluvium, alluvium, marine deposit, lacustrine deposit, moraine and aeolian deposit, etc., it is called the sedimentary parent material.

Suitable sunlight and humidity conditions on the rock surface breed mosses, which rely on trace rock minerals dissolved in rainwater to grow, and produce large amounts of secretions to chemically and biologically weatherize the rocks.

With the multiplication of bryophytes, the interaction between organisms and rocks is increasingly strengthened, and soil is slowly formed on the surface of rocks. Since then, some higher plants have gradually developed on the young soil, forming a clear differentiation of the soil.

Soil Formation Rules:

From the perspective of the material cycle of the earth system, the occurrence and development of soil fertility is the result of the interaction between the geological cycle of natural materials and the small cycle of organisms. The geological cycle refers to the process by which mineral nutrients cycle between land and sea.

The weathering products produced by weathering on land rocks are finally deposited in low-lying lakes and oceans through leaching, denudation and transportation by various external forces, and various sedimentary rocks are formed through consolidation and diagenesis. After a long geological time, the sedimentary rocks of these lakes and oceans have been uplifted again into terrestrial rocks with crustal movements, and have been weathered again.

The cycle of this material cycle is about 106 108 years. Among them, the weathering process of rocks and the leaching process of weathering products are most closely related to soil formation.

The influence of topography on soil formation is mainly through the redistribution of matter and energy, and the indirect effect of land on soil is indirect. In mountainous areas, different climate and vegetation zones are formed due to the vertical changes of temperature, precipitation and humidity with the increase of terrain, resulting in significant vertical zone differentiation of soil composition and physical and chemical properties. The study of soil characteristics in the mountainous areas of the southwestern United States showed that soil organic matter content, total porosity and water holding capacity increased with altitude, while pH decreased with altitude.

In addition, slope and aspect, which can affect soil development, can change water, heat and vegetation conditions. On steep slopes, it is difficult to develop into deep soils because gravity and the erosive force of surface runoff tend to accelerate the migration of loose surface materials. However, in the flat terrain, the erosion rate of loose material on the surface is slower, so that the parent material can gradually develop into deep soil under more stable climatic and biological conditions. Because the sunny slope receives more solar radiation than the shady slope, the temperature condition is better than that of the shady slope, but the moisture condition is worse than that of the shady slope, and the vegetation coverage is generally lower than the sunny slope, which leads to the difference of physical, chemical and biological processes in the soil.