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Soil is a mixture of organic matter, mineral matter, gas, liquid and organic matter, supporting life together. The earth's soil is called the ecosystem, which has four important functions:
Geosphere is connected with lithosphere, hydrosphere, atmosphere and biosphere. The term pedolith is often used to refer to soil, which is transformed into ground stone in the sense of "foundation stone". Soil is composed of solid phase (soil matrix) of mineral and organic matter and porous phase containing gas (soil atmosphere) and water (soil solution). Therefore, soil scientists can think of soil as a three-state system of solid, liquid and gas.
Soil is the product of many factors: climate, topography (elevation, direction and slope of terrain), biological and soil parent materials (original minerals) interact with time. It develops through many physical, chemical and biological processes, including weathering and associated erosion. In view of its complexity and strong internal connection, soil ecologists regard soil as an ecosystem.
The dry bulk density of most soils (considering soil density for dry weight) is between 1.1 and 1.6 g / cm3, while the density of soil particles is much higher, between 2.6 and 2.7 g / cm3. Although fossil soil can be preserved to the earliest Archean age, there is almost no soil on the earth that is older than Pleistocene or Cenozoic.
There are two basic branches of Soil Science: Pedagogy and pedagogy. Morphology studies the effects of soil on organisms. Pedagogy focuses on the formation, description and classification of soil in the natural environment. In engineering terms, soil is included in generalized plaster, which also includes other loose material above bedrock, such as the moon and other celestial bodies. Soil is often referred to as soil. Some scientific definitions distinguish soil from soil by limiting the former term specifically to the replaced soil.
Soil is the main component of the earth ecosystem. From ozone depletion and global warming to rainforest destruction and water pollution, processes in the soil affect the world's ecosystems in a profound way. As far as the carbon cycle of the earth is concerned, soil is an important carbon pool, which may be the most sensitive to human interference and climate change. With global warming, it is predicted that soil will add carbon dioxide to the atmosphere due to the increase of biological activity under high temperature, which is a positive feedback (amplification). However, this prediction has been questioned by the latest understanding of soil carbon turnover.
Soil can be used as engineering medium, habitat of soil organisms, nutrient and organic waste recovery system, water quality regulator, atmosphere component regulator and plant growth medium, so that it becomes a vital provider of ecosystem services. Because soil has a large number of available niches and habitats, it contains most of the genetic diversity of the earth. A gram of soil can contain billions of organisms, belonging to thousands of species, most of which are microorganisms, and are largely untapped. The average prokaryote density of the soil is about 108 organisms per gram, while that of the ocean is less than 107 per ml of seawater. The organic carbon retained in the soil eventually returns to the atmosphere through the process of heterotrophic respiration, but a large part of it is retained in the form of soil organic matter. Cultivation usually increases the soil respiration rate and leads to the consumption of soil organic matter. Because roots need oxygen, ventilation is an important feature of soil. This ventilation can be achieved through an interconnected network of soil pores that also absorbs and retains rainwater, making it easily absorbed by plants. Because plants need nearly continuous water supply, but there will be sporadic rainfall in most areas, so the water holding capacity of soil is very important for the survival of plants.
Soil can effectively remove impurities, kill pathogens and degrade pollutants. The latter property is called natural attenuation. Generally, the soil maintains a net absorption of oxygen and methane and undergoes a net release of carbon dioxide and nitrous oxide. Soil provides physical support for plants, air, water, moderate temperature, nutrients and protection from toxins. By transforming dead organic matter into various forms of nutrition, soil provides plants and animals with easily accessible nutrients.
