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Soil respiration refers to the production of carbon dioxide when soil organisms respire. This includes respiration of plant roots, the rhizosphere, microbes and fauna.. Soil respiration is a key ecosystem process that releases carbon from the soil in the form of CO 2.
Diffusion of soil air with the atmosphere causes the preferential replacement of soil gases with atmospheric air. [5] More significantly, moreover, variation in soil gas composition due to seasonal, or even daily, temperature and/or moisture change can influence the rate of soil respiration. [7] According to the USDA, soil respiration refers to ...
The Unified Soil Classification System (USCS) is a soil classification system used in engineering and geology to describe the texture and grain size of a soil. The classification system can be applied to most unconsolidated materials, and is represented by a two-letter symbol. Each letter is described below (with the exception of Pt):
About 1,000 soil subgroups are defined in the United States. [6] A soil family category is a group of soils within a subgroup and describes the physical and chemical properties which affect the response of soil to agricultural management and engineering applications. The principal characteristics used to differentiate soil families include ...
Soil texture triangle showing the USDA classification system based on grain size Map of global soil regions from the USDA. For soil resources, experience has shown that a natural system approach to classification, i.e. grouping soils by their intrinsic property (soil morphology), behaviour, or genesis, results in classes that can be interpreted for many diverse uses.
Air is vital for respiration in soil organisms and in plant growth. [13] Both wind and atmospheric pressure play critical roles in soil aeration. [14] In addition, convection and diffusion also influence the rates of soil aeration [13] Soil structure refers to the size, shape and arrangement of solid particles in soil.
Soil respiration, the process of soil naturally releasing carbon dioxide into the atmosphere, acts as an example of this. In areas where soil moisture is not limiting (with moisture being a key part of the respiration process), soil respiration increases with rising temperatures; thus, respiration patterns form the gradient, and higher ...
Carbon can be produced in stars at least as massive as the Sun by fusion of three helium-4 nuclei: 4 He + 4 He + 4 He --> 12 C. This is the triple alpha process.In stars as massive as the Sun, carbon-12 is also converted to carbon-13 and then onto nitrogen-14 by fusion with protons.