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Temperature variations are most extreme at the surface of the soil and these variations are transferred to sub surface layers but at reduced rates as depth increases. Additionally there is a time delay as to when maximum and minimum temperatures are achieved at increasing soil depth (sometimes referred to as thermal lag).
Soil temperature depends on the ratio of the energy absorbed to that lost. [68] Soil has a mean annual temperature from -10 to 26 °C according to biomes. [69] Soil temperature regulates seed germination, [70] breaking of seed dormancy, [71] [72] plant and root growth [73] and the availability of nutrients. [74]
The reduction of weathering rate with thickening of soil is related to the exponential decrease of temperature amplitude with increasing depth below the soil surface, and also the exponential decrease in average water penetration (for freely-drained soils). Parameters P 0 and k are related to the climate and type of parent material.
The soil production rate due to weathering is approximately 1/10 mm per year. [5] New soils can also deepen from dust deposition. Gradually soil is able to support higher forms of plants and animals, starting with pioneer species and proceeding along ecological succession to more complex plant and animal communities. [6]
Growing degrees (GDs) is defined as the number of temperature degrees above a certain threshold base temperature, which varies among crop species. The base temperature is that temperature below which plant growth is zero. GDs are calculated each day as maximum temperature plus the minimum temperature divided by 2, minus the base temperature.
Temperature, soil moisture and topography are the major factors affecting the accumulation of organic matter in soils. Organic matter tends to accumulate under wet or cold conditions where decomposer activity is impeded by low temperature [ 179 ] or excess moisture which results in anaerobic conditions. [ 180 ]
In physical chemistry, the Arrhenius equation is a formula for the temperature dependence of reaction rates.The equation was proposed by Svante Arrhenius in 1889, based on the work of Dutch chemist Jacobus Henricus van 't Hoff who had noted in 1884 that the van 't Hoff equation for the temperature dependence of equilibrium constants suggests such a formula for the rates of both forward and ...
The red dotted-to-solid line depicts the average temperature profile with depth of soil in a permafrost region. The trumpet-shaped lines at the top show seasonal maximum and minimum temperatures in the "active layer", which commences at the depth where the maximum annual temperature intersects 0 °C. The active layer is seasonally frozen.