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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).
The cryic temperature regime distinguishes some higher-level groups. These regimes are based on the mean annual soil temperature (MAST), mean summer temperature, and the difference between mean summer and winter temperatures all at a soil depth of 50 cm. It is normally assumed that the MAST (in °C) equals the sum of the mean annual air ...
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 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.
Forecast temperatures will be 25-30 degrees below average for this time of year. Map shows forecast high temperatures and wind chills for Monday, Jan. 20, 2025. / Credit: CBS News.
The frost line—also known as frost depth or freezing depth—is most commonly the depth to which the groundwater in soil is expected to freeze. The frost depth depends on the climatic conditions of an area, the heat transfer properties of the soil and adjacent materials, and on nearby heat sources.
The soil moisture control section becomes udic if the mean soil temperature is lower than 22 °C and the mean summer and winter soil temperatures (at a depth of 50 cm from the soil surface) differ by 6 °C or more, is dry in all parts for less than 45 consecutives days in the 4 months following the summer solstice. Soils that have an udic ...
Soil aeration maintains oxygen levels in the plants' root zone, needed for microbial and root respiration, and important to plant growth.Additionally, oxygen levels regulate soil temperatures and play a role in some chemical processes that support the oxidation of elements like Mn 2+ and Fe 2+ that can be toxic.