User:Auwikiza/sandbox

Pedon : A pedon consists of a small volume of soil which includes the full solum and the upper part of the unconsolidated parent material (or a volume of comparable size if horizons are faint), is usually less than 2 meters in depth, and between 1 and 10 square meters in size. The smallest of these lateral dimensions is proposed for use in most soils. Pedon : the smallest body of one kind of soil, large enough to represent the nature and arrangement of horizons and soil properties to be preserved in samples. Hence, it is a volume of soil of variable dimension, (commonly 100 × 100 × 100 cm), representing a soil type. OL, HF horizons (litter at the beginning of the process of biodegradation, respectively in aerated and submerged conditions), and the R layer (unaltered rock) are sometimes considered original components and not “generated soil”, i.e. not real “soil”. Pedon : a prism of soil of variable dimension (commonly 1 × 1 × 1 m in Europe), representing a soil in a given land. Generally, the pedon is placed in the middle of a site homogeneous in terms of vegetation, parent material and relief, or homogeneous at the ground surface, hoping the best for what cannot be seen below. A pedon may be subdivided into three parts : Humipedon, Copedon and Lithopedon. The top part of the soil (Humipedon) is directly in contact with the external aerial world (aboveground plant parts and animals) while the bottom part of the soil (Lithopedon) is directly in contact with the internal mineral world; in the middle (Copedon), biological and mineral parts are interacting. The processes going on in each part are so specific that their understanding is a matter of specialists: biologists for the top, geologists or geomorphologists for the bottom and soil scientists for the middle and the whole. Soil and ecosystem coevolution was initiated during the Devonian era, approximately 350 million years ago

Soil profile : a side of the prism previously occupied in the soil by the pedon.

Humipedon : the upper part of a pedon made of organic and/or organic-mineral horizons.

Humus horizon : an organic or organic-mineral layer of the humipedon. Soil constituents are biologically organized into visibly, chemically, and/or physically distinct layers. Characterized by detectable by the naked eyes vertical discontinuities, the layers placed in the humipedon are referred as humus horizons.

Humus profile : the upper part of a soil profile, comprising organic and organic-mineral humus horizons.

Humus diagnostic horizon : a coded description of average organic or organic-mineral horizons.

Humus form   : a theoretical group of humus profiles displaying the same series of diagnostic horizons.

Humus system : a theoretical group of humus forms sharing biological/functional properties. The humus form is a specific “form = aspect” of a humus profile within a given humus system. It corresponds to the part of the topsoil that is strongly influenced by organic matter and coincides with the sequence of organic (called "O" horizons: > 20% of Organic Carbon) and underlying organic-mineral horizons (called "A" horizons, the first "agronomic" soil horizon; even in present days, classical soil scientists do not like to call "soil" the organic part of it; they accept to call it "Histosol", literally fabric, tissue soil, only in submerged condition where the biodegradation is stopped by lack of oxygen). Each humus system (type of process of biodegradation and consequent implementation of the litter transformation in a soil profile) is composed of 3–4 variations, called humus forms, ensuring the gradual transition to other humus systems.