Mor humus is a form of
humus
In classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Lati ...
occurring mostly in
coniferous forests
Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All extant ...
where there are few
earthworm
An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. Th ...
s and micro organisms to decompose soil organic matter.
The
evergreen
In botany, an evergreen is a plant which has foliage that remains green and functional through more than one growing season. This also pertains to plants that retain their foliage only in warm climates, and contrasts with deciduous plants, which ...
needles that litter the forest floor are slow to
decompose
Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is ...
, in part due to their chemical composition (low pH, high carbon), but also because of the generally cool temperatures and low microbial activity. Unlike other types of humus, the litter layer is substantial and well-differentiated from the
fermentation
Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...
layer, and the fermentation layer remains distinct from the humus layer. It is one of three classifications of humus (decomposed material that can no longer be identified as plant origin after undergoing the humification process.)
Characteristics
The decomposition rate is very slow in mor soils. The fermentation layer below the litter layer consists of plant remains still in varying degrees of decomposition. The humus layer of fully decomposed plant material lies beneath these two laters. In comparison, the fermentation and humus layers are not distinguishable in mull soils due to earthworm and micro organism activity that assists with rapid decomposition of organic materials.
Mor soils are usually very acidic.
[ They are usually cold, wet soils under coniferous forests. Soil ]mite
Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...
s are more common in acidic soil
Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the neg ...
s topped with mor humus than in other types of soils. Mycorrhizal
A mycorrhiza (from Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plan ...
tips per unit of volume are greater in mor soils than mull soils.
See also
* Moder humus
References
Soil
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