Field Analysis:How Pores

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Soil porosity and roots
Porosity refers to visible pores or voids between sand grains, stones or soil aggregates, or created by rooting and biological activity. You should record the dominant type, overall pore frequency and the orientation of the pores (vertical/horizontal etc.).

Soil pore type
Use the pore type pictures below to help identify the dominanat pore type.
 * Tubular (single) are cylindrical, elongated pores e.g. worm channels.
 * Tubular (dendritic) are cylindrical branching voids e.g. empty root channels.
 * Vesicular/vesicles are ovoid to spherical voids e.g. trapped gas bubbles.
 * Irregular are non-connected cavities and chambers of any shape in the soil matrix.
 * Interstitial are voids between sand grains and rock fragments.
 * Crack are fissures not associated with soil structure.



Pore frequency
Frequency is determined by estimating the surface area occupied by water or air-filled voids. Use the frequency charts below to identify the most appropriate frequency class.

Pore orientation
Record whether there is a tendency overall for pores (particularly tubular or crack pores) to run:
 * Vertically down through the section.
 * Horizontally across the section.
 * Randomly at all orientations through the section.
 * Dendritic branching from a particular point or level within the section.

Roots
In buried archaeological soils and sediments it is not only fresh roots, but traces of roots that have since decayed away that are of interest. These root traces may include dendritic void patterns, root impressions on the surface of peds, and the preservation of formaer rooting patterns in iron mottle and concentration patterns.

Root sizes
Record the presence and frequency of root size classes in the deposit:
 * Fine roots less than 2 mm in diameter
 * Medium roots 2-5 mm in diameter
 * Coarse roots greater than 5 mm in diameter

Root frequency
Record the number of roots in a 10 cm x 10 cm area of soil.

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