design formative element dictionary content, goals, editing suggestions

[dylanbeaudette]

Sub-Issues:

• possibly normalize dictionaries such that each term is tied to a master "root" (this is complicated because the same roots can be used in slightly different ways across levels of ST)
• add "root" column to existing dictionaries for iteration vs. assumption that "connotation" is replicated

[brownag]

So, I am proposing we remove the redundancy from the formative element table. We already are partitioning meaning by the levels of ST... but indeed this is only the tip of the ice berg.

I don't know that we want to go the route of doing this for all the instances this kind of thing affects. Here is an example.

Currently we have:

sulfo,sulfur,presence of sulfides or their oxidation products,, 
sulfi,sulfur,presence of sulfides or their oxidation products,, 
sulf,sulfur,presence of sulfides or their oxidation products,,

Which produces identical results to the simplest case:

sulf,sulfur,presence of sulfides or their oxidation products,,

Now, sulf- is an example of a formative element whose meaning varies depening on the great group it is used with. There are some patterns, but they are not perfect.

sulfo- always means presence of a sulfuric horizon

sulfi- always means presence of sulfidic materials

sulfu- always means presence of a sulfuric horizon (only one instance -- sulfudepts)

sulfa- varies depending on the soil order (entisols cannot have a sulfuric horizon)

• sulfaquerts: presence of a sulfuric horizon or sulfidic materials,,
• sulfaquepts: presence of a sulfuric horizon
• sulfaquents: presence of sulfidic materials

As it stands we have a mixture of degrees of specificity of these definitions... some refer to actual existing definitions in soil taxonomy, whereas others simplify the meaning. "presence of sulfides or their oxidation products" is not wrong, with sulfur as the primary connotation, but saying either of the diagnostic materials/horizons is present will be wrong for some subset if we limit to just sulf-.

We can go and define all of instances I gave above as their own definition, and it works, or we can go the route of not actually identifying the specific relevant definitions and criteria in these more generalized explanations. I know @dylanbeaudette has discussed different levels of detail for this output, and I think the current defnitions we are using probably span what would be a couple different levels as is.

[brownag]

From Soil Taxonomy (2003), CHAPTER 6 The Categories of Soil Taxonomy, p. 119. https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_051232.pdf

I think we need to work these definitions into the ST_formative_elements metadata to explain "intragrade" "intergrade" "extragrade" logical columns. Then we should ensure that the records are assigned as "correctly" as possible.

Typic subgroups.—These are not necessarily the most extensive subgroups, nor do they necessarily represent the central concept of the great group. In some taxa typic subgroups simply represent the soils that do not have the characteristics defined for the other subgroups.

Intergrades or transitional forms to other orders, suborders, or great groups.—The properties may be the result of processes that cause one kind of soil to develop from or toward another kind of soil or otherwise to have intermediate properties between those of two or three great groups. The properties used to define the intergrades may be:

1. Horizons in addition to those definitive of the great group, including an argillic horizon that underlies a spodic horizon and a buried horizon, such as a thick layer of organic materials that is buried by a thin mineral soil; or
2. Intermittent horizons, such as those described in the section of chapter 1 that deals with the pedon; or
3. Properties of one or more other great groups that are expressed in part of the soils but are subordinate to the properties of the great group of which the subgroup is a member. One example of different depths of saturation and reduction was given earlier. Another example might be an Alfisol that has an ochric epipedon a little too thin or a little too light in color to be a mollic epipedon. This feature could result from an invasion of grassland by forest or the reverse, from the coexistence of both grass and forest, or from the erosion caused by human activities.

Extragrades.—These subgroups have some properties that are not representative of the great group but that do not indicate transitions to any other known kind of soil. One example of an overthickened mollic epipedon was given earlier. Other examples are soils that are very shallow over rock (Lithic) or soils that have high amounts of organic carbon (Humic).

[brownag]

I think some of the explanations need revision.

For instance "typic" probably should read "central theme of great group concept" (not "subgroup").

library(SoilTaxonomy)
cat(explainST('typic endoaqualfs'))
#> typic endoaqualfs
#> |     |   |  |                                                                                      
#> central theme of subgroup concept                                                                   
#>       |   |  |                                                                                      
#>       ground water table                                                                            
#>           |  |                                                                                      
#>           characteristics associated with wetness                                                   
#>              |                                                                                      
#>              soils with an argillic, kandic, or natric horizon

Also, we should consider using/replacing some the connotations included in latest versions of the Keys

e.g. "Hapl" -> "minimum horizon development" rather than "central theme of subgroup concept"

Also consider adding historical formative elements no longer used in modern versions of Taxonomy