The metaphysics of elemental ethnicity

Pictured above, left to right: Young adult humans who are have highly dominant air, earth, fire, and water traits.

Elemental Variants among Humans

Humans are all over the map with a modest tendency towards earthy traits because most of their societies are very agrarian.
Humans and the other Third Age mortal races are more susceptable to generational change than most other. The Scarterran heriditary norm is that children receive 45% of the mother's traits, 45% of their fathers traits, and 10% of their ambient environment's traits. The human norm is 40/40/20.

Elemental Variants among Dwarves

The dwarf default is primary earth traits with secondary fire traits. Dwarves are spiritually tied to the earth and have innate instincts for metal and stonework and are comfortable underground.
Meckelorn is a bit colder than other dwarf lands and the Meckelorners recently had a long exile where most of the population was mobile. Most Meckelorner dwarves have tertiary air traits. Meckelorner dwarves from long family lines of rangers have more pronounced airy traits.
Stahlheimer dwarves hew closely to the default dwarf norm but they have fairly recently expanded along the coast line and built up a growing port city and a merchant and military fleet. This is creating a small but growing minority with tertiary water traits. A very tiny number of Stahlheimers with a lot of rangers in their family line develop minor airy traits.
Mondarian dwarves are the most divergent dwarf culture on Scarterra developing for roughly a thousand years on a cluster of tropical islands. They tend to have co-dominant earthy, fiery, and watery traits.
Due to their lifestyles, gnomes are fairly earthy. Due to their birthright as children of Mera, the water goddess, gnomes are fairly watery too but this is fading slowly over the generations because few gnomes take maritime professions.

Elemental Variants among Elves

In the Second Age, elves lived almost everywhere, so they used to make up every possible combination of elemental traits, but the four elf cultures have been developing indepenently for at least 2500 years.
The wood elf norm is dominant earthy traits with secondary airy traits, but there are a lot of distinctive regional minority populations in their homeland of Codenya
The volcanic wood elf minority has noticeable fire traits and the taiga elf minority has exaggerated airy traits. There are also a few somewhat watery minority groups as well.
The different ethnic enclaves in Codenya intermarry a fair bit so it is not especially unusual to find a wood elf with at least minor cosmetic traits of all four elemental ethnicities.
Almost all grey elves live at most a hundred miles from the sea and most of them live in tropical or subtropical latitudes. The Grey elf norm co-dominant watery and fiery traits with tertiary earth traits but the territory of the Elven Empire is large enough that there are a lot of regional exceptions to the norm.
The nation of Kahdisteria is bounded by the sea to the east and a tall mountain range to the west. It is not too surprising that most Kahdisterians, better known as dark elves have co-dominant or nearly co-dominant earthy and watery traits. On the whole, more elves live in the east than the west, so watery traits win out the majority of the time. The dark elves from the northern region develop tertiary airy traits and the dark elves from the southern region develop tertiary fiery traits.
The sea elves, unsurprisingly have very dominant watery traits. Once in a while, a sea elf may develop a minor non-watery trait here and there but that is the exception, not the rule.

Elemental Variants among Gnomes

Gnomes tend to culturally assimilate with other races. Over generations, they will begin to physically assimilate as well. Meckelorner gnomes have similar elemental traits to the Meckelorner dwarves. Fumayan gnomes have similar elemental traits to Fumayan humans, and so on and so forth.
Gnomes were created by Mera who is the water goddess and most gnomes are farmers or descendants of farmters and gnomes are spiritually grounded in down-to-earth common sense, so gnomes tend to be slightly more watery and more earthy than whatever the cultural group they are attached to.

Orcs

Orcs are just as susceptable to generational elemental change as humans, so they theoretically could be a wide diverity of orc races and tribes. The vast majority of orcs live int he northern region of West Colassia and they have not successfully spread to new areas in large numbers. This means few differ substantially from the default orc which has dominant airy traits and secondary earthy traits.

Scarnoctis

Scarnoctis is underground, so logically most if not all of the subteranean races would develop strong earthy traits. While this is largely true, earthy traits are not as pronounced as one would guess.
The Elemental Plane exists in the planetry core of Scarterra/Scaraqua. This means that Scarnoctans are physically closer to the elemental plane so there is more exposure to all four elemntal forces not just th earth.
This means that subteranean races usually, but not always, have more pronounced generational and geographic variation than their above ground counterparts.
For unknown reasons, goblins seem especially prone to this change, and Scarnoctis has inadvertantly spawned hyper-elemental variants of goblins for all four classic elements, jumping goblins (air), red goblins (fire) frog goblins (water), and the rarely seen stone goblins (earth).

First Age Mortals

Any mortal race that predates the First Unmaking is much less impacted from the ambient elemental energies than those races that came after it.
To outsiders, all kobolds look alike. The kobold race has three distinctive cultural groups, but even kobolds cannot tell what group another kobold is from by sight alone. The three kobold groups act differently, dress differently, worship differently, and talk differently but biologically they are more or less the same.
Giants and delvers are in a similar boat.
Dragons vary a lot from individual to individual, but this has little if anything to do with elemental metaphysics. Dragons are inherently magical and have strong will. Dragons of course draw many traits from their mothers and fathers, but their bodies and powers will gradually grow and adapt to match their personality traits and goals which will then affect what traits they pass on to their offspring.
Beholders are also highly magical and strong willed and this causes more individual and family variations.

How this Manifests

elemental ethnicity in mortals, overview article
Air Ethnicity overview
Earth ethnicity overview
Fire ethnicity overview
Water ethnicity overview

Type

Metaphysical, Elemental