Crystal Heart and TOH how do they relate?

[Nature's Spell 526]

I've been thinking of Cadence a lot and how her element, the Crystal Heart, fits in with the Tree of Harmony. In the case of Twilight the TOH is literally her Cute Mark and it also shows Luna and Celesta's Cute Mark. Makes sense since the three were all barers of the EOH. Cadence's Cute Mark is the Crystsl Heart, which may also be the source of her power, since her CM is not shown on the TOH. The implication is that the Crystal Heart and Tree of Harmony are equals, although you'd think that love could also be an Element. It makes Cadence uniquely powerful and importan; the most recent in a line of Princesses of Love. As a character who isn't always liked it gives her a boost. I guess Equestria is governed by the Sun, Moon, Friendship and Love. Are we missing anything?

Edited December 6, 2014 by Nature's Spell