What is the leaf mold ? What are you referring to for JMS. You have mention from the forest, is it just leaves, or can it be rotted wood or any thing that is turning into humus. I live in zone 9 and it’s not humid like in the north and leaf mold does not happen here since it’s so hot and not enough moister. The soil takes up the nutrients faster then norther cold climate. If you are referring to humus then they are categorized in different type of decomposition. You also mentioned leaf mold soil , are you referring to decomposed matter with soil so mull “humus “. Or are you refering to mineral(AH) horizons, which is less then 30% organic matter.
Mor humus: undecomposed and not mixed with soil.
Moder humus: undecomposed and partly decomposed with soil
Mull humus: we’ll decomposed with soil
Muck humus: highly decomposed