What physical attributes of atmosphere and flora could cause clouds to form on a regular basis below the canopy of a forest between one-fourth and one-half the height of the forest, without impacting the global norm of high-altitude clouds (at thousands of feet)?
Assume a non-Earth environment for answers to this question; specifically, an atmosphere as described in this question. If the ground composition is a factor, I have in mind a dense weave of roots a few dozen feet thick floating atop a deep ocean. The foundational plants in this composition are moss- or algae-like and extend out from a continent as a biological extension to the land area. The roots collect particles and corpses which allows for the growth of the forest.