Noel, you are lucky to be in an area so beautiful and honestly you should include us in your collecting trips via photographs, descriptions and maybe a bit of story telling. In nature rain fed areas (forests) I have also found these plants growing mostly in leaf litter and remains of dead creatures, never in clay. Here in the mountains I have seen plants in leaf litter and in deserts, sand. As to clay or what we call soil
never exotic species grown in the garden. Mostly field crops (and that to with tilling) grow in clay or commercial trees but come to think of it, even exotic furniture wood seems to prefer leaf litter. True but not quite, Burma Teak has its roots in soil but the soil is covered with a two feet or so layer of organic litter which provides the nutrients and keeps the roots aerated. As to dry leaf litter, put your hand into the layer in peak dry season and I am quite sure you will find moisture. Plants love moisture and hate it if their roots are standing in water, then they get enough moisture from the atmosphere in the shape of dew, humidity, condensation. This organic material also draws moisture from the atmosphere. They make do and survive quite well. It is we who kill them with tender loving care and over watering. Plus the silly clay and rotting(corrosion) of roots from strong chemical fertilizers.
Also nitrite, nitrate conversion bacteria(example Citrobact) thrives in acidic medium (leaf litter).
Regards,
Masud.