'piso térmico'
we know that it refers to segments ov territory over sea level
2 Answers
Hola:
It refers to the different altitudes in mountains and how with each "piso térmico" there are different flora, fauna and habitats.
Good luck.
I would interpret this as "thermal layer".It probably corresponds to depth of ocean currents.
Context is always important in any interpretation. You will get more responses if you explain where you are reading this term. Welcome to the forum.