Apart from the tree ecology, which pyramid is always upright?

The correct answer is: Pyramid of Energy

Pyramid of energy is the only pyramid that can never be inverted and is always upright.
Pyramid of energy is always upright, can never be inverted, because when energy flows from aparticular trophic level to the next trophic level, some energy is always lost as heat at each step.
The energy pyramid is always upright because energy is constantly lost as heat when it travels from one trophic level to the next. This heat escapes into the atmosphere and is never returned to the sun.