It seems you're asking why montane forest trees have leaves. The answer is actually quite simple:

All trees need leaves for photosynthesis. This process is how trees convert sunlight, water, and carbon dioxide into energy to grow and survive.

Montane forests, which are forests found at higher elevations, are no exception. While these forests experience colder temperatures and often have shorter growing seasons, they still need leaves to function. The leaves of montane forest trees might be:

* Smaller and thicker to conserve water and withstand harsher conditions.

* More needle-like (like pines and firs) to reduce water loss and shed snow more easily.

* Deciduous (like maples and oaks) in areas with cold winters, allowing the trees to conserve energy by dropping their leaves.

So, the presence of leaves on montane forest trees is a necessity for their survival, just as it is for trees in any other forest type.