Folks,
In real world scenarios, fixed ELT will fail to transmit a usable signal on better than (worse than) 95% of occasions.
Fundamentally, fixed ELT are a waste of money, and all they produce is a false sense of security.
So, Muralidharan, the most likely reason has nothing to do with a forest, beyond the fact that crashing in a forest will produce a greater than "normal" likelihood that the ELT aerial will be damaged, a greater threat by far, than any masking by the local conditions.
Tootle pip!!