For the most part, tanks fight at distances in the hundred if noth thousands of yards, not really practical in a dio. The trouble with explosions (and fire and smoke) is they are ephemeral, lasting only fragments of a second and leave a lot of stuff suspended in the air.the expansio of gases/shockwave also affects things around them in specific manners, bending and more breaking/suspended stuff. In the 27 years I've been attending shows, judging and hanging out on line, I can count only a few really effective action dioramas, and none of them attempted actual explosions.
About the only way you might do this effectively would be by creating a boxed diorama where you control the lighting and directio of view. That would allow you to implant an LED into the explosion and support the upper part of the tree.
Here are a couple pictures of explossive type action that were on display at World Expo in 2005: