Reddit reviews Tending Fire: Coping With America's Wildland Fires

Decades of suppression have led to the build-up of large amounts of forest debris. Additional problems include a massive increase in the density of trees per acre; from this paper:

>For example, more than 50 times more ponderosa pine trees currently occur in old-growth forests of the Gus Pearson Natural Area in northern Arizona than occurred in 1876 at the time of settlement (Mast et al. 1999).

This has several effects if you don't allow small ground fires to occur:

1. You don't kill off young trees. Too many survive; tree density increases.
   
   
2. Too many trees = not enough water. Without water to produce sap, bark beetles go nuts. Trees start dying- even more fuel.
   
   
3. Ground fuels build up. This leads to larger fires, and ladder fuels that bring fires into the canopy- remember, the trees are already dry to begin with, a function of drought, and of trees that are at too high a density for what little precipitation there is.
   
   
4. Once debris on the ground builds up to some critical level, tree roots start growing up and out of the mineral soil. Wildfires that moonscape the terrain, outright killing small trees, spare the large ones- but the old trees succumb to fire later on, as the ground fires kill the roots that have grown upward into the debris that is scorched off.
   
   Of course, the blame lies in decades of fire suppression- a function of "oh the poor wild animals" (which have adapted to routine, small ground fires in a spectacular fashion- but not the huge crown fires of much death that have resulted), and of industry and commerce protecting their interests (relatively high tree density).
   
   This book has interesting insights if you care for them. I would elaborate upon any of the points I've made or any questions you might have. It's a very complicated subject that isn't well suited to terse answers.