california forester here
through a combination of dendrochronology and local geological records we can get a fairly accurate idea of fire interval in any given location, as shown:
>find big old tree>count rings to determine age>see if any rings have char on them>count back to see what year fire occuredif you do this with enough trees over a landscape you can start to get a general idea of how often those trees were getting singed
in regards to your theory about the mud, most often a technique is used where you sample the mud for pollen and then date the pollen
>>2172478you can actually see very clearly the policy that the forest service had in place being amplified by the introduction of bulldozers and chainsaws around WW2. the USFS wanted complete fire exclusion as they saw it as a preventable and undesirable trait of the forest, and did everything in their power to prevent wildfires from happening. Due to this, ~100 years of additional fuel has built up in the forests, causing any small fire to balloon into a raging inferno incredibly quickly. The fires of the early 1900's-1940's were pretty much on track with the standard up to that point, the difference being they were mostly light intensity over a large uninhabited area, rather than an extremely high intensity over a small inhabited area
