Forest type data was created by the USFS the analysis image is part of the Google Earth Engine Community Data Catalog

Forest Type Data page:

https://gee-community-catalog.org/projects/us_ftype_fgroup/

Forest maturity data comes from the Forest Maturity Map –. a project led by Dr Dominick DellaSala, Wild Heritage. The data and references can be found at the link below:

Past fire boundaries come from the Monitoring Trends in Burn Severity (MTBS) burned area boundaries dataset produced by the US Geological Survey. This data is also available through the GEE platform and in the Awesome Google Earth Community Catalog

https://mtbs.gov