Question

In ecology, PPDF stands for

Answer 1

In ecology, PPDF stands for Ponderosa pine–Douglas-fir, It is given the name of pine, but corresponds to the genus Pseudotsuga, and is marketed under different names, such as Oregon pine, Oregon, Douglas-fir and Douglas fir.

Answer 2

In ecology, PPDF stands for Ponderosa Pine Douglas Fir.

In general, PPDF is used as a security of a document which exceeds what someone can do within the PDF software were itself. In ecology its PPDF genus is Pseudotsuga.
Other names which are marketed include
Douglas fir, Oregon, and Oregon pine.