Foresters had long assumed that salvage logging benefitted the environment by reducing fire risk and helping conifer seedlings regenerate. In order to determine if this was true, Donato's team treated it as a hypothesis and tested it.
Using the following options to complete the following:

higher, lower, dependant, independent

Hypothesis:
Salvage logging helps conifer seedlings regenerate and reduces fire risk.
Predictions:
If a site is logged after a fire, then conifer regeneration should be at that site than at a site that was not logged.
If a site is logged after a fire, then the density of woody fuels should be at that site than at a site that was not logged.
Test:
Donato and his team studied two types of plots: some that were burned but not logged and some that were burned and logged. Logged vs. not-logged represents the variable in this study. In each plot, Donato's team measured conifer regeneration, a(n) variable, and the density of woody fuels, a(n) variable .