scrubland vs underbrush

scrubland

noun
  • A plant community characterized by scrub vegetation, consisting of low shrubs, mixed with grasses, herbs, and geophytes. 

underbrush

noun
  • The small trees and other plants that clutter the floor of a forest. 

verb
  • To clear (an area) of underbrush. 

  • To work among the underbrush. 

How often have the words scrubland and underbrush occurred in a corpus of books? (source: Google Ngram Viewer )