heathland vs scrubland

heathland

noun
  • A tract of scrubland habitats characterised by open, low growing woody vegetation, found on mainly infertile acidic soils. Similar to moorland but with warmer and drier climate. 

scrubland

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

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