In this part the following words have the meanings indicated. “Licensed tree expert” means a person who has received from the Department a license displaying the person’s qualifications to practice as a tree expert. “Tree expert” means a person who represents to the public that the person is skilled in the science of tree care or removal and who, whether in the business of the person or as the employee of another person and whether under the title of arborist, tree specialist, tree surgeon, tree expert, or otherwise, engages in the business or work of the treatment, care, or removal of trees for compensation by: Making diagnoses, prescribing, and supervising the treatment for trees; or Trimming, pruning, thinning, cabling, shaping, removing, or reducing the crown of trees. “Tree expert” does not include: A person engaged in commercial logging or timber harvesting operations as defined in § 5-1601 of this title; A person engaged in the installation of underground facilities or any associated site construction; or A person who treats, cares for, or removes a tree, as described in paragraph (1) of this subsection, that is 20 feet tall or less.