California Code, Public Resources Code - PRC § 752

(a) “Professional forester,” as used in this article, means a person who, by reason of their knowledge of the natural sciences, mathematics, and the principles of forestry, acquired by forestry education and experience, performs services, including, but not limited to, consultation, investigation, evaluation, planning, or responsible supervision of forestry activities when those professional services require the application of forestry principles and techniques.

(b) A professional forester is licensed to perform forestry services only in those areas of expertise in which the person is fully competent as a result of training or experience.  In order for a professional forester to fulfill all of their responsibilities with regard to a particular activity on a site, if the expertise that is prudently required exceeds the expertise possessed by the professional forester in that regard, the professional forester may need to utilize the services of other qualified experts, including, but not limited to, archaeologists, botanists, civil engineers, ecologists, fisheries biologists, geologists, hydrologists, land surveyors, landscape architects, range scientists, soil scientists, or wildlife biologists.  This article shall not preclude those other environmental professionals from the application of their knowledge in their field of expertise outside the practice of forestry, as defined in Section 753.