Here are a few resources I recommend as being especially helpful.
Great little guide to the theory, guidelines and how to of forest bathing. If you buy one book, this is it.
“Your Guide to Forest Bathing” by M. Amos Clifford. 2018: Conari Press.
Lots of information about forest bathing including the research, a blog with many different topics, and a schedule of immersive experiences and guide training.
Association for Nature and Forest Therapy Guides. https://www.natureandforesttherapy.org/
A summary of the research on Forest Bathing impact on mental and physical health.
“Shinrin-Yoku (Forest Bathing) and Nature Therapy: A State-of-the-Art Review”. Margaret M. Hansen. Int J Environ Res Public Health. 2017 Aug; 14(8): 851