I was on a mountain the other day and had a moment where I just had to stop and take it all in. I felt insignificant (in the best way) and just stopped to admire where I was. The closest words I could find was something along the lines of biophilia, or the German word Waldeinsamkeit.
While not nature specific, awestruck seems to be suitable.
- Entranced: If you are entranced by someone or something that is very interesting or beautiful, you cannot stop watching him, her, or it:
The children sat silent on the carpet, entranced by the puppet show.
[Cambridge Dictionaries Online]
Synonyms: captivated, enraptured, enthralled.