Hi Jessica,
Thanks for submitting this image. I have to confess to not having that much experience with star trails, at least in the digital era. Twenty years ago it was easy to put a mechanical camera onto a tripod and leave the shutter open for an few hours without having to worry about batteries and multiple exposures. Today it's near impossible to find a camera with a shutter that will stay open all night!
As you mentioned, this photo is made up of about 220 one-minute exposures that have been layered together in Photoshop and joined using the Lighten layer option. Overall the technique has been successful.
If I was to change one thing, though, it would be the base exposure for this image. I feel the stars are just a bit on the bright side, to the point that it's a little too bright. If anything, I would perhaps keep the shutter speed the same, but maybe close down the aperture one stop (from f/3.5 to f/4.5 or f/5.6).
Now, in as much as I think star trails can be beautiful, I think they can also be like clouds; nice to have in a picture, but what about the foreground?
For this simple reason I think I would have like to have seen more of the landscape, just for the sake of creating a sense of place. Of course another option for you might be to place a mirror across the foreground to experiment with the reflections. All food for thought!
Good luck with your next shoot… cheers, Anthony