I would go with number 4 because I'm not much for nature photography (being in nature , sure, but looking at a 4 x 6 of nature, no thanks), and because the only human subjects are decidedly uninterested, and consequently uninteresting. I like the geometry of number 4 and I guess I just like rusty old steel stuck where it doesn't seem to belong.
Kinda feel like number one is showing us the entry point into another world, but it needs to be reframed a bit to show more of the gate. It's my favorite though.
My favorite is the one with the red plant. It grabbed my attention the most because of its color against the monochromatic background.
I liked the framing in the first shot and the perspective of that last photo. Though photos of nature are not that interesting, the perspective is new and a different way of looking at nature so I applaud you.
The last one's my favorite.
I like the splash of red in number 3. :) cool pictures! :)
At first glance, four was my favorite, but going through this essay again, I like number one the best. It maybe could be cropped a little differently, but the depth of field and the path in the background pulls your eye through the photo.
I like the first one because it makes you feel like you're peeking through something