First off, welcome to the board, and while I'm not great with this kind of photography there are plenty of people here who would be glad to help. And in order to help us do that, when you do post photos please number each photo so that we have an easier time responding.
alright, well, I'm not a huge landscape/nature guy, but I'll give you what I see real quick.
1, probably needs the most work. The problem is the subject, I'm sure it was probably the fence, but much of the fence is out of focus, and in both corners where it makes the entrance and exit it is still going (we never see a starting or ending point. Also, the tree is chopped off and you also chopped off half of the bushes. Finally, the colors look a little off to me (unlike the rest of the photos this one looks more hazy).
2.) Nice sharp photo, I like the colors quite a bit, though it may be a bit dark. If I were to try to improve it I might crop off that green leaf or whatever on the right side of the photo. It's a bit distracting... This was my favorite of the set.
3.) Pretty nice photo, my nits on this photo are that there are details on the flower that have been blown out, and the left side feels rather busy with out of focus items.
4.)Probably my second choice for the best photo. I like all the lines made by the tree trunks. The sky is rather bland, but you did a good job keeping it to a minimum. Only question here is the very odd crop, what was it for?