welcome to TPF!!!
my comments:
#1 - there's nothing in the photo to draw my focus, no subject. there also seems to be a white halo around the leaves, i'm not sure what is causing that.
#2 - i like the idea with the layers, but the tree on the right is not in focus and underexposed.
#3 - reminds me of a tree next to my house, it's exactly like that, dying but gorgeous with the different colours. this one is nice, but the harsh sky on the left is distracting and the trunk, IMO, would be better off to the left (rule of thirds)
#4 - this one is my favourite, brilliant colours. try post processing to blur the background, and maybe next time, don't place the leaf in the middle of the picture, or do it without the stem in the bottom, too much dead space around it.
overall, you're off to a good start =)