Both photos were immediately interesting to me, so kudos for that. The tree kind of looks like an alien creature with its arms extended out above its head--good catch on that.
As a matter of personal taste here is what I would have done differently:
- straight horizons, as already mentioned
- a less tight crop on the tree
- broader DoF on the twig to get the whole thing looking sharp
The "single tree" is a photographic cliche, however, I think you pull it off here because this particular tree is so unusual with its high, barren branches and filled out lower ones. Also, the misty and empty background helps tremendously. I also really like how you processed it. It has a haunted quality, like a collodion wet plate process. Agree with the others that you could straighten the horizon.
As jenko said, kinda cliche... for both of them, really. Still, some interesting elements, but not enough to really stand out. These shots suffer from the usual "8,000,000 people have taken shots like this" problem. This includes waves crashing into rocks, sunsets, etc. There's just no way you're going to come up with something that's really jaw-dropping because it's been done to death.