too. First scrape the bark a tiny bit in a few spots on the branches with your thumbnail to see if there is green under it. If there is, the tree is alive. It doesn't look dead to me.
Then, yes you should begin watering and fertilize it. But before you do that, you really should weed out all that stuff underneath it, in a circle at least a couple of feet wide around the trunk. All those weeds and grass are competing with the little tree for water and nutrients.
After you weed and fertilize, lay down some organic wood chip mulch. It will keep the root zone cooler and more moist and help the tree a lot both through the coming heat of summer but also VERY much help it through winters to come. Just don't pile it up against the trunk, keep it an inch or two away. The mulch layer should be maintained at 3 inches thick or so for good insulation and weed suppression. Add more in fall if you have it, or just pile your dead leaves around the tree, too.
