Trees are definitely alive. I mean, not just alive, but aware, conscious. John F. Carlson in his 'Landscape Painting' classic also implies that trees have a higher state of being than your average lumberjack would acknowledge, so that's good enough for me.
Tolkien seems to have been preoccupied with trees. Although dare I say it in this Lord of the Rings besotted generation, Tom Bombadil and the Ents were his least gripping moments in what I would say was a great read (notice Tom Bombadil isn't in the film).
The above trees were 'meditating' near me for a few days some years ago in Izmir Turkey and I was charmed by them.