2. (8 points) A poplar tree, a willow tree, a locust tree, a birch tree, and a sycamore tree are planted in a row, with the distance between adjacent trees being 1 meter. The distance between the poplar tree and the willow tree, and the locust tree is the same, and the distance between the birch tree and the poplar tree, and the locust tree is the same. Therefore, the distance between the sycamore tree and the birch tree is $\qquad$ meters.
【Answer】Solution: The distance between the poplar tree and the willow tree, as well as the locust tree, is equal. Therefore, the possible positions of the three trees could be: Willow $\square$ Poplar
Locust, Willow Poplar Locust $\square \square$, $\square$ Willow Poplar Locust $\square$, $\square \square$ Willow Poplar Locust, where $\square$ indicates an unknown position.
Since the distance between the birch tree and the poplar tree, as well as the locust tree, is also equal, the only possible arrangement is: Willow $\square$ Poplar Birch Locust, with the remaining position being the plane tree.

Therefore, the distance between the plane tree and the birch tree is 2 meters.
The answer is: 2.