一．阅读理解
A
Even if trees cannot walk, they are still on the move.
In parts of the Arctic, entire forests are moving northward. Across the Arctic, temperatures are rising faster than anywhere else in the world. As that happens, the tree line that marks where forests stop and the treeless tundra(冻原) starts has been shifting northward. Trees growing along the tree line must protect themselves from the cold wind. To do this , plants tend to grow horizontal (水平的) branches low to the ground. The energy it takes for trees to grow this way means they don't have enough energy to make seeds.
