|
训练17 阅读理解＋完形填空＋语法填空＋短文改错 (建议用时45分钟) .阅读理解 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. But as Earth’s climate has been warming，trees no longer have to just grow horizontally.Many can instead grow up toward the sky.This takes less energy.And with all that leftover energy，these trees have started producing more seeds.This happens especially in places where white spruce (白云杉) grows. White spruce，which is a North American tree，is quite able to produce a lot of seeds，which can move long distances in the wind.When windblown seeds end up on the tundra | 
