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1·Based on warming experiments using greenhouses, biologists have known for some time that shrubs will grow at the expense of the other tundra plants when the climate warms.

透过在温室进行的暖化实验，生物学家已经知道：当气候温暖，灌木会在苔原植物受损时取而代之。

2·The climate gradually takes changes from subtropics, temperate zone, cool temperature zone and arctic tundra.

气侯从亚热带、温带、寒温带到亚苔原带逐渐变化。