十万个为什么·科学阅读30篇（5）
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Why Do Some Trees Lose Leaves in Winter?
为什么有些树在冬天落叶？
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Trees drop leaves to save water when it's cold.天气寒冷时，树木落叶以节约水分。
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Winter soil is frozen, so roots can't drink well.冬季土壤冻结，树根难以吸水。
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Leaves lose too much water through tiny holes.叶片通过微小气孔散失过多水分。
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Trees seal off leaf stems before letting them fall.树木在落叶前会封闭叶柄。
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New leaves grow again when warm weather returns.天气转暖后，新叶重新长出。
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This helps trees survive dry, chilly months safely.这有助于树木安全度过干燥寒冷的月份。
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Not all trees do this—evergreens keep leaves year-round.并非所有树木都如此——常绿树全年保持叶片。
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Deciduous trees use this smart water-saving trick.落叶树采用这种聪明的节水策略。