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Boreal forest soils are acidic and short of nitrogen. Why does that favor conifers over broadleaved trees?
AConifers drop their needles each year
BConifers fix nitrogen in their own roots
CConifers keep their needles for years
DConifers grow only in acid free soils
Answer & Solution
Correct answer: C. Conifers keep their needles for years
1. Leaves are rich in nitrogen, so building them costs a tree nitrogen.
2. A deciduous tree drops its leaves each autumn and must build a whole new set each spring.
3. That annual rebuild is expensive where soil nitrogen is scarce.
4. Conifers keep their needle shaped leaves year round instead.
5. Holding onto nitrogen rich needles spreads that cost over many years.
6. Evergreen needles also let a conifer start photosynthesizing earlier in spring.
7. Saying conifers drop needles annually removes the very advantage being described.
8. Nitrogen fixation in boreal conifer roots is not what makes the difference here.
_Source: OpenStax Biology 1e (CC BY 4.0), Chs 44 and 46, section 44.3 Terrestrial Biomes_
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