Is it true that Cedar trees are 1/3 deciduous ? if so, when do they lose their needles and when grow back again?

do they lose like the bottom 1/3 of their needles? when and why? or how depends?
Update: are they often at the BOTTOM 1/3? someone told me that the Deodor Cedar is 1/3 deciduous? when do they lost their needles the most and where? and why?
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