| However, this is not the only factor and just as fruit trees have a main season crop and an off-season crop, patterns have also been observed in which airborne pollen levels fluctuate every other year or on a 2-3 year basis. |
しかし、必ずしもそればかりの影響のみにては決まらず、果樹などにおいて表作・裏作があるのと同様に、飛散量は1年おきに増減を繰り返すか、2～3年で増減を繰り返すパターンがよくみられる。 |