The litter fall and its nutrient contents of an old beech stand in Northern Honshu, Japan were measured during the mast and lean years. The weights of litter fall and nutrients, especially N, P and K, returned to the soil by litter, were markedly higher in the mast year than in the lean years : the weights of litter fall and N, P and K returned in the mast year were as much as 1.5,2.1,3.3 and 2.7 times that in the lean year, respectively. This was due to the vast amount of fallen reproductive parts (male flowers, seeds and cupules) and the much higher N, P and K contents of seeds, and the higher N and P contents of male flowers than those of other parts. During the mast year, the weight of fallen reproductive parts was 0.7-0.8 times the total litter fall during the lean years, while N, P and K weights of fallen reproductive parts also exceeded those returned by a total lean year litter fall. These facts suggest a unique physiologically-mediated nutrient production response of beech in the mast year, but the mechanism has not yet been elucidated.
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