ブナ(Fagus crenata)堅果の散布前捕食の影響 : 袋掛け実験による評価

抄録

We conducted an experiment to evaluate the effectiveness of preventing predispersal predation on nut viability in beech (Fagus crenata Blume) by bagging a single canopy tree in an old-growth stand of central Japan over two consecutive years with different nut production. To prevent predation on predispersal nuts, the bagging treatment began in mid June of both years. Seed trap sampling of fallen nuts and direct sampling of cupules were also conducted to monitor seasonal changes. Although viable nuts were less productive in the sample beech than in the surrounding beech stand, the bagging treatment increased the proportion of viable nuts from the sample beech by approximately eight fold in the first year (from 4.9% to 41.3%) and five fold (from 2.4% to 12.5%) in the following year. Thus, at an individual level, predator exclusion by bagging increased the percentage of viable nuts by reducing predispersal predation. The results of this experiment confirm that predispersal insect predation is a major factor controlling the viable nut rate in beech.