Abstract
The dispersal mechanism of Japanese yew (Taxus cuspidata S. and Z.) seeds by animals, especially birds, was studied in the Tomakomai Experimental Forest of Hokkaido University in southern Hokkaido. Two sample trees ( I and II) were investigated for seed production and their consumption by animals. Trees I and II produced 36, 628 and 2, 785 seeds, respectively. The greater part of these seeds were consumed by birds (I: 73%, II: 46%) and rodents (I: 14%, II: 34%). About 5% of all the seeds, however, were scatter-hoarded by the varied tit (Parus varius T. and S.) which stored 37% of them in bark fissures and among the needles of coniferous trees and 63% of them on the ground. The seeds on the ground were put on particular sites such as around the roots of trees and on steep and bare slopes. These caches were related to the distribution of yew seedlings. Moreover, the frequency of dispersed seeds plotted against distance was related closely with the density of the seedlings. From these results, the scatter-hoarding of seeds by the varied tit was suggested to be important in the dispersion of yew. The relationship between yew and the dispersal agents, including not only the varied tit but other animals, also is discussed.
