Composition of Dispersed Seeds and its Effects on the Understory Vegetation of the Fragmented Secondary Forests

Abstract

Species composition of understory vegetation and seed dispersal were surveyed at a fragmented secondary forest in the campus of The Nat. Inst. of Agro-Environ. Sci., in Tsukuba. Almost all the tree species were bird-dispersed plants, and 40 percent of them were dispersed from the surrounding landscape to the forest. The species composition of fragmented secondary forest was related to the composition of seeds dispersed from the surrounding landscape. The street tree population (Sophora japonica) planted near the fragmented forest collected 49 percent of the amount of seeds dispersed from the surrounding landscape and supplied the seeds of Soph ora japonica to the forest 4.3 times as many as the amount of seeds dispersed from the surrounding landscape. These suggest that street tree population of native species located in the vicinity of fragmented forest may be useful in maintaining desirable composition of seed inputs.