Litterfall of a subtropical evergreen broad-leaved forest in Okinawa island, Japan

Abstract

The seasonal patterns of litterfalls, such as leaves, woody organs, reproductive parts, insect bodies, and feces, were investigated monthly for three years from January 1999 to December 2001 in a subtropical evergreen broad-leaved forest in the northern part of Okinawa Island, Japan. The total annual litterfall was estimated at 6.66-8.28 Mg ha-1 yr-1. The litterfall was mainly composed of leaves (52.4- 54.8% of the total litterfall), about half of which were from Castanopsis Sieboldii. The species composition of leaf litter was almost consistently the same every month for a year. The leaf litter was separated into two groups: one group, which had a high proportion of the total leaf litter, included C. Sieboldii, Schima Wallichii, Elaeocarpus japonicus, and Cinnamomum Doederleinii; the other group included the other 44 species. The species diversity indexes of leaf litter H’ and J’ showed their minimum values in March, when the leaf litter reached its maximum. There was no significant difference in species rank among years in terms of the annual amount of leaf litter. The mean leaf litter per tree of a given species was significantly proportional to its corresponding basal area, regardless of species and year. The degree of overlap in the seasonal patterns of litterfall components showed that leaves, insect bodies, and reproductive parts are nearly overlapped, but woody organs and feces are more or less exclusive to the other three components. Although the seasonal patterns in leaf litter of C. Sieboldii, S. Wallichii, and E. japonicus were nearly overlapped, the seasonal pattern in leaf litter of C. Doederleinii was almost independent of those of the other three species.