Annual and seasonal changes in litterfall of an evergreen broad-leaved environmental protection forest created on reclaimed land

Abstract

The litterfall was periodically measured for seven years in an approximately 6 ha environmental protection forest at reclaimed land in Kawasaki City. Two study plots (10m×10m in each)(plot A : unthinned, plot B : thinned) were designated with 40% thinning in plot B. The annual total litterfall at plots A and B averaged at 7.64ton・ha^<-1>(5.73-8.51ton・ha^<-1>) and 6.68ton・ha^<-1>(4.81-8.49ton・ha^<-1>) respectively. Fallen Leaves formed the greatest portion of the litterfall ; 63.0-85.8% at plot A, and 73.4-85.6% at plot B. At plot A, Persea thunbergii leaves amounted to 34.2-59.8% of the fallen leaves, followed in order by Castanopsis cuspidate var. sieboldii and Elaeocarpus sylvestris var. ellipticus. At plot B, Persea thunbergii formed 48.5-73.0%, followed in order by Elaeocarpus sylvestris var. ellipticus and Castanopsis cuspidata var. sieboldii. The amount of fallen leaves at the 40% thinned plot returned to match the unthinned one in three years. The amount of fallen branches was greater at plot A than B, and plot B showed greater variation from year to year. Reproductive organs consisted primarily of flowers of Castanopsis cuspidata var. sieboldii and nuts of Quercus glauca. Seasonal changes in litterfall displayed the same characteristics as a natural evergreen broad-leaved forest ; showing a drastic increase in May, with high litterfall continuing through late summer until September. It became clear that thinning does not affect the seasonal litterfall pattern. Contrary to the clear seasonal pattern of leaves, the amount of fallen branches did not show any distinctive seasonal fluctuations, but increased as a result of typhoons and strong winds.