Inter-annual variations of leaf-fall phenology and leaf-litter nitrogen concentration in a hinoki cypress (Chamaecyparis obtusa Endlicher) stand

Inter-annual variations in leaf-fall phenology and leaf-litter nitrogen concentration were investigated for 13 years in a coniferous plantation of hinoki cypress trees (Chamaecyparis obtusa Endlicher) in Kochi, southern Japan. Mean annual nitrogen concentration in the leaf litter ranged from 5.97 to 7.12 g kg⁻¹. The removal of 30 percent of the trees’ basal area in the 3rd year had little effect on leaf-litter nitrogen concentration. The nitrogen concentration in the leaf litter was not correlated with the mean temperature from March to October. The leaf-fall duration, i.e., time between 10 and 90% of the annual leaf fall, was shorter and the leaf-litter nitrogen concentration was lower when the solar radiation from March to October was higher. The results suggest that the hinoki trees shed their leaves abruptly and have lower leaf-litter nitrogen concentration when the solar radiation is higher and that effects of temperature on leaf-fall properties may not be strong in warm climate areas.