Changes in the chemical compositions of leaf litter in the canopy of a Japanese cedar plantation
Canopy leaf litter is typically unevenly distributed due to interception by branches and epiphytes and/or due to attachment to branches and tree trunks. Japanese cedar (Cryptomeria japonica) trees hold a large amount of canopy litter that stays attached to foliage and branches for several years before litterfall. Litter retention in the canopy is predicted to affect the chemical composition of litterfall and throughfall. We analyzed the chemical compositions of water-soluble materials washed from the leaves and those of the leaf residues with different leaf litter ages to clarify the effect of leaf-litter retention in the canopy of Japanese cedar trees. Chemical components of the leaf litter after the washing procedure show temporal changes in total carbon, total nitrogen, and carbon/nitrogen ratio just after senescence and prior to litterfall. Higher inorganic ion concentrations in soluble materials from old dead leaves (ODL) dead for more than 2 years suggest the importance of ODL in leaching and catching chemical components in the canopy. Our results show that Japanese cedar canopies retain the various qualities of leaf litter, which are produced by senescence, leaching, and catching dry deposition, and that a large amount of dissolved components leach from dead leaves that are still attached to the canopy.