Leaf-litter nitrogen concentration in hinoki cypress forests in relation to the time of leaf fall under different climatic conditions in Japan

Leaf-litter nitrogen concentration was investigated for 17 hinoki cypress (Chamaecyparis obtusa Endlicher) forests in the Kochi region on the Pacific Ocean side and the Kyoto region on the Sea of Japan side in Japan where both the amount of precipitation and frequency of typhoon attacks differ between regions. Leaf properties were predicted from climatic, stand, and soil properties by multiple regression analysis. Fresh-leaf nitrogen was higher in the Kyoto than Kochi regions and was higher where soil C/N ratio is lower. The time of leaf-fall, i.e., 50% of the annual leaf fall, showed a difference of 86 days among the forests and occurred earlier in forests at higher altitudes. The time of leaf-fall at higher altitudes was earlier due to the higher susceptibility to strong winds from typhoons. Leaf-litter nitrogen concentration of annual leaf-fall or winter leaf-fall was lower when the time of leaf-fall occurred later. The results indicate that nitrogen resorption is proficient when leaf-fall occurs later, leading to lower leaf-litter nitrogen concentration.