抄録
Nutrient inputs via litterfall and associated nutrient accumulations and releases in the litter layer were investigated in 7-year-old Acacia mangium Willd. plantation stands in Indonesia. Annual N, Mg, Ca and K inputs via litterfall were 230-235, 21-26, 157-179 and 131-157kg ha-1 yr-1, respectively and the contributions of phyllode litterfall to these nutrient inputs were over 60%. Nutrient inputs via litterfall increased from dry to wet seasons being strongly associated with reproductive litterfall inputs as well as phyllode litterfall inputs. Annual mean N, Mg, Ca and K accumulations on the forest floor were 172-235, 12-14, 52-88 and 42-47kg ha-1, respectively. There were no clear seasonal variations in nutrient amounts on the forest floor. The peak of mass loss of phyllode litter was observed in the late wet seasons, and its seasonal change was coincided with the rainfall seasonality. Reflecting mass losses of reproductive and twig litters, however, seasonal variability in mass loss of whole litter became more complex. Nitrogen and Mg releases from litter layer tended to increase in the late wet seasons being affected by the retarded releases of these nutrients from fleshly fallen litters in addition to the increased mass loss of phyllode litter in the periods. Calcium releases from litter layer showed no significant seasonal variations reflecting the irregular seasonal changes in Ca release from twig litter rich in Ca. Meanwhile, the seasonal variation in K release from litter layer coincided with the seasonal changes in K inputs via litterfall.
