Leaf traits, litter decomposability and forest floor dynamics in an evergreen- and a deciduous-broadleaved forest in warm temperate Japan

Abstract

Thereisaconsistentrelationshipbetweenthelitterquality,litterdecayratesinlitterbagsandforestfloordynamics ofconiferousforestsanddeciduousbroadleavedforests(DBFs)inboreal-to-cooltemperateregions.Weexamined whether there was a similar relationship between an evergreen broadleaved forest (EBF) and a DBF in warm temperateJapan.Theleaftoughnessandleafmassperleafareawassignificantlyhigher,andinitialdecomposability, intermsofmasslossrateandCO2emissionrate,ofthelitterinlitterbagswassignificantlylowerforQuercusacuta, anevergreenoakthatisdominantinEBFthanforCarpinuslaxiflora,PrunusyamasakuraandQuercusserrata,three deciduous species that are co-dominant in DBF, respectively. Nevertheless, the CO2 emission rate of the A0-layer tended to be higher in EBF than in DBF, and litter turnover rate did not differ between them. The discrepancy between the initial litter decomposability and the forest floor dynamics across the two functional types was ascribed to activities of microorganisms and surface-living earthworms that were affected by the water content of the A0-layer. We concluded that due to the crucial effect of moisture on decomposition, the powerof substrate quality for predicting forest floor dynamics in EBFand DBFwas smaller than that in coniferous forests and DBFs in boreal-to-cool temperate regions where temperature is a major factor controlling decomposition.