Seasonal dynamics of litter accumulation in major forest communities on the northern slope of Changbai Mountain,Northeast China

Litter is an important component of the nutrient cycle in forest ecosystems and a key link of substance and energy flows.The changes of nutrient and energy in different forest communities can be detected by examining the dynamics of litter accumulation.To study litter accumulation and its seasonal dynamics in four major forest communities on the northern slope of Changbai Mountain(Broad-leaved Korean Pine forest(BlKP),Asian white birch forest(AwB),David poplar forest(DP),and Spruce-fir forest(Sf)),we harvested litter accumulated on forest floor at the beginning of each month from May to October in the growing season of 2006.The results showed the total litter accumulated in the four communities was significantly different(P0.05) and the ranking from high to low was BlKP(6.43t/hm2),AwB(6.02t/hm2),Sf(5.51t/hm2),and DP(5.50t/hm2).Among the four communities,undecomposed leaves and twigs accounted for more than 50% of the total litter,partially-decomposed litter for more than 35%,and flowers,fruits and barks for less than 10% and 5%,respectively.The seasonal dynamics of litter accumulation showed two peaks in BlKP,AwB and DP in May and July,and one in Sf in July.The seasonal dynamics of litter components in BlKP,AwB and DP at similar altitudes were comparable In particular,the seasonal trends of the litter components in AwB and DP were identical,high twig,bark and partially-decomposed litter in May and July,but a steady decline of leaf litter during growing season.In the BlKP,however,leaf and twig litters were high in May and July.The Sf at high altitudes had different litter dynamics from other three forest communities,starting to increase in May,reaching the peak in July,and showing a gradual decrease after August.The comparison of monthly leaf litter accumulation between BlKP and Sf suggested that the peak leaf litter of BlKP in July was largely determined by broad-leaved species including Acer mono Maxim,Tilia amurensis Rupr,and Fraxinus mandshurica,instead of Pinus koraiensis,whereas the peak value of Sf depended on conifer species such as Pinus koraiensis,Abies,Picea and Larix.