Litter production and nutrient return in two natural forests and a Cunninghamia lanceolata plantation in Wanmulin Nature Reserve

Litterfall represents a major biological pathway for element transfer from vegetation to soils.Seasonal variations in litter production and litter nutrient return affect stand nutrient cycling.Although considerable data exist for litter production and nutrient cycling in different forest ecosystems of the world,relatively few studies were carried out in forests of southern China.The primary purpose of this study was to determine litter production,seasonal dynamics and nutrient return in two natural forests of Tsoongiodendron odorum(TSO) and Altingia gracilipes(ALG),and an adjacent 29-year-old plantation of Chinese fir(Cunninghamia lanceolata,CUL) in Wanmulin Nature Reserve in Jianou,Fujian,during a period of 20002002.Mean annual total litterfall over 3 years of observations varied from 4.63 t·hm~(-2) in the CUL to 6.74 t·hm~(-2) in the TSO;of total litterfall,the leaf contribution ranged from 62 % to 69 %. Litterfall in the ALG showed an unimodal distribution pattern with a peak in March or April of each year,while for the TSO,the litterfall peaks occurred in March and June-August.Litterfall in the CUL peaked in March(or April),June-August and November(or December),respectively.The rank order of the three forests,according to Ca and Mg returns from total litterfall,was different from the order when rank was according to total mass of litterfall.The highest annual Ca returns from total litterfall were noticed in the CUL.The amounts of N,P,K and Mg potentially returned to the soil were the highest in the TSO.The leaf fraction provided greater potential returns of N,P,K,Ca,and Mg to the soil than other litter fractions.The results of this study demonstrate that natural forests have a greater capability for maintaining site productivity than the monoculture coniferous plantation due to higher amount of aboveground litter coupled with greater nutrient returns;therefore conservation of natural forests is recommended as a practical measure in forest management to realize sustainable development of forestry in mountainous areas of southern China.