Litter decomposition plays an important role in the energy flux and nutrient cycling in forest ecosystems. The forest dominated by Cyclobalanopsis glauca is a typical subtropical evergreen broad-leaved forest in East China. This work was carried out in such a forest in Jiande, Zhejiang Province, East China, to study the nutrient dynamics in litter decomposition with the litterbag method. The litters used in this work included leaves and branches of C. glauca, Quercus serrata var. glandulifera, Woodwardia japonica and Dryopteris chanmpionii. The concentrations and mass remaining of C, N, P, K, Ca, Mg, Mn, Cu and Zn were monitored over a 24-month period consecutively.The results show that: After two years, the annual average release rates of elements, C, N, P, K, Ca, Mg, Mn, Cu and Zn, were 41.31%, 38.48%, 42.86%, 47.14%, 21.13%, 44.48%, 32.98%, 10.68%, 11.50% in leaf litter of C. glauca; 44.06%, 38.56%, 39.71%, 47.22%, 36.22%, 40.91%, 37.50%, 3.80%, 6.10% in leaf litter of Q. serrata var. glandulifera; 40.13%, 39.58%, 33.33%, 48.19%, 21.11%, 47.22%, 25.00%, 5.00%, 18.65% in leaf litter of ferns; 29.69%, 30.77%, 33.33%, 43.19%, 18.67%, 35.71%, 33.33%, 7.78%, 26.60% in litter of thin branch; 27.91%, 34.78%, 33.33%, 42.31%, 19.85%, 40.00%, 30.00%, 16.21%, 17.52% in litter of thick branch, respectively. K and Mg had the higher release rate, while Zn, Cu and Ca had the relevant lower rate. P, Zn, Cu, Ca, N and Mg all accumulated in a certain degree in the decomposition process. The mass remaining of leaf litter had a negative correlation with the mass remaining of N, Ca, Mn, Cu and Zn, while it positively correlated with that of C, P, K and Mg. Release mode of the dry matter was closely correlated with each kind of nutrients. Release mode of C, N was linearity function, that of P and Mg was function of function, and that of K was logarithm function, the remainder rate of Ca, Mg, Cu and Zn had more than three best models. Cu, Zn, Ca and Mg could accelerate the decomposition of dry matter. Initial N content and C∶N ratio were litter chemistry parameters used to predict the rate of decomposition.
The C∶N ratio is a valuable index which can indicate the speed of decomposition. It was considered that during decomposition N would be immobilized in the microbial biomass. There had the same relation between C∶P ratio and P. In our work, net immobilization of N occured when critical C∶N ratios was about 20 in litter. While, critical C∶P ratios was about 600 in litter, the net immobilization of P occurred. Decomposition of leaf litter was influenced by both N and P in the first year, while N became the key factor in the second year. The decomposition process in the two years was more closely correlated with C∶N ratio.