Litterfall, decomposition and nutrient release of Shorea robusta and Tectona grandis in a sub-tropical forest of West Bengal, Eastern India

We studied leaf litter fall,decomposition and nutrient release patterns of Shorea robusta and Tectona grandis by using a litter bag technique to better understand the release pattern of nutrients to soil from leaf litter.Annual litterfall varied from 13.40 ± 2.56 t ha-1a-1 for S.robusta to 11.03 ± 3.72 t ha-1a-1 for T.grandis and the decay constant（k） of decomposed leaf litter was distinctly higher for T.grandis(2.70 ± 0.50 a-1) compared to S.robusta(2.41 ± 0.30 a-1).Biomass loss was positively correlated with the initial litter C,WSC,C/N and ash content in S.robusta and N,P and K concentration for T.grandis.Biomass was negatively correlated with lignin and L/N ratio for S.robusta and L,WSC,L/N and C/N ratio for T.grandis（P\0.01）.Nutrient use efficiency（NUE） and nutrient accumulation index（NAI） of S.robusta was higher than for T.grandis.The retranslocation of bioelements from senescent leaves ranked as P [ N [ K.Annual N,P and K input to soil through litterfall differed significantly between the two species in the following order:N[K[P.S.robusta was superior in terms of K and P return and T.grandis was superior in terms of N return.The two tree species showed a similar patterns of nutrient release（K [ P [ N） during decomposition of their leaf litter.Nutrients of N,K and P were the primary limiting nutrients returned to soil through litterfall with important roles in soil fertility and forest productivity.