Abstract:

Dynamics of litter production, nutrient return and decomposition of four Eucalyptus grandis plantations investigated in Hongya County, Sichuan Province. The results indicated:1)The litter production of the E. grandis plantations increased with the increase of the standing density. The monthly variations of litter production were similar in four Eucalyptus grandis plantations, and peak occurred in May and the lowest values occurred in January;2) The ranked order of the nutrient returns was N > K > Ca > Mg > P, The annual macro_element returns of the four eucalyptus forests were 95.32, 86.90, 67.72 and 66.37 kg·hm^-2, respectively;3) The leaf was the main components of the nutrient return, larger nutrient returns occurred in spring and summer;4)The average loss rate of branch and leaf were 18.2% and 36.1% respectively;5)The annual decomposition rate estimated by the exponential decay model were 0.176～0.214 and 0.383～0.445,the half declining were 3～4 years and 1～2 years respectively,95% declining were 14～17 years and 6～8 years respectively. The order of releasing speeds of litter was Mg>Ca>K>N>P,P immobilization was observed, N showed increased in 182 d and thereafter decreased over rest of the trial, K、Ca and Mg loss most in quantity.

Key words: Eucalyptus grandis plantation, litter production, nutrient return, decomposition rate