DISTRIBUTION,DECOMPOSITION AND NUTRIENT RETURN OF THE FINE ROOT IN PURE Cunninghamia lanceolata, Michelia macclurei AND THE MIXED PLANTATIONS

Soil corer was used to investigate the distribution of fine root and a traditional method of nylon litter bag to measure the decomposition in pure Cunninghamia lanceolata and Michelia macclurei var Sublanea ,and the mixed plantations.Nutrient returns of N,P,K,Ca and Mg in the above three plantations were estimated based on the decomposition experiment.The vertical distribution of live fine root for pure M.macclurei stand was the most superficial,the mixed stand was intermediate,pure C.lanceolata was the least.The fine root of M.macclurei decomposed more quickly than that of C.lanceolata because of its higher original nutrient content and lower C:N ratio.Nutrient return from fine root was largest in pure M.macclurei ,the mixed stand intermediate,and pure C.lanceolata the least.In the mixed stand,returns of N,P,K,Ca and Mg from fine root decomposition were 33 38%,5 82%,269 33%,34 12% and 376 08% of that from decomposition of leaf and twig litter respectively.It is suggested that fine root plays an important role in nutrient cycling of the stands.