Effect On Chinese Fir Second Rotation Growth Of Different Managements

Chinese fir(Cunninghamia lanceolata) is planted widely in south China because of the high quality timber and the fast-growing character, pure Chinese fir plantation have been replanted on the same site in successive rotations,lead to serious problems of soil fertility degradation which has been an important restricting-factor of forestry development in a certain extent. The soil fertility degradation of Chinese fir forestry has become a ecological problem ,which has been attended by academia .We design the orthogonal experiment L₉(3⁴) and set different normative plot with different ingathering way,different soil-Preparation way and different cut-residue treatment way at the forestry ruin of the first rotation forest to study the growth status ,decomposing dynamic of cutting- residue and soil fertility of the young second-rotation forest . The result shows:1.We find that the decline extent of diameter of brest-height(DBH) is more than the height .The experiment result shows: With the adding of the rotation the growth of height and the DBH represent declining trend . Compared with the first rotation the DBH of Chinese fir reduced by 35.00%⁶0.94% in different normative plots ,and the growth of height reduced by 20.68%⁴2.73%. The optimum factor which influences the growth of DBH and height is the ingathering way .The minimum factor is the treatment way of cut-residue .The best assembled mode is only harvest the trunk of trees, block plough, slashing burning.The optimum factor which influences the biomass of superstratum section, underground section and the total biomass .The minimum factors are in difference they are only harvest the trunk, block plough and bespread the cut-residue uniformly.2. The most important factor which influences the content of nitrogen in leaf ,branch ,and thin root is the ingathering way ,and the minimum factor is treatment way of cut-residue .The content of N in trunk and cortices is been influenced by treatment way of cut-residue ,and the soil-preparation way is the minimum factor .The optimum factor is soil-preparation way which influences the nitrogen content in thick root and the minimum factor is the soil-preparation way .there are different assemble modes to the different organ : Leaf; only harvest the trunk, block plough and cut-residue, grass and shrub stacked on the forestland. Branch, ingathering branches that the diameter is more than 2cm on the forest land including arbor and shrub, ditch plough (plough 1m,withhold 2m) and make the cut-residue , grass and shrub stacked on the forest land .Cortices , ingathering branches that the diameter is more than 2cm on the forest land including arbor and shrub , ditch plough (plough 1m,withhold 2m ) and bespread the cut-residue , grass and shrub on the land .Trunk and thin root ,only harvest trunk ,block plough and slash burning .Thick root , only...