Structure of Biomass and Productivity in the Mixed Stands of Masson's Pine and Cyclobalanopsis myrsinaefolia

One-year-old seedlings of Cyclobalanopsis myrsinaefolia was planted under the 25-year-old Masson's pine plantation,and developed into closed mixed stand after 16 years of management.By harvesting and measuring the average sample trees collected from the plots,the allocation patterns of biomass and net primary productivity in the mixture and also the pure Masson's pine plantation were estimated and analyzed.The tree biomass was 204.37 t·hm~(-2) in the pure stand,and 245.94 t·hm~(-2) in the mixture.In the mixture,the pine trees in the upper canopy accounted for 81.80% of the total biomass.Allocation to stems was the greatest,making up 64.77% of the sum in pine stand,and 60.17% in the mixture,followed by roots(18.62% and 16.95%),branches (8.99% and 13.46%),barks(6.55% and 6.37%),with foliage the least(1.07% and 3.05%).The spatial pattern of the tree biomass varied greatly between pure and mixed stands,with 67.3% of the total biomass being distributed at the height of 0～10 meters for the mixture,and 53.7% for the pure.In addition,foliage was mainly distributed at the heights of 2～11 m and 17～22 m above the ground in the mixture,but concentrated at 15～23 m height in the pure stand.In the mixture, roots were mostly distributed at the soil depth of 0～20 cm and below 60 cm,occupying 43.3% and 28.2% of the total below-ground biomass,respectively,just like a dumbbell;in the pine stand,the roots increased with the soil depth,forming a pyramid distribution pattern.The net primary productivity(NPP) was estimated to be 13.24 t·hm~(-2)a~(-1) for the mixture,which increased by 80.38% than the pine stand.The NPP allocation to various components of the trees decreased in the order: stemfoliagebranchrootbark in the mixture,but stemrootfoliagebranchbark for the pure.