A Study On The Community Structure,Biomass And Species Diversity Of Platycladus Orientalis Plantation In Songshan Mountain

The community structure, blomass, productivity and species diversity of different age plantations in Songshan Mountain were studied in the paper. By investigated 12 arbors plots, 60 shrubs and 60 herbaceous patches the results showed as following:1. The community structures of the different age plantations were simple. All the other communities were all single layer stand except that Arbor layer showed the double layers based on Quercus variable only in 65- year old plantation. Under canopy evolved into complex of sun plants and shades plants from natural pure sun plants.2. In the Platycladus orientals plantation of different ages, the biomass of per tree's organs in distribution showed such a regularity as stems > branches > leaves; the ratios of there organs in different ages stand were: 52:26:22; 54:27:19; 55:27:18; 55:29:16; 58:28:14 and 59:28:16 respectively.3. The biomass of stand community in different ages of Platycladus oriental is such as 10,17,21,31,44 and 65 ages were 25.208 t· ha-1, 35.778 t·ha-1, 39.21 t·ha-1, 38.786 t·ha-1, 62.9 t·ha-1 and 70.37 t ·ha-1 respectively. The biomasses of arbor layer account for 95.6%, 97.35%, 97.62%, 96.53%, 98.28% and 98.78% of their total community biomass. These results showedan increasing trend of biomass according to different stand ages.4. The rise of net stand primary productivity of different plantation ages in Songshan Mountain Platycladus oriental's communities indicated property of stages. .The net annual primary productivity of 2-10 year-old plantation was 2.689 t·ha-1·'-1, the first growth peak; 1.29 t ·ha-1·a-1 of 10-20 year-old plantation; the net annual primary productivity of 21-31 year-old plantation showed a little reduction. 1.88 t·ha-1 · a-1 of 31-41 year-old plantation, the second growth peak; and the net annual primary productivity of 44-65 year-old plantation reduced rapidly to only 0.367 t·ha-1·a-15. The species richness indices of Placladus oriental's plantation community indicated a gradually increase according to the extension of recovery time. The species of shrubs layer changed to 16 in 65 year-old stand from 8 in 10 year-old stand and from 19 to 24 of herbaceous layer. The changes of the Dmar index of shrubs end herbaceous layer were 1.52-3.257 and 3.91-4.995 respectively.6. The investigated results of different species diversity indices revealed that the species diversity indices of shrubs and herbaceous layer, which belonged to the different ages plantation community in Songshan Mountain Placladus orientalis communities had a little difference, and no clear changing regularity. The diversity indexes showed no clear relations with the biomass of their community.