| The structure characteristics of biomass and spatial distribution rule of root system of Pinus massoniana are systemic investigated in acid rain area of Chongqing, and the potential impact of acid deposition on them was discussed as well. The results would provide basic data for the more research in the fields of energy flow, matter circulation and health value of forest ecosystem.The study on the structure, distribution character of biomass and productivity of natural secondary forest of Pinus massoniana in Tieshanping of Chongqing shows that the primary productivity is 8.34t hm~-2 a~-1 and the biomass is 146.08t hm~-2, of which the distributing sequence of the biomass is: tree stratum (87.43%) >humus layer (5.65%) >undergrowth( 5.46% )>herb( 1.46% ). The total biomass of the tree layer is 127.72 thm~-2 of which distributing sequence of different organs is that trunk (93.01 thm~-2 ) >branch (14.29thm~-2) >root (11.84t-hm~-2) >bark (5.66thm~-2) >needle (2.92thm~-2) . Regarding the vertical structure of biomass of each type of organ, the biomass of trunks under the height of 10m accounts to 81.13% of its total, and its branches accounts to 82.25% between 12m and 16m as well as one -year-old needles is the proportion of 93.25% between 12m and 18m. For the root in its about 76.45% is concentrating the lay of 0~ 40cm.Through the trunk analysis of different dominance grades' Pinus massoniana, the percentage of biomass aboveground and root is more 90% and less 10% respectively, and the order of distribution proportion of biomass in different organs is: trunk (73.5%) >branch (10.6%) >root (8.0%) >bark (5.3%) >needle (2.7%) .The order of biomass proportion in different root classes is: stump (>70mm , 55.0%) >large-sized root (10-70mm, 37.7%) >middle-sized root (5~10mm, 3.3% ) >small-sized root (2~5mm, 2.9 % )>fine root(<2mm, 1.1%), the proportion of stump and large-sized root in total biomass is more than 90%, and the other part is less than 10%. There is a best positive correlation between the root system biomass and growth status of individual tree, which includes height, diameter at breast height, needle biomass and aboveground biomass of individualtree;There is also a notable negative correlation between defoliation rate and four indices, including the ratio of root system biomass to area of DBH, density of fine root, biomass of one-year-old needle and one-year-old twigs biomass.The field research methods of soil coring and digging are used, to measure the distribution of roots and to collect root samples. In the laboratory, the sampled cores and roots are washed, scanned, dried and weighted. Win-RHIZO system is used to analyze the different morphological characters of root samples. Then, the indexes of roots per unit soil volume are calculated as root biomass (gm~3), root length (mm'3) , root surface area (m -m"3) , root volume (cm3-m~3) and fine root tips (tipsm"3) .Five physical indices of dominant Pinus massoniana, including root biomass, root length, root surface area, root volume and fine root tips, are analyzed and compared, it is found: The variable rule of five indexes is almost keep a identity, the root distribution of different diameters is plentiful in the extent of 40cm depth of soil layer, and it is gradually reduced to zero at deeper 40cm;Fine root main distribution is 0~~60cm depth of soil layer, and accounts to 92.9% of its total. The root of Pinus massoniana has a characteristic with deep root, but it is disadvantage to keep the tree body's balance for abundant root" distributing at 40cm depth of soil layer. Fine root biomass and others' four physical indexes are gradually reduced with the larger and larger distance from sample tree, and it is reduced to least at the position of 2.0m distance from Pinus massoniana, but they are increasing little by little at the position of excess 2.0m distance.The present stage productivity of the community is lower and its structure is irrational. The forest-type of the forest community and productivity structure of tree layer should be regulated so as to improve the integrate effects of the community. |
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