A Study On The Biomass And Productivity Of Acacia Spp. Plantation On Minnan Mountain

Acacia spp .were introduced to china in 1960s, which have been showed good adaptability and high productivity. As a kind of important short-cycle industrial raw material forest tree species, of which has being provided advantage with good adaptability and wood property, high production, and the most it has the root bacterium that has the capacity to improve the N circulating in the soil. With the abundance of litter fall, the surface run-off and the momentum of rainfall has been retained, minimal the scale of soil erosion. From all the bioecological characteristics of the Acacia spp . we can concluded that it benefit to maintain the productivity and the sustainable use of the woodland .Explore the biomass and productivity of Acacia spp . tabulaeformis to make sure the utilization of nature productivity and blanced the plant community productivity . At present ,the majority researches were focurs on forest introduction,selection,pest control,ecophysiological,bioecological characteristics and forest Productivity and so on. But the researches on forest biomass and productivity were mostly centralized on the above-ground. This research was carried out an systemic discussion on the biomass and productivity. From comparative analysis the three groups of Acacia spp. We can give a basic theory of restoration and reconstruction for degraded ecosystem and so on.The experiment began in July 2006 at the Tianma forest farm in ZhangZhou , FuJian, where is the natural distribution of Acacia spp . In the recent years, the farm introduced A. mangium, A. melanoxylon, A. plectocarpa which were showed good adation to the climate. This experiment was focus on Acacia spp.(A. mangium, A. melanoxylon, A. plectocarpa) which were planted on the one side grade of the mountain. It was explored the relationship of DBH, height and production of organ above the ground form standard trees, the biomass accumulation and distribution and the NPP of Acacia forest in three groups. From the results ,we can conclusion that:1,The results of the fund and distribution in the stands of Acacia spp show that The production in A. mangium plantation stand is 162．7t/hm²(six-year old), of which the tree layer is 153．59t/hm², accounts for 94．40 percent. the shrub is 1．00t/hm², accounts for 0．6%. the herb is 4．75t/hm² and the litter layer is 3．36t/hm², the proportion of biomass is 2．91% in shrub and 2．04% in herb. The production in A. melanoxylon stand is 135．65t/hm², of which the tree lawyer accounts for 96．27 percent, the shrub 0．98%, the herb 0．34% and the litter lawyer 2．40% with 3．25t/hm²ï¼ŽThe production in A. plectocarpa stand is 161．49 t/hm², of which the tree layer occupies 95．00% and the plant under-stand and the litter lawyer 5．00%.2,Using the data such as DBH, height and production of organ above the ground form standard trees and through the relative growth formula of W=aD^b and W=a (D²H)^b can set up the regression equation correlating those three parameters. The results were reported as follows. The determination coefficients were high both in these two formula. The highest is 0．840 while the most are more than 0．96, which indicated an obvious correlation and can apply to the production of tree lawyer.3,The study on the formed tree's accumulation and distribution of Acacia spp. show that tendency of distribution is same in 3 tree layer. The stem's biomass in 3 tree layer. The arrange of the organs' biomass by quantity is stem, branch, leaf and bark. The stem's biomass account for the 60%, and the root 10%. With the tree's height rise, the quantity of biomass of stem and bark descent gradually. On the other hand, the quantity of leaf and branch rise with it. The shape of tendency of stem and bark is singlet pole. Leaf and branch' quantity shape is normal distribution. The root system's distribution density change trend is similitude with above-ground. With the depth arise of soil layer, the fine roots descent sharply. The trend of root descent smooth out.4,The Analysize of plant biodiversity and similarities in Acacia forest show that the diversity indicator of Shannon-Wiener in A. mangium plantation was largest, followed by A. melanoxylon stand, A. plectocarpa stand smallest. However, the evenness indicator irrelevant with species was largest in A. melanoxylon stand which demonstrated that the more even species composition is, the smaller the gap is. Although these three different species at the same hill side and the small difference altitude, the similarity indicator is between 0．5 and 0．75 as medium similarity due to the different affects form different species to habitat.5,In the Acacia plantations, net productivity calculates from annual mean net production. In the A. mangium plantations, annual mean net productivity is 26．557t/hm^-2 a^-1 , and the tree lawyer occupies 25．593% while the shrub lawyer and the herb lawyer is 0．1667t/hm^-2 a^-1 and 0．792t/hm^-2 a^-1 . In the A. melanoxylon forest, annual mean net productivity of the tree lawyer is 21．767t/hm^-2 a^-1 , while the shrub lawyer and the herb lawyer are 0．222t/hm^-2 a^-1 and 0．078t/hm^-2 a^-1 . In the A. plectocarpa forest,annual mean net productivity of the tree lawyer is 26．915t/hm^-2 a^-1 , while the shrub lawyer and the herb lawyer are 0．272t^*hm^-2 a^-1 and 0．333t/hm^-2 a^-1 .Among the three Acacia plantations, the A. plectocarpa forest has highest annual mean net productivity of 27．52t/hm^-2 a^-1 , followed by the A. mangium plantations, and the A. melanoxylon forest lowest of 22．067 t/hm^-2 a^-1 .