| Schima superba is evergreen tree species in subtropical region of China, and often planted as a pioneer tree for the poor soil resistance and wide ecological niche. Because of its excellent resistance to fire, S. superba is often used in the firebreak forest. Therefore, S. superba has big potential as plantation tree. At present, researches about productivity and economic benefit evaluation of S. superba plantation were relatively less. Based in48a S. superba plantation in Nanning region, the biomass, productivity, distribution pattern, growth regularity and economic benefit of S. superba were researched by using a Quadrat method. The result will provide scientific evidence for productivity/benefit evaluation of S. superba plantation. The main results were as follows:(1) The total biomass of48a S. superba plantation is281.78t·hm-2, in which arborescent stratum is268.70t·hm-2(95.36%). Biomass allocation patterns of S. superba organs were:trunk>rhizome>bark>branches>thick roots>leaves>middle-size roots> rootlets. Distribution patterns of S. superba biomass according to diameter ranks were:20-24cm>16-20cm>24-28cm>12-16cm>28-32cm>abobe32cm>below12cm, and the biomass of abobe19.85cm average DBH trees (diameter at breast height) is185.57t·hm-2, accounting for69.06%of the total biomass of arborescent stratum. The total productivity of48a S. superba plantation is7.89t·hm-2·a-1, in which arborescent stratum is7.77t· hm-2·a-1.(2) Average tree height of48a S. superba plantation is22.79m, average DBH is19.85cm, and average volume is0.3398m3. The curve of current annual volume increment fluctuatingly rises, the maximum value of average tree height increment is0.58m in14a-16a stage, the maximum value of average DBH growth volume is0.54cm in10a-12a stage. The breast-height form factors of S. superba trees in48a plantation display the anteriorly rapid and posteriorly slow decline:2a-6a is1.05-3.32,8a-10a is0.55-0.69,12a-34a is0.50-0.52, and36a-48a is0.48-0.49. This suggested the straight stem form and the characteristic of early fast growth and long-term sustainable growth, qualifing for cultivation requirements of big-diameter trees. The result of model fitting among tree height, DBH and volume showed that tree measurement factor has a great relevance with stand age. The optimal model of tree height is quadratic curve model, optimal model of DBH and volume is Weibull model, and volume mathematical model can be used to accurately estimate volume of posterior S. superba plantation.(3) The average sale income of48a S. superba plantation is184566Yuan·hm-2, silviculture cost is58997.7Yuan·hm-2, and net profit is125568.3Yuan·hm-2. The biggest factor influencing economic benefit of48a S. superba plantation is timber price, the secondary factor is investment cost, and the smallest factor is output volume. The analytical result showed the market critical prices of log and fuelwood from S. superba plantation are270.91Yuan·m-3and125Yuan·m-3, while the current market prices are3.0times and2.4times of market critical prices, respectively, and the prices still have a rising trend in futre. Therefore, the S. superba afforestation project has a large profit space and a long-term profit period, and displays a strong long-term investment potential. |
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