The Research On The Carbon Pools Of Ecological System Of Eucalyptus Grandis Plantation In Rare Earth Tailings Area

In recent years, with the increase demand of developing rare earth mineral in southern Jiang xi province, a large area of vegetation and the ecological environment were severely damaged, soil erosion aggravated, bedrock exposed, governance and recovery of the damaged vegetation is urgent.Eucalyptus was excellent timber forest with the characteristics of fast-growing, good resistance, excellent Barren resistance and extensive use. By Long period of exploration, we founded that Eucalyptus can grow on the soil of rare-earth tailings. As the one of few species which could survive on the soil of rare-earth tailings,It could not only played a role on vegetation restoration and ecological reconstruction in such area, but also could harvest lumber, green damaged mountain, fix CO2, form carbon pools through planting large area of Eucalyptus plantations. Forest carbon pools could effectively ease the global greenhouse effect. Therefore, it taked very vital significance to correct evaluated the forest ecological system carbon storage. The different tree ages of Eucalyptus grandis plantation which lived in the rare-earth tailings mining area of GanNan were researched in this study. The research content included the tree layer and the shrub layer, herb layer, falling object layer and soil layer carbon storage, as well as the evaluation of ecological system carbon function.At the same time, Labile organic carbon (soil microbial biomass carbon) was analyzed further. The main research results were as follows:(1)The biomass of different ages of Eucalyptus plantations in rare-earth tailings were in the sequence of2-year-old plantation (23.82t/hm2)>1-year-old plantation (23.02t/hm2)>1-year sprout plantation (20.88t/hm2). Between various organs of the tree layers, the average biomass of tree stems and branches was more than that of leaves and fine-roots. Between understory layers, the average biomass of the tree layer was the highest, followed by the litter layer. The Average biomass of shrubs and herbaceous biomass were extremely low. Due to the climate impact of Gannan, Eucalyptus grandis plantation prone to frost damage. Therefore, the organ biomass between different ages of Eucalyptus grandis plantations was no significant difference. Under the fost stress,1-year-old plantation and perennial plantation had the same greening effect. During The same tree age, the biomass between the various organs was significant difference. (2) The carbon content of different tree ages of Eucalyptus grandis plantation vegetation ranged in between0.4-0.5, the minimum value was less than the internationally recognized generic lowest value of0.45.Different organs of the average carbon content of the tree layer were in the sequence of stems> branches> leaves>fine-roots, and it related lignification levels. The average carbon content of understory layers were in the sequence of shrub layer> litter layer> herb layer. The difference of carbon content between the stand layers was significant difference. Because of Eucalyptus frequently subject to damage.the soil organic carbon content in the sample of the tailings mining area was relatively low. The average organic carbon content of0-20cm soil layer was0.35g/kg, while0.33g/kg in20-40cm soil layer. The organic carbon content of the upper and lower between different tree ages was no obvious pattern. soil organic carbon content of1-year sprout plantation was highest, and the soil fertility was higher than in the other two stands.(3)The carbon storage of eucalyptus plantation ecological system increased with the increase of tree ages, the carbon storage of1-year sprout plantation was the highest, reached13.37t/hm2, which indicated that could absorb a lot of carbon dioxide. Because of the soil of rare-earth tailings mining area was infertile, we investigate the fine-root in test range, so the carbon storage of soil layer was small. The average carbon storage of each layer in ecological system was in the sequence of Tree layer> soil layer> litter layer> shrub layer> herb layer, the ability of carbon fixation of soil layer was. inferior to tree layer.Because of the frequently frosts, the carbon storage in the same layer showed irregularity between different tree ages. The carbon storage of each layer in the same age of stand in Eucalyptus grandis plantation displayed a significant difference.(4)Soil microbial biomass carbon significant positive correlated with total organic carbon.It was more sensitive compared with soil total organic carbon because of the influence of various factors, therefore, the small changes of labile organic carbon content can accordingly cause the changes of soil total organic carbon content.To sum up, because of the soil of rare-earth tailings mining area was special, the tree layer played a decisive role in the carbon pools of ecological system and the carbon storage of every layers in forest ecosystem did not increased with the increase of tree ages due to frosting. But Eucalyptus grandis plantation had grater survival and competition ability compared with other species of the soil of rare-earth tailings mining area.Compared to as timber forests and economic forest, Eucalyptus grandis plantation was more suitable for one of the vegetation restoration as most pioneer species on rare-earth tailings mining area for ecological reconstruction and the carbon pools of ecological system.