Study On Energy Structure Features Of Eucalyptus Plantations And Species Selection For Eucalyptus Energy Forest

In this paper the growth,biomass,calorific value and energy were studied for different ages, different species and different densities of Eucalyptus plantation in south China,and sumed up the energy structure features of Eucalyptus plantations;The indexes of combustion characteristics,the composition of the main substances and the main elements of some materials were analysed,? and the correlation between energy properties and material components were established; 2-4 Eucalyptus species for energy forest were obtained for the local by the comprehensive analysing on Eucalyptus species or clones. This study is helpful to provide basic data for comprehensive understanding of Eucalyptus stand characteristics and productivity, and to provide data support for the research of energy flow and material cycling of Eucalyptus plantation ecosystem in southern China, and to provide the oretical basis for more in-depth study of caloric value variation and also technical guidance for the development of Eucalyptus energy forest.(1)The variation of ash content (AC) and calorific value of various organs with stand ages were not different in two places had three Eucalyptus species. The average AC, gross caloric value(GCV) and ash free caloric value(AFCV) were little different among different Eucalyptus individual. The E.smithii platation increased 414.59 GJ·hm^-2·a-1 at the 6th year at which year it increased most among 2-6year; The mean annual increment of the total energy of plantation of E.leizhouensis No.1 and E.urophylla×E.grandis were maximum in 3.5-year-old among 1-4.5 year, respectively were 387.74 GJ·hm^-2·a-1 and 410.35 GJ·hm^-2·a-1. As a conclusion, the best time for harvesting of the energy plantation of E.smithii was 6 years and other two Eucalyptus were less than 3.5 years if in the only point of biomass and energy and despite the economic inputs and outputs and other factors.(2)The effects of density on diameter at breast height (DBH) and height (HT) were significant, and which stand volumes were different at different development stages. The individual biomass was decreased with increment of density. The stand volume and biomass in 1-year-old were biggest at density of 10000 ind·hm^-2 for 52.57 m3·hm^-2 and 32.02 t·hm^-2, respectively, and which those in 2-year-old were biggest at 2500 ind·hm^-2 for 75.85 m3·hm^-2 and 45.66 t·hm^-2, respectively. The effects of densities on wood calorific values and ash contents were not different significantly. It suggested that the optimal densities for Eucalyptus plantations at 1- and 2-year-old were 10000 and 2500 ind·hm^-2, respectively. (3) The 5 Eucalyptus by decreasing order of total biomass of plantation were: E. urophylla×E.tereticornis(161.60 t·hm^-2)>E.grandis×E.urophylla(127.96 t·hm^-2)>E. urophylla (112.60 t·hm^-2)>E.camaldulensis(83.81 t·hm^-2)>E.Leizhou No.1(71.36 t·hm^-2) in Shi Ling forest farm of Leizhou Forestry Bureau, Guangdong province.The decreasing order of total energy of plantation were the same as the order of biomass by reason of the average GCV were little different among different Eucalyptus individual. The average AC of 5 Eucalyptus were 1.40%～3.23% in Zhangmutou forest farm, Dongguan City, Guangdong province.And the average GCV and AFCV respectively were 16.76～17.81 kJ·g-1 and 17.30～18.13 kJ·g-1, the decreasing order of GCV and AFCV of individual respectively were: E.grandis=E.saligna> E.pellita>E.cloeziana>E.torelliana, E.grandis>E.pellita>E.saligna>E. cloeziana>E.torelliana.(4)The indexes of crude fiber, crude protein, crude fat, total N and also AC, GCV were significantly correlation with AFCV in the all indexes of combustion characteristics, the composition of the main substances and the main elements for the trunk of 5 Eucalyptus and various organs of E.grandis×E.urophylla.?(5)The result of cluster analyzing for AC, and GCV of 5 Eucalyptus in Zhangmutou forest farm showed that E.grandis, E.saligna and E.pellita could be clustered one type as they had higher GCV and lower AC than other 2 Eucalyptus. And E.grandis, E.saligna and E.pellita were more suitable for Eucalyptus energy forest as they were more in line with the characteristics of low AC and high GCV than E. cloeziana and E.torelliana judged by the results of research.(6)The result of factor analysis for the indexes of biomass, calorific value, the composition of the main substances and the main elements of 5 Eucalyptus in Shiling forest farm showed that E. urophylla×E.tereticornis and E.grandis×E.urophylla were suitable for Eucalyptus energy forest, followed by E.urophylla, E.camaldulensis and E.Leizhou No.1 were not suitable as species for energy forest.The 4 method which were GCV, energy, the factor analysis and Ligaoyang and other's avaluation were used for judging the 5 Eucalyptus were suitable or not for energy forest and which were suitable, which showed that the result of method of evaluated by GCV were different with other 3 methods, while the results of other 3 methods of evaluation were almost the same.(7) The indexes of growth, biomass and carbonization and other indexes of 11 Eucalyptus clone in South China Experiment Nursery were analysed by the method of principal component analysis, and the decreasing order of final score were G₄>LH₅>G₉>DH₃₂₂₂>LH₁>EC₃₄> DH_201-2>M₁>. The result of the cluster analysis showed that G₄, LH₅, G₉ and DH₃₂₂₂ were clustered one type which could be suitable for energy forest, LH₁,EC₃₄, DH_201-2 and M₁₄ were clustered one type which had lower potential as species for energy forest; E.Lauan No.1, UC_184-1, and SH₇ were clustered one type which were not suitable for energy forest.