Studies On The Biomass And Calorific Value Of Eucalyptus With Various High Densities

As one kind of biomass energy, energy-forest has long been popular in the world. Therewere much more researches in energy-forest with low densities but super high densities. In thisstudy, biomass、calorific value and the ages at quantitative maturity were studied based oneucalyptus with9different super high densities.(1) Stands of1year old DH32-29eucalypt clone with nine different densities forenergy-forest were investigated. Growth, biomass and calorific value of different organs fromtheir stands were analyzed; the results showed that effect of nine different densities on heightgrowth and stem base diameter was obvious；biomass of leaf and stem decreased as the standdensity increased；The individual plant biomass decreased with density increasing while standbiomass was on the contrary.(2) The results showed that effect of nine different densities on the individual averageGCV、forest total average GCV and ash contents was obvious; The individual averageGCV andash contents among the densities of M156、M254、M204、and M154had no significantdifference. However as the stand density increased, the differences of individual ash contentsand GCV between stands with high density and low density reached significant level. However,the forest total GCV increased with densities increasing.(3) According to the annual economic benefit analysis of energy-forest with differentdensities, the results showed that it was detrimental to profit if the densities is too high or toolow, The spacing of M254and M156had no revenue because of low biomass and The spacingof M152was not profitable because of the high cost of seeding and labor, The ranking of otherspacing were M202>M154>M204>M252.(4) the results showed that the biomass of stands increased as the stand density increasedand its differences between stands with high density and low density reached significant levelin each month in the first year; The influence of row spacing on the stand biomass was largerthan the line spacing in the early growth while the situation was on the contrary after the stand was closed; The ages at quantitative maturity of spacing M156、M204、M252、M244、M2524were11months, the M152and M254were12months while M154and M202needed13months to be mature.(5) Topdressing experiment with DH3229eucalypt clone at Suixi County,southGuangdong,was conducted in February of2012.The topdressing was designed at2levels,2treatments and3repeats by random block arrangement, trees without topdressing was thecontrol. Growth, biomass and calorific value of different organs from their stands wereanalyzed in June of2012; the results showed that the effect of topdressing on height growth ofthree different densities was not obvious while topdressing had an extremely negative impacton the growth of diameter at stem base, and it affected the stem base diameter significantly;biomass of leaf, branch and stem decreased as the quantity of fertilizer increased; Theindividual plant biomass and stand biomass increased with quantity of fertilizer increasing; Theindividual average GCV and ash contents among the different kinds of fertilizing methods hadsignificant difference, the topdressing method F2had the highest individual average GCV andits ash content also lower than control. So the total evaluation on all the indexes indicated thatthe topdressing method F2was chosen to be the best choice for the energy sources forest ofshort cycle eucalyptus with super-density.