An Early Study On Biomass And Chemical Characteristics Of Two Poplar Energy Plantations

Short rotation coppice culture systems are characterized by a high stool and shoot density, and by rotation durations between 2 and 3 years for species showing an extremely fast growth such as poplar. Differences in bark and wood content in woody biomass directly affect its quality and economic value as an energy source. In order to estimate the quality of biomass before harvesting, an allometric regression of bark percentage of total aboveground biomass and D22 (diameter at 22cm height) was developed. An allometric regression of total aboveground biomass and D22 was also maded to estimate the biomass production.What’s more, chemical composition of biomass at stand level could be estimated based on chemical traits of stem cross-sections and distribution of diameter classes within the whole plantation Two poplar short-rotation coppice systems, triploid Populus tomentosa B301 ((P. tomentosa×P. bolleana)×P. tomentosa) plantation and Populus×euramericana cv.’74/76’ plantation, were compared in terms of biomass yield and chemical composition. The main results were as followed:(1) A single general allometric equation linking shoot diameter to shoot biomass may be possible to be used to estimate biomass production for the two years,1 year after planting and 1 year after coppicing. Exception found for the two years and for triploid Populus tomentosa B301 plantation was y=0.0766x2.6102(R2=0.9636), and exception found for the two years and for Populus×euramericana cv.’74/76’ was y=0.0585x2.644 (R2=0.9538).(2) The stand biomass of 1 year after coppicing incressed as the planting density incressing. No significant difference was found in Populus×euramericana cv.’74/76’ plantation, which the biggest number occurred in density of 20000 plants/hm2(12.40 t/hm2) and the smallest one happened in density of 5000 plants/hm2(9.60 t/hm2). But, the stand biomass of triploid Populus tomentosa B301 under the density of 5000 plants/hm2 was significantly lower than the other two densities, which was only 6.54 t/hm2.(3) The stand biomass of Populus x euramericana cv.’74/76’and triploid Populus tomentosa B301 plantation in 1 year after coppicing was significantly higher than the year after planting. The stand biomass of Populus x euramericana cv.’74/76’in the year after coppicing under the density of 5000 plants/hm2,10000 plants/hm2 and 20000 plants/hm2 was about 10,6 and 4 times higher than that in the year after planting. While the stand biomass of triploid Populus tomentosa B301 in the year after coppicing under the same three planting densities was about 8,7 and 4 times higher than that in the year after planting. The stand biomass of the two plantations was about 6.54～12.40 t/(hm2·a), reaching the world-class level. More importantly, the stand bark biomass of the year after coppicing under the 3 planting densities showed no significant difference with that in the year after planting.(4) The chemical characteristics of three planting densities for Populus x euramericana cv.’74/76’and triploid Populus tomentosa B301 plantation after coppicing were almost the same. Cellulose, hemicellulose and lignin share of triploid Populus tomentosa B301 was 42.93%,20.85% and 27.69% respectively. Similarly, cellulose, hemicellulose and lignin share of Populus x euramericana cv.’74/76’plantation was 40.03%,20.57% and 27.86%.