Carbon storage and recycling in short-rotation energy crops

Short-rotation energy crops can play a significant role in storing carbon compared to the agricultural land uses they would displace. However, the benefits from these plantations in avoiding further use of fossil fuels and in taking pressure off native forests for energy uses provides longer term carbon benefits than the plantation carbon sequestration itself. The fast growth and harvest frequency of plantations tends to limit the amount of above- and below-ground carbon storage in them. The primary components of plantation carbon sequestering compared to sustained agricultural practices involve above ground wood, possible increased soil carbon, litter layer formation, and increased root biomass. On the average, short-rotation plantations in total may increase carbon inventories by about 10 to 40 tonnes per hectare over about a 20 to 50 year period when displacing cropland. This is about doubling in storage over cropland and about one-half the storage in human-impacted forests. The sequestration benefit of wood energy crops over cropland would be negated in about 75 to 100 years by the use of fossil fuels to tend the plantations and handle biomass. Plantation interactions with other land uses and total landscape carbon inventory is important in assessing the relative role plantations play in terestrial and atmospheric carbon dynamics. It is speculated that plantations, when viewed in this context, could generate a global levelling of net carbon emissions for approximately 10 to 20 years. 16 refs., 7 figs