Long-Term Sustainability of Tree Energy Crop Carbon Storing in Soils:   It is well established in atmospheric sciences that soils can store only a given maximum level of organic carbon. At this maximum saturation point, the soil carbon will reach an equilibrium with the atmosphere and be returning as much carbon as it is taking in. However, the length of time it would take for any ecosystem to reach a maximum saturation level of carbon is highly dependent on a myriad of site specific factors such as initial soil quality, carbon content, sand, silt, clay content, climate, and rainfall.
According to numerous science-based studies, estimates for the length of time before the saturation effect occurs on short rotation woody biomass crop sites may be 75 to 100 years.
We often hear the misperception that the carbon sequestration/storing effect of growing tree energy crops is temporary.
Such a belief is clearly not based on established sound science. Although the maximum carbon level for any site is fixed, when carbon is stored in the ground it will stay there. It is just that forestry management practices can be implemented for perhaps 75 to 100 years before a maximum saturation level is realized. After this point, the site will be in equilibrium.
Carbon Levels on Environmentally Damaged Lands:   Thus, all carbon sequestration/storing that raises initial site organic carbon levels to the fixed saturation point is permanent. This point is especially relevant to environmentally damaged lands, such as growing tree energy crops on thousands of acres of closed phosphate mining sites in central Florida. Prior to phosphate mining, these sites were in various stages of native habitat/ecosystems for thousands of years (probably reaching a carbon saturation equilibrium).
After the cessation of mining activities, the soils had been altered from “native soils” to a soil type heavy in phosphatic clays. As a result of changing the soil type from mining activities, many of these sites have been overtaken by cogongrass (according to the U.S. Department of Agriculture, one of the most highly invasive, non-native noxious weed in the world) -- creating a prairie of weeds where native hammocks existed prior to mining. One of the surprising soil condition observations at the Common Purpose/UF tree plantation is that even though phosphate mining activities ceased over 50 years ago, there has been almost non-existent organic buildup in the heavy clay soils over this period.
Energy Crops as a Major Strategic Tool to Combat Global Warming.   By growing energy crop trees on environmentally damaged lands, a permanent carbon sink can be created:
Raising the very low levels of organic carbon in damaged soils.
To the point of maxium carbon saturation/equilibrium.