Forest ecosystems cover large parts of the terrestrial land surface and are major components of the terrestrial carbon (C) cycle. Most important, forest ecosystems accumulate organic compounds with long C residence times in vegetation, detritus and, in particular, the soil by the process of C sequestration. Trees, the major components of forests, absorb large amounts of atmospheric carbon dioxide (CO2) by photosynthesis, and forests return an almost equal amount to the atmosphere by auto- and heterotrophic respiration. However, a small fraction of C remaining in forests continuously accumulates in vegetation, detritus, and soil. Thus, undisturbed forest ecosystems are important global C sinks
