Estimating Carbon Sequestration Rates on a Regional Scale

In earlier chapters, especially Chapter 11, we discussed the accumulation and stability of humus on single plots and in single stands. We discussed the transition from the fraction of litter that we considered stable, to a developed humus layer. In our examples, we used the limit value for one main litter type, viz. foliar litter, to calculate amounts of humus. It is evident that the stable humus layers are built up from several litter components in addition to foliar litter from trees, although the foliar component normally is the dominant one. Ideally, we should have used limit values from a whole set of litter components, at least the major ones, and added stable fractions for litter components such as leaf litter from ground vegetation, from moss, and from other tree litter components such as cones and woody material, e.g., twigs. We can make the list even longer and for a proper quantification, this is evident. Unfortunately, the available information to do this is lacking. The only litter component for which there exists reasonable information is the foliar one, both as regards litter production and the decomposition process. We have discussed the possible formation of stable humus from other litter components, and we cannot exclude that, e.g., woody litter may produce only a small fraction.