The residence time of carbon is a major determiner of the capacity of an ecosystem to function as a source or sink of carbon. Recent studies of primary forest structure and dynamics have demonstrated differences in carbon use efficiency and growth rates for tropical forests from different regions of the Amazon. The overall residence time of carbon in primary forests is determined by (1) what fraction of photosynthetic products get respired quickly and (2) the residence time of C allocated to leaf (2-3 years), fine root (3-10 years), and stem (40-80 years) tissues, and (3) the time each of these components takes to decay, including what fraction is oxidized to CO2 versus what becomes stabilized in soil organic matter. Pasture and agricultural systems clearly have shorter ecosystem residence times than the forests they have replaced because they lack woody biomass, while secondary forests recover function belowground faster than aboveground. While biomass recovery in logged forests can be rapid, slow growth rates of individual tree species means that diversity will not recover in less than centuries.
Submetido por Susan E. Trumbore em 15-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)