Carbon stock changes in successive rotations of Chinese fir (Cunninghamia lanceolata (lamb) hook) plantations

Chinese fir is an important timber species in Southern China. Millions of hectares of Chinese fir plantations have been established during the past decades, and increasing areas are re-planted as second or later rotations. Since the 1980s, scientists and forest managers have reported apparent yield decline and soil fertility degradation over successive rotations. If this yield decline is accompanied by a reduction in carbon stocks, and if it is caused by management, it has to be considered as a form of forest degradation and will become important from a carbon-accounting point of view. In this paper we have collected and compiled published data relevant to growth and soil properties over successive rotations of Chinese fir, calculated the stocks of stand biomass and soil organic carbon and nitrogen, and have analyzed the impact on carbon stocks of growing Chinese fir over successive rotations. We found that on an average, stand biomass increments were reduced by 24% from the first to the second rotation, and by a further 40% from the second to the third rotation. Soil organic carbon was reduced by 10% and 15% between the first and second, and second and third rotations, respectively. Soil carbon losses were usually accompanied by nitrogen losses but carbon losses were generally larger than nitrogen losses. The reduction of carbon stocks in successive rotations appears to be related to increases in soil bulk density and nutrient losses caused by burning of residues during site preparation. Potential afforestation/reforestation projects under the clean development mechanism (CDM) of the Kyoto Protocol may also need to consider the possible yield decline and soil degradation over successive rotations of plantations. (C) 2004 Elsevier B.V. All rights reserved.