Calorifc value variations in each component and biomass-based energy accumulation of red-heart Chinese fr plantations at different ages

Calorific values (CV) of plants plays a key role in energy conversion. The red-heart Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) is one of the most important commercial timber species in southern China. However, little is known about its CVs. We compared the CVs of C. lanceolata organs, understory, and litter from four different stand ages (9, 15, 26, and 34a). The results showed that the ash-free calorific value (AFCV) can more accurately reflect CV than gross calorific value (GCV). The AFCV of stemwood increased from the lower to upper, and was higher in heartwood than in sapwood. AFCV in organs increases with stand age and was the highest in leaves and lowest in bark. AFCV of litters also increased with stand age. But AFCV of understory reduced with increasing of stand age, and the AFCV of aboveground were higher than that of underground. Ash content (AC) of tree organs was not associated with GCV, but affected AFCV, observably.