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

Abstract

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. The biomass of 9a, 15a, 26a and 34a stands were 61.67, 123.57, 171.58, 203.01 t/ha, and the total energy of them were 11.92, 24.28, 33.37, 39.68 × 108 kJ/ha, respectively. The biomass and energy of the tree layer accounted for 90% of the total stand and were greatest in stemwood, which can be simulated by Logistic models, and reached biomass and energy maturity at about 35 years. The results not only be helpful for the decision makers to efficiently obtain more biomass with high energy, but also enrich the content of energy ecology.