Chemical Characteristics of Heartwood and Sapwood of Red-Heart Chinese Fir (Cunninghamia lanceolata)

Abstract

Abstract The chemical composition of wood is an important factor affecting the properties and utilization of wood. To compare the difference in chemical compositions between heartwood and sapwood of red-heart Chinese fir (Cunninghamia lanceolata), three graded wood, dominant, average, and overtopped trees were selected from the Chenshan Forest Station of Anfu County in Jiangxi Province. Their chemical composition parameters were determined according to international standards. Our results indicate that sapwood contains on average a higher moisture content than that of heartwood, constituting 9.4 and 8.6 percent, respectively. The pH values of wood present acidic and are higher in sapwood. Cellulose is abundant in both wood tissues; the heartwood content (52.0%) is higher than that of sapwood (48.6%) on average. Furthermore, the lignin in heartwood is slightly less than that of sapwood. Hemicellulose content is similar in heartwood and sapwood (23.4% vs. 23.1%), on average. All kinds of extractives in heartwood are substantially richer. Approximately three times more benzene–ethanol extractives are in heartwood than sapwood. This suggests that there is a considerable variation of chemical constituents among the graded woods (P < 0.05). The pH values are both significantly correlated with the contents of the four extractives in heartwood and sapwood (P < 0.05). The longitudinal variation of chemical compositions is different along the direction of tree height in heartwood and sapwood. Understanding the chemical heterogeneity of wood is vital for wood product manufacturing as well as for wood property improvement.