Geographical differences in the content of main chemical components in cork of Quercus variabilis

  Objective  This study aimed to analyze the main chemical constituents and environmental influencing factors of cork from Quercus variabilis through a wide range of samples in China, which would be helpful to provide scientific reference for the oriented selection and scientific utilization of cork resources.

  Method  Cork from Q. variabilis was collected from 12 regions in China for the determination of cork resin, lignin and other major chemical components, and the chemical components of cork from different locations were compared by LSD multiple comparison, principal component analysis and cluster analysis.

  Result  The average contents of main chemical constituents (the chemical composition content in this paper refers to the mass fraction) of the cork were: the total extractable matter was (13.94 ± 0.54)%, the suberin was (41.63 ± 1.44)% and the lignin was (23.03 ± 2.26)%. According to the content of suberin and lignin, the 12 provenances could be clustered into three groups, among which Lincheng (Hebei Province of northern China), Yongxiu (Jiangxi Province of eastern China), Jinzhai (Anhui Province of eastern China), Nanjing (Jiangsu Province of eastern China) and Neixiang (Henan Province of central China) had relatively high suberin content, while Jiyuan (Henan Province of central China), Meixian (Shaanxi Province of northwestern China) and Tianshui (Gansu Province of northwestern China) belong to the groups with high lignin content. The left provenances, Shangluo (Shaanxi Province of northwestern China), Chengbu (Hunan Province of southern China), Pinggu (Beijing of northern China) and Tianlin (Guangxi of southern China) belong to the middle group. The correlation analysis showed that the content of dichloromethane extract and total extractable matter was negatively correlated with latitude, while the suberin content increased with longitude and soil nitrogen content. The annual mean temperature had little effect on chemical composition content, but mean annual precipitation had significant positive correlation with the suberin, the dichloromethane extract and total extractable content.

  Conclusion  On the whole, there are certain geographical differences in the chemical composition content of cork from Quercus variabilis in China, and they are mainly affected by latitude, mean annual precipitation, and soil nitrogen content.