Thermal analysis of earlywood and latewood of larch (Larix gmelinii (Rupr.) Rupr.) found along the Polar tree line

摘要

This paper deals with the results of a study of the thermodestruction of the earlywood and latewood in the 1988-1998 growth rings of Gmelin larch (Larix gmelinii (Rupr.) Rupr.) trees growing along the polar tree line (70(A)52'53aEuro(3)N, 102A degrees 58'26aEuro(3)E, Taimyr Peninsula). The study used methods of thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC). Thermogravimetric data obtained were analyzed by Ozawa-Flynn-Wall kinetic model. We determined macrokinetic parameters of thermodestruction. Earlywood and latewood showed no significant difference in cellulose/hemicellulose/lignin ratio, whereas they differed significantly in destruction average value of activation energy (197.55 and 55.90 kJ mol(-1), respectively). Our analysis of the correlation of thermodestruction values with mean monthly air temperature and precipitation revealed that component composition of both earlywood and latewood was influenced more by the weather conditions at the beginning of the growing season (April-June). Air temperature had markable influence on the wood component composition during cell wall synthesis only in latewood, whereas precipitation influenced the composition in both latewood and earlywood. TG/DTG and DSC methods were found to be promising for developing information on biochemical composition of early and latewood tracheids in stems and for identifying the extent of the influence of climatic changes on cell wall synthesis.