Variation of certain chemical properties within the stemwood of black locust (Robinia pseudoacacia L.)

From the bottom, middle, and top of three mature 35 to 37-year old black locust tree discs were cut and analysed to determine the variation within the stem of certain chemical properties. Hot-water extractive content was greater in heartwood than in sap wood, while the reverse occurred for the dichloromethane extractive content. Vertical stem analysis of hot-water extractives showed that they increased in heartwood but decreased in sapwood from the bottom to the top of the stems while the reversal Occurred for dichloromethane extractive content of sapwood. At the bottom and the middle of the steins, ash content was greater in sapwood than in heartwood, but at the top no difference was found between heartwood and sapwood. Ash content of both heartwood and sapwood was found to increase in the axial direction with respective values of 0.36% (bottom) and 0.76% (top) for heartwood and of 0.65% (bottom) and 0.76% (top) for sapwood. Ash analysis showed that considerable variations were found for the inorganic elements K and P being greater in sapwood than in heartwood. Heartwood was more acid than sapwood except for the top of the steins. Acidity mean values were found to increase from the bottom to the top of the stems in heartwood while they slightly decreased in sapwood. Total buffering capacity of heartwood was greater than that of sapwood and total buffering capacity of sapwood exhibited an inverse relationship to height. Very small acid equivalent values were determined only in sapwood. At the bottom, lignin content in heartwood (25.73%) was greater than in sapwood (18.13%). Lignin content of heartwood decreased from 25.73% at the bottom to 18.33% at the top, while that of sapwood was 18.13% at the bottom. 21.42% at the middle and 19.64% at the top.