Variation in carbon concentration and basic density along stems of sessile oak (Quercus petraea (Matt.) Liebl.) and Pyrenean oak (Quercus pyrenaica Willd.) in the Cantabrian Range (NW Spain)

Information about variations in basic density (BD) and carbon content (%C) along tree stems is key to assessing forest carbon sinks. The aim of the study was to determine any differences in %C and BD between different woody tissues (bark, sapwood and heartwood) in two widespread European oak species (Quercus pyrenaica and Quercus petraea). Twenty trees were felled in northern Spain, and 317 discs cut from the trees were dried and analysed to determine %C and BD. There were significant differences in %C between bark, heartwood and sapwood, and between species. There were also significant differences in BD between the tissues (heartwood > sapwood > bark), and the BD was higher in Q. petraea than in Q. pyrenaica. Both %C and BD varied along the stem. More accurate estimates of carbon contents were obtained by using specific values for different heights and anatomical parts, than by using single values.