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)

Context Information about variations in basic density (BD) and carbon content (%C) along tree stems is key to assessing forest carbon sinks. Aims 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 ). Methods Twenty trees were felled in northern Spain, and 317 discs cut from the trees were dried and analysed to determine %C and BD. Results 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. Conclusion More accurate estimates of carbon contents were obtained by using specific values for different heights and anatomical parts, than by using single values.