Comparison of radial increment and volume growth in stems and roots of Quercus petraea

Dendrochronological studies dealing with roots, stems and branches are very rare or often take the form of short notes. The difficulties of detecting rings and of quantifying the radial growth in roots have already been descr ibed for various species. In oak the anatomical root structure differs from stemwood. The roots are radial-porous or diffuse-porous, and there is ofte n no clear distinction between individual rings. In our study visual and ra diographic techniques were used to examine radial increment in roots of ses sile oak (Quercus petraea L.) which was compared with radial growth in bran ches and along the stem. Coarse roots were cut from four 30- to 34-year-old trees that had been uprooted mechanically and disks were taken at differen t distances from the stem-root base. Ring widths were measured in the stem at height of 0.3 m, at breast height (1.3 m), beneath the crown, in branche s of the crown, and in roots every 20 cm. The ring widths were cross-dated, and the heterogeneity of growth within a root and within the root system w ere analysed. Asymmetric growth frequently occurred in roots so that ovals, I-beam and T-beam shapes were developed. With the method used in our study the annual growth layers close to the central cylinder could be distinguis hed as well as beneath the bark. Pointer years were detected in all section s of the tree and permitted correction of ring widths in roots. Root system , stem and branch showed a basic similarity in their radial sequence of rin g width. The annual biomass increment was weaker and more variable with sev eral consecutive changes in the roots than in the stems. The root/shoot rat io reached a minimum rather early, beginning at the cambial age of 20 years .