Number of cells in xylem, phloem and dormant cambium in Silver fir (Abies alba), in trees of different vitality

We investigated the anatomical structure of phloem and xylem growth rings as well as the dormant cambium in relation to vitality in 81 adult silver fir trees (Abies alba Mill.). Specifically, we investigated the number of cells produced in the current phloem growth ring (PR), xylem growth ring (XR) and their ratio, the number of cells in the dormant cambium (CC), and the structure of the PR, which included characterisation of the early phloem (EP), the late phloem (LP), and the presence, absence, and continuity of tangential bands of axial parenchyma (AP). EP was relatively stable with respect to number and types of cells as PR width changed, but LP was quite variable. The CC of more vital trees produced more xylem than phloem cells. The ratio of XR to PR number decreased with decreasing vitality of trees and in the most severely affected trees (4% of the study group), more cells were formed in the PR than in the XR. The number of cells in phloem, xylem and dormant cambium is positively correlated. The use of width and structure of phloem and the ratios between PR, XR and CC can provide information on tree conditions and, consequently, can be a useful tool for forest management