Szekessy Vilmos (szerk.): A Magyar Természettudományi Múzeum évkönyve 62. (Budapest 1970)
Kováts, D.: Quantitative xylotomic investigations on the xylem of our home ash trees
above statement, however, in 2 of the 5 trees the growth ring width increased, though with certain fluctuations, from the pith towards the bark (Fr. 5 and Fr. 32). According to SÁRKÁNY and STIEBER (1958), growth rings are wider in trees growing in moist substrates. I, too, experienced the same phenomenon: the European Ash marked Fr. 5 originated from a marshy wood in the Plains and its growth rings are the widest as compared to those of the other examined specimens (Figs. 1,2). It is a general trend that growth ring width shows a strong initial maximum and then decreases rather rapidly (SÁRKÁNY et STIEBER, 1958). This statement holds most distinctly for trees Fr. 9, Fr. 15, and Fr. 11/a, but not for Fr. 32 in which there occurs, after an initial decrease, a strong increase, again followed by a decrease and terminating in a maximum. Tree Fr. 5 displays the very opposite with its rather considerable rate of initial growth ring width increase and a final maximum (Figs. 1, 2). Taking into consideration the growth ring width, both in tension and pression woods, of all 5 trees, a decrease (minimum) appears between the years 1926-1930 and 1945-1948, while a growth ring width increase (maximum) is less manifest though still discernible in the tension wood between the years 1941-1943 (except for the tree Fr. 9, exhibiting some stagnation and minimum). Increase is still less unequivocal in pression wood in the respective years (Figs. 1, 2). Climatic factors also extensively affect changes in growth ring width (SÁRKÁNY et STIEBER, 1958). My research material originates from five different localities, obviously exposed to diverse local climatic conditions. This is w 7 hy the effects of the given year appear so heterogenous, even though the above (small-rate) homogeneities are present. The effects of the year on growth ring width is multiple and of diverse rates owing to the numerical relationship between growth ring width increase and decrease. The effects of a given year is seldom unequivocal (homogenous), indeed, there is none with respect to the combined tension and pression woods. We have attempted to express this heterogeneity by the following formula (STIEBERKOVÁTS) : where Q = the relation of growth ring width increase and decrease ; M = a greater number of cases of growth ring width increase or decrease in a given year; jn = a smaller number of cases of growth ring width increase or decrease in a given year. Changes in growth ring widths were in all cases related to the growth ring width data of the preceding year; x = M+m. Increases in growth ring width were regarded as positive (+), decreases as negative (—). The above formula is operative only by statistical data. Owing to the relatively small number of individuals, I refrain from submitting the statistical data and present the formula as merely a method considered applicable. The obtained data are plotted on the graph of Fig. 3. Unambiguous years for tension wood are 1929 (growth ring width increase, + homogeneity) and 1943 (growth ring width decrease, — homogeneity); for pression wood the years 1937 (growth ring width increase, 4- homogeneity) and 1939 (growth ring width decrease, — homogeneity).
