© 1952 by Institute of Chartered Foresters
A STUDY OF GROWTH RINGS IN TREES
PART II. A Ring Pattern in European Larch
University College of North Wales Bangor
Errors and difficulties in counting the rings on larch butts (Larix decidua Mill.) in the Bristol region during a war-time survey led to an unsuccessful attempt to establish a pattern by the method of measuring ring-widths discussed in Part I. During this work it was found possible to recognize the ring-sequences by means of the pattern of light and dark zones in the growth layers. Two sorts of zones of denser wood were distinguished: the annual band of summer wood ending on the autumn break, here called the ‘autumn band’, and additional zones having their outer margins within the annual increment, found in 41 per cent, of the rings examined, and here referred to as ‘lines’. The width of the ring also was found to be of some help although in plantation trees it is subject to great interference from the effects of competition and management. A high degree of certainty in recognition and dating of the rings was found possible with the aid of these characters, especially the ‘lines’, many of which were found with great regularity in the same locus in the ring-sequence. A frequency diagram based upon ‘lineplots’ of 105 butts is presented, and four plates of photographs showing features of the pattern from different places. Examples are given and discussed of the differences in the pattern between different districts within about 50 miles of Bristol, between different sites in the same district, and between different trees on the same site. There were indications that ‘line’ frequency may tend to increase with the age and hardness of the rocks, provided suppression of the rings is not severe. Very young trees have an exaggerated tendency to ‘line’ formation, and the pattern is best shown in larch from about the sixth to the thirtieth year of growth. A few sections from other parts of Great Britain (Durham, Kent, North Wales) do not show the pattern in typical form although some features of it are present, and it seems likely that several regional patterns may cover the British Isles. If they have any common basis it must be looked for on very broad lines. The Bristol region pattern in Japanese larch {Larix Uptolepis Gord.) resembles that in European, but the few sections of other conifers examined present a somewhat different picture. The chief value of the pattern is considered to be that it increases ease and accuracy in the identification of the annual ring, and some practical applications are suggested.