52 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



7. Observations on the Annual Increment of 

 Spruce and Scots Pine. 



By J. H. Milne-Home. 



During the growing season "of 1910 monthly observations 

 have been made of the increase in girth of certain selected 

 average trees in different plantations, and the results obtained 

 may perhaps be of interest. 



The increment measurements were taken by means of 

 malleable lead bands ^ inch in width, and about the thickness of 

 thin cardboard. The bands were attached to the trees by 

 means of L-shaped staples, one end of the band being made 

 fast, the other end remaining loose, and merely supported on the 

 staples. A vertical scratch with a knife at the exact point where 

 the loose end of the band overlapped the fast end, served to 

 indicate the starting-point of the season's growth, and the 

 gradually widening space as the stem expanded could then be 

 readily seen and measured. The observations were taken in 

 sixteenths of an inch, but in order to avoid fractions they have 

 been transposed in the table of results into decimals of an inch. 

 An identification number was put upon each band used. The 

 possibility of using Pressler's Increment Borer for making the 

 observations was considered, but discarded as unsuitable for 

 continuous observations on the same trees, more especially for 

 the monthly records. 



The three plantations regarding which particulars are given 

 are situated in the south-east of Dumfriesshire. 



Plantation K is 37 years of age, and was formed from poor 

 hill pasture. The ground slopes slightly to the south, and the 

 elevation is about 500 feet, in an exposed situation. The top 

 soil is about 9 inches in depth, consisting partly of peat and 

 partly of a poor yellowish sand, merging into a hard subsoil 

 of similar colour. The land is said to have been very wet when 

 planted, and the number of open drains confirms this. The soil 

 is now, however, fairly dry, wherever the leaf canopy is good. 

 The plantation is 36 acres in extent, consisting partly of Scots 

 pine almost pure — where the observations have been taken, — 

 partly of almost pure spruce, and partly of an admixture of the 

 two species. There is a sprinkling of larch, birch, alder and 

 oak throughout. The soil is manifestly much more suited to 

 spruce than Scots pine, and where a mixture occurs, the former 

 is rapidly suppressing the latter. 



