Rainfall a Factor of Tree Increment. 225 



The above sections which were obtained through the courtesy 

 of Dr. Britton, Director-in-Chief of the New York Botanical 

 Gardens, show very clearly the retarding influence which the lack 

 of water has on tree growth. Sections B. G. i, 2, 4, 5 follow the 

 decrease in rainfall and lack of water very closely and the thick- 

 ness of the annual rings gradually gets less and less as the years 

 go by, a deficiency of rain being recorded since 1904, using the 

 seven complete records obtained since this station was established. 

 The deficiency indicated is obtained by comparing with the average 

 at adjacent stations. 



Section B. G. 3, 6 and 8 which do not react to the deficiency of 

 rain in 1908 do show a reaction during certain years of low rain- 

 fall ; 3 B. G. reacts until the last year, while 8 B. G. does not react 

 in 1906 and 1908. This tree, however, stood free in a very sunny 

 spot more or less protected from the northerly and westerly winds. 

 Measurements taken along one diameter show a decrease of 3/80 

 inch over 1907, while another shows an increase of only 1/40 inch, 

 and the third diameter gave an increase of 7/80 over 1907 and the 

 total average only shows an increase of 5/80. 



As this tree stood free and clear on the southerly side, the heat 

 of the sun was able to affect it and as the spring was fairly warm 

 and there was a gradual increase in temperature as summer ap- 

 proached in those years, it is to be expected that this would have 

 considerable effect upon the tree increment. 



Although the above results prove without doubt that the annual 

 growth of a tree is affected by the meteorological phenomena, 

 further samples were obtained in New Hampshire and Vermont. 

 The latter were four Norway Spruce growing on the Billing Farm 

 at Woodstock, Vermont. They were splendid healthy specimens 

 and were all cut in December, 1908. 



1 Vt. a thirty-two year old Norway Spruce growing alone on a 

 hill side (southerly exposure), exposed on all sides, fairly good 

 soil. 



2 Vt. a thirty-two year old Norway Spruce growing in a grove 

 planted twelve feet apart in a sandy soil with a gravelly sub-soil 

 located on a hill with a northerly exposure and taken from the 

 center of the grove. 



