WATER RELATIONS OF FOREST TREES 369 



rainfall and radial growth; rather, site conditions were of primary impor- 

 tance and Diller (1935) substantiated this conclusion by saying that soil 

 moisture observations were better than precipitation records since the 

 variable factors of run-off and seepage would be eHminated. Usually 

 drought affected growth of the following year, whereas in wet years 

 increase of growth occurred the same season. If trees are growing where 

 drought or soil wilting conditions may occur, there may be a direct cor- 

 relation of growth with precipitation. Bogue (1905) reported that this 

 occurred in sugar maple [Acer saccharum Marsh.) where the effect of ab- 

 normally large or small precipitation on radial growth is evidenced the 

 folio whig year. Lodewick (1930) also correlated ring width of the long- 

 leaf pine [Finns pahistris Mill.) in Florida with precipitation during the 

 March-October period. He indicated that vigorous trees were the best 

 indicators with dry years useful for cross-identification. Various tests for 

 rehabihty included the relative production of spring wood to summer 

 wood. 



The radial growth of short-leaf pine [Pinus cchinata Mill.) and white oak 

 [Quercus alba L.) was studied with a dial gauge dendrometer by Boggess 

 (1953) who followed soil moisture at different depths (down to 60 cm), 

 rainfall mside and outside of the stand, air and soil temperature as well as 

 evaporation. He found that both pine and oak completed 80% of their 

 basal growth by the end of June, when available moisture through the 

 profde became exhausted. The sporadic periods of diameter increase inter- 

 spersed with periods of stem shrinkage in the latter part of the growing 

 season were then directly related to the availabihty of soil moisture which 

 becomes a hmi ting factor in diameter growth during most seasons, although 

 other factors might affect the final cessation of growth (Boggess, 1956). 



In the relative utihsation of soil moisture by various species. Shear and 

 Stewart (1934) found that water was removed from the soil most rapidly 

 by all species, white pine excepted, at about the time new foHage is pro- 

 duced. Larch, white oak and white pine removed more water from the 

 first four feet of soil during the growing season than green ash [Fraxinus 

 pennsylvanica var. lanceolata (Borkh.) Sarg.) and silver maple [Acer sacchari- 

 num L.). Soil moisture was affected to a depth of three and a half metres 

 under white oak, three metres under larch, two and a half metres under 

 maple and white pine and two metres under green ash. The water table 

 fluctuated from about one metre dov^oi to these depths, thus the trees had a 

 constant source of water from the water table. 



Concerning the utihsation of soil water, Schopmeyer (1939) working 

 with seedlings of short-leaf and loblolly pine [Finns taeda Linn.) found that 



