(345) 



last for only brief periods, not long enough to warm up the soil. 

 This goes to indicate that the temperature conditions under the 

 hardwood, with their slightly warmer soil and slightly cooler air, 

 and with less spread between the maxima and minima, are a little 

 more favorable than under the hemlocks. In addition, the 

 moisture under hardwoods is more favorable on account of the 

 lower evaporation. 



The relation between the hemlock and hardwoods at Ithaca 

 with respect to the i8 inch soil temperature is the same as at 

 New York. At 6 inches the differences between the two Ithaca 

 stations are extremely small. 



At New Haven, the ridge top hemlock forest was warmer in all 

 respects than that growing on the north slope. In soil tempera- 

 ture at both depths, as with mean air temperature, the New 

 Haven stations were intermediate between New York and Ithaca. 

 It is interesting that at i8 inches all the figures, and at 6 inches 

 the maxima, show the ridge top to be closer to New York, and 

 north slope closer to Ithaca. Thus the difference in site tends to 

 bring about differences in certain environmental factors resem- 

 bling differences produced by considerable distances. This is 

 merely another example, on a much smaller scale, of the well- 

 known site differences between north slopes and south slopes 

 which occur in the mountains of the southwest. 



Considering the New York hemlock grove as roughly approxi- 

 mating the southern point in the range of the hemlock type, and 

 Cranberry Lake the northern point, the temperature figures in 

 Table I give an indication of the temperature range of the type 

 for the growing season. For convenience these figures have 

 been brought together in Table II, to which has been added the 

 number of degrees of spread in the range. 



A glance at Table II shows that the range of temperatures 

 covered by the hemlock type is not large, I2° for mean air temper- 

 ature, io° for mean soil temperature at 6 inches, and ii° for mean 

 soil temperature at i8 inches. It is possible that more widely 

 separated stations would extend this range somewhat, but 

 probably not very much. 



Fortunately we have a comparison for the northern limit. On 

 Mt. Desert Island, Maine, soil temperatures were taken at the 

 same levels in the same manner under a series of forest types. 

 The coldest of the series was a spruce type distinctly more 



