630 FUNDAMENTALS OF FRUIT PRODUCTION 



Attention may be called to some of the northern finger-like extensions 

 of the Lower Austral zone into latitudes that for the most part belong in 

 the Transition zone. Those along the eastern shore of Lakes Michigan 

 and Huron, the southern shores of Lakes Erie and Ontario and the eastern 

 shore of Lake Champlain are cases in point and illustrate the extent to 

 which chmate is tempered and consequently life zones are modified 

 through the influence of large bodies of water. Lippincott gives one 

 concrete illustration of this influence :*i On Jan. 1, 1864, a cold wave 

 swept over the north central part of the United States. Many Minnesota 

 points registered temperatures as low as — 38°F. ; at Milwaukee the 

 thermometer went to — 30°F.; yet at Holland, Mich., across Lake Michi- 

 gan from Milwaukee —8°F. was the lowest temperature recorded. 

 Further inland, at Lansing, Mich., however, — 22°F. was experienced. 

 Peach buds were uninjured in a narrow belt along the eastern shore of the 

 lake but were killed at distant points. The data for Milwaukee and 

 Grand Haven in Table 5 show that this influence is constant. 



Influence of Altitude on Air and Soil Temperatures. — It is well known 

 that an increase in altitude is accompanied by many of the same changes 

 as an increase in latitude, the most important being one in temperature. 

 It is true also that an increase in altitude is accompanied by certain 

 changes in physical environment that are not found at correspondingly 

 higher latitudes. Thus Kerner and Oliver report that in the Tyrolese 

 Alps at an altitude of 2600 meters the chemical activity of the sun's rays 

 is 11 per cent, greater than at sea level. This alone may account for 

 some of the peculiarities of plant associations noted at different altitudes 

 and possibly may go far toward explaining the more brilliant and intense 

 coloring of certain fruits and their better finish at high altitudes. The 

 same authors report a different ratio between mean soil and air tempera- 

 tures at high as compared with low elevations (see Table 7) and this too 

 may either intensify or suppress, as the case may be, the differences 

 associated with variations in air temperature only. 



Table 7. — Increase of Mean Soil Temperature Over Mean Air Temperature 

 WITH Increased Altitude in Tyrolese Alps^^ 



