ON THE OCCURRENCE OF PINUS BANKSIANA IN 

 SOUTHEASTERN MINNESOTA 



C. O. ROSENDAHL and F. K. BUTTERS 



University of Minnesota, Minneapolis, Minnesota 



The main pine forests of Minnesota occur to the northeast of 

 a Hne drawn, roughly speaking, from near the northwestern 

 corner of the state in a southeasterly direction to the Wisconsin 

 boundary at about latitude 45°30'. This line is not straight 

 but shows a marked convexity towards the southwest, amount- 

 ing to about 75 miles in its middle portion. In the northwest 

 the pine woods come within 50 miles of the North Dakota bound- 

 ary, being there separated from the prairie country by a strip of 

 deciduous forest and brush 15 to 35 miles in width. The greatest 

 south west ward extension of the pine forest is just back of a 

 great series of lakes running in a southeasterly direction through 

 Becker, Douglas, and Otter Tail counties. In the southeast 

 the boundary runs in a nearly straight east and west direction 

 immediately south of the 46th parallel of latitude. (See map of 

 forest areas.) A few miles east of the Wisconsin border it again 

 turns to the southeast and extends in that direction to the 

 south central part of Wisconsin. The deciduous forest belt to 

 the west and south of the pine woods, which is very narrow in 

 the north, widens considerably southward and about latitude 45° 

 reaches a maximum width of over 100 miles. 



The original distribution of the three species Pinus Strobus L., 

 P. resinosa Ait., and P. Banksiana Lamb., within the evergreen 

 forest area was determined largely by soil conditions. The Jack 

 Pine (P. Banksiana Lamb.) occurred most abundantly on sandy 

 outwash plains, such as those which extend from Mille Lacs 

 westward nearly to the boundary of the pine area, and in the 

 great paleozoic sand plains of central Wisconsin. The white pine 

 {P. Strobus L.) was found particularly on the more clayey soils 



107 



THE PLANT WORLD, VOL. 21, NO. 5 

 MAY, 1918 



