Kelley — 86 — Mycotrophy 



Prairie: — The other habitat to be considered is prairie. Strictly 

 speaking, prairie is a special sort of meadow once found in the central 

 United States but the term is now loosely applied to non-forested 

 lands throughout the more northern portion of the Mississippi Valley. 

 Virgin prairie is now virtually extinct throughout the area and the 

 soils have been changed by agricultural practice. Since trees were 

 absent in the prairie area, except along water-courses and on some 

 rougher lands at time of discovery by white men, it has been supposed 

 the mycorrhizal fungi were absent from the prairies. Yet it appears 

 obvious that prairie grasslands existed simply because tree growth 

 was excluded by fire and difficulties of ecesis, and recent studies in 

 Iowa indicate a rapid spread of oak-scrub over former prairie lands 

 to the annoyance of the farmer. "Harrison County (Iowa) vegetation 

 was used by Shimek ... to support his thesis of climax prairie in 

 Iowa, yet 30 years later Quercus macrocarpa is spreading so rapidly 

 on the less intensively farmed lands of the country as to constitute a 

 serious economic problem". (McComb & Loomis, 1944). Apparently 

 these trees have no difficulty in ecesis. The author, while living on the 

 Iowa prairies, has personally seen how readily bur-oak becomes estab- 

 lished wherever prairie sod is uprooted. 



But Hatch (1936) stressed a reputed absence of mycorrhizal 

 fungi from prairie soils, meaning by "prairie" apparently what is 

 otherwise known as "dry prairie" or "steppe". He noted from the 

 literature that "16 nursery and plantation failures have occurred in 

 widely separated regions of the world" due to "lack of a biologic 

 factor in the soils". He secured, through friends, some "prairie soil" 

 from Wyoming for his experiments. 



As a matter of fact, Wyoming is several hundred miles west of 

 the prairies ; it is five thousand feet higher in altitude ; and it has a 

 different climate. The name, Prairie, may not be applied indiscrimi- 

 nately to all grasslands. The plains of North America, the pampas of 

 South America, the steppes of Asia, and the veld of South Africa 

 are all grasslands ; but they are none of them prairies. 



In this Wyoming soil Hatch grew seedlings of Piniis Strohus and 

 found growth poor and unthrifty when mycorrhizae were absent but 

 on inoculation with pure culture fungi of several species growth 

 became good. N, P, and K determinations of the seedlings were made 

 after 10 months growth, showing marked increase in the absorption 

 of N, K, and especially P by the mycorrhizal plants. Hatch believed 

 the evidence was conclusive in showing that the pine seedlings grown 

 in this soil did not obtain sufficient nutrients to support normal growth 

 when mycorrhizal fungi were absent ; and he repeated his conclusion 

 in a paper published the following year. Rayner (1937), ignoring 



