35 

 the total number of fungi (r = 0.89 to 0.94) than with any single species 



(r £ 0.85). The presence of a specific organism was not as influential 

 on the activity of the pathogen as was the total, composite fungal 

 community. The higher correlations obtained when the activity of the 

 pathogen was compared to total number of detected fungi agrees with 

 Park's (25) conclusion that the probability of an organism coming in 

 contact with a single species is much less likely than the organism 

 interacting with the entire community. The lack of specific antagonism 

 of any one species towards the pathogen was further supported when 

 several isolates of the major recolonizing species did not show antago- 

 nism towards the pathogen on nutrient agar (unpublished results). The 

 changes in species composition and dominance in nonamended soils were 

 attributed to different successional stages of recolonization. Fungal 

 succession in treated soil has been the subject of several reviews (4,17, 

 42) . The mechanism of succession usually is similar to that proposed by 

 Garrett (9) for microbial succession on plant debris, in which the avail- 

 able carbon source determines which organisms are dominant. In opposi- 

 tion to reports of fungal succession are instances in which single spe- 

 cies remain dominant during the entire exploitation of the substrate 

 (5 » 10 ,18 ,40 ) . This occurs when a species is introduced artificially at 

 high inoculum densities to a substrate prior to colonization by other 

 organisms. Bruehl and Lai (5) reported that the advantage of prior colo- 

 nization of wheat straw increased the competitive saprophytic ability of 

 several fungi. The importance of prior colonization in soil systems is 

 evident in these studies by the decreased immigration rates by naturally 

 occurring fungal species in amended soils. In addition, when the patho- 

 gen was added to freshly fumigated soil, it was able to proliferate 



