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F-igvre 10. — Average length 

 of lateral roots per seed- 

 Ivng, with statistical 

 comparison of treatments. 



TREATMENT 



Seedling biomass . --The ovendry weights for shoots and roots of seedlings from in- 

 dividual treatments are shovm in figure 11. The treatments are ranked according to 

 total seedling weights. The lines of significance above the x-axis point out shoot 

 comparisons, and the lines below show root comparisons. Total weight comparisons are 

 similar to those for root weights. 



The fire plots, again, had the heaviest seedlings, including both shoots and roots. 

 The seedlings from the opening-litter and opening-cleared treatments were similar in 

 total weight, with the former having heavier shoots and the latter producing heavier 

 roots. The seedlings from the litter plots were next, having slightly heavier shoots 

 and roots than those from the opening-natural plots. The natural plots produced seed- 

 lings with the least biomass, including the smallest shoots and the smallest root 

 systems . 



Mycorrhizae . --Figure 12 shows average mycorrhizal infection for the 15 seedlings 

 from each treatment. There were no seedlings that were completely devoid of mycor- 

 rhizae. The fire plots as a group had seedlings with the least infection because of 

 increased soil pH, increased soil nutrient status, and the physical action of heat on 

 the fungi [Hacskaylo and Snow 1959; Wright 1957) . Mycorrhizal associations do not nor- 

 mally occur in great numbers and may be entirely absent when nutrients, especially nitro- 

 gen, become less limiting (Powells and Krauss 1959). The natural plot seedlings had 

 the next lowest mycorrhizal numbers, slightly below the opening- litter seedlings. Sub- 

 stantial light is apparently a prerequisite for mycorrhizal formation because reserve 

 carbohydrates from high rates of photosynthesis are necessary for fungal associations 

 (Hacskaylo and Snow 1959). Therefore, the high degree of shading coupled with apparent 

 low soil temperatures caused by the deep litter layer on these natural plots could have 

 been an important factor in causing low numbers of mycorrhizae. The greatest number 

 of tips were observed on the litter treatment seedlings. 



19 



