282 



F. L. Bunnell et al. 



T looa 



— o 

 o -^ 

 o* a> 

 c o 

 3 >. 

 l^ E 



500- 





^12 cm depth 

 De 7 cm depth 



1 



I 



a 





ill 



O-m .1.19 .2.29 .3.39 4.49 .5.59 .6.69 .7.79 .8.89 



in 

 o 



l\ 



m <^ 



o E 

 o> 



C CP 



3 



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I 



an. 



IDJ 



0.09 .1.19 .2.29 .3.39 .4.49 .5.59 .6.69 .7.79 



Bulk Density, g cm' 



.8-89 



FIGURE 8-10. The density and biomass of soil fungi 

 arranged by soil bulk density and soil depth. (After 

 Laursen 1975.) 



associated with differences in fungal biomass per volume of soil. Total 

 carbon in the top 15 cm of polygon troughs (Figure 7-1) is about half that 

 found in the wet meadows and the basins and rims of low-centered poly- 

 gons; fungal biomass in soils of troughs is also lower than in basins, mea- 

 dows or rims (Figure 8-4). However, fungal biomass per volume of soil 

 shows no consistent relationship with bulk density alone (Figure 8-10). 

 Apparently at the highest bulk densities some factor, such as poor aera- 

 tion, reduces the "hospitality" of a volume of substrate regardless of the 

 amount of organic substrate available. 



Inorganic Nutrients 



Observed relationships between soil fungi and amounts of phos- 

 phorus are equivocal but suggest that phosphorus is limiting to fungal 

 growth in some microtopographic units. No clear relationship appeared 

 in the surface soil between daily measurements of resin-extractable 

 phosphorus expressed on a volume basis and fungal density (values of 

 the correlation coefficient ranged from 0. 10 in polygon troughs to 0.42 in 

 basins of low-centered polygons). However, fungal density and biomass 



