In layer III, variation among total root weights or weights of any of the size 

 classes is still associated with the proximity of perennial plants. Average weights 

 were computed by layer for all sampling units within 30 cm. of the edge of a living or 

 dead shrub crown or grass base (n = 48) and for those farther away (n = 42) . For layer 

 III, total weight of roots nearer the plants was 172 g./m.^; roots farther away averaged 

 129 g./m.2. The difference due to position of sample is highly significant (analysis 

 of variance) . However, this difference is considerably less in layer III than at 

 shallower depths. In the surface layer, where variances, as well as means, are sig- 

 nificantly different, roots nearer the plants weighed 275 g./m.^; roots farther away 

 weighed only 38 g./m.^. 



The underground litter is mostly near the surface, where its weight exceeds that 

 of roots (table 2) . Its horizontal distribution at that level is related to plant 

 location (fig. 1). In layer III, litter makes up less than an eighth of the mass of 

 organic material and its dispersion does not depend on proximity to plants on the 

 surface. 



Most of our so-called underground litter originated above the ground. Such litter 

 was matter barely worked into the soil surface by animal activity, especially under 

 shrub crowns, or was fine parts of surface litter overlooked in our harvest of above- 

 ground material. Over 85 percent (our cursory estimate) of the recognizable part of 

 the underground litter in layer I was comprised of leaves, empty shells of fruits and 

 seeds, small spines, and parts of twigs. Some matter of obvious root origin, such 

 as cortical slough, was sorted out as litter, but bare stelar fragments of fine roots 

 were included as root material. A few macroscopic remains of insect parts were seen: 

 body segments, appendages, and empty pupa cases. These amounted to but a slight 

 fraction of the identifiable litter. Fecal material of three kinds constituted the 

 remainder: rabbit and small rodent droppings; smaller pellets (more polygonal than 

 circular in cross section, some light-colored, some dark), presumed to be from insect 

 larvae; and finely pulverized loose particles of fibrous woody frass. The last kind 

 was the most important element of litter in layers II and III, although leaves and 

 fruit husks were found at both levels. Upon reexamination, a few unusually high values 

 for underground litter in the data for the two lower levels were found to be due to 

 concentration of small rodent feces, although no existing burrows were intercepted in 

 the sample. 



The harvest of aboveground matter (living, standing dead, and litter) weighed 

 240 g./m.^ of ground surface. Such matter was composed of the following in the propor- 

 tions listed: Atri-plex^ 63 percent; Eurotia, 11 percent; other shrubs, 1 percent; 

 perennial grass, 2 percent; other herbaceous material, 6 percent; miscellaneous unsorted 

 litter, 17 percent. The last named was com.prised mostly of leaves, fruits, and fine 

 woody material; a few rabbit pellets were also found in it. On the area harvested, 

 there were 2.4 living and 1.3 standing dead shrubs per square meter, and 0.7 living and 

 0.5 dead perennial herbs. 



9 



