1981). The number and location of safe sites control the 

 size and the distribution of pinyon seedling populations. 



Estimates showed that both parallel and tree-to-tree 

 transects had greater seedling density in the duff sur- 

 face microsite (table 1). Differences in seedling density 

 estimates between transect types occurred and may be 

 the result of sampling only larger trees in tree-to-tree 

 transects. Nevertheless, the duff microsite appears more 

 favorable for seedling establishment, a response opposite 

 that observed for most understory species (Everett and 

 Koniak 1982). Understory provided little or no cover 

 (X = 2.6 percent ground cover; CV = 130 percent) on 

 microsites containing seedlings. 



Table 1. — Proportion of total pinyon seedlings (percent) and 

 seedling density (m^) In the soil microsites and the 

 proportion of sample area occupied by each soil 

 microsite for all sites 



Soil microsite 





Duff 



Transition 



Interspace 



Parallel transects 









Percent of total 









Microsite 



46.931 



24.3'' 



28.8'' 



Seedlings 



83.03 



4.1*^ 



12.9" 



Seedling density 



.95^ 



.19^ 



.31" 



Tree-to-tree transects 









Percent of total 









Microsite 



50.23 



23.3" 



26.0" 



Seedlings 



67.03 



17.0'' 



17.0" 



Seedling density 



.72 



.41 



.34 



''Significant differences (P = 0.05) in rows denoted by superscripts. 



Total number of seedlings (78) encountered in tree-to- 

 tree transects is marginal for reliable estimates of 

 pinyon seedling distribution from the tree bole, but seed- 

 ling density definitely decreases with distance from the 

 tree bole and especially at the duff edge (table 1 and 

 fig. 1). The 150- to 200-cm distance class encompasses 

 the average duff radii (167 cm) of the sample trees. Duff 

 is shallow at the crown edge, increasing in depth under 

 the crown, and often decreasing in depth immediately 

 adjacent the tree bole. In duff, the germinating seed can 

 establish root-mineral soil contact in a microenvironment 

 less prone to desiccate the root tip as it emerges 

 from the seed hull (our own observations; Lanner 1981). 



Pinyon seedlings appear of limited importance for spe- 

 cies perpetuation in fully stocked stands. On fire-safe 

 sites, large trees rarely die and they monopolize site 

 resources over a long Ufe span, 350 years (Meeuwig 

 1979; Meeuwig and Cooper 1981). Most seedlings have 

 only a short time in which to succeed or perish because 

 of annual summer drought and sporadic drought years. 

 When stands burn, fires consume both duff and seed- 

 lings. No pinyon seedlings were recorded on prescribed 

 burns of pinyon-juniper woodlands for 5 years following 

 fire (Everett and Ward 1984). SeedUngs may represent 

 the germinating surplus seed of an efficient dispersing 

 system. The large, nutritious seeds of pinyon encourage 

 their harvest and dispersal by both rodents and birds 

 (Emmerson 1932; Vander Wall and Balda 1977; Ligon 

 1978; Lanner and Vander Wall 1980; Lanner 1981). 



The concentration of pinyon seedlings under the crown 

 provides management with an opportunity to enhance or 

 discourage natural pinyon regeneration. If regeneration 

 is to be curtailed, prescribed burning of stands or 

 individual trees automatically eliminates a majority of 

 the standing seedling crop. Exposing seedlings to the 

 full sunlight reduces seedling survival significantly. 

 Seedling survival on 10 tree harvest sites declined from 

 a preharvest total of 100 to seven and then one in the 

 first and third years following tree harvest. On four 

 adjacent uncut sites, seedlings increased from eight to 

 20 the first and third years following tree harvest. After 

 tree harvest, a moderate slash cover may be applied to 

 increase seedling survival (Meeuwig and Bassett 1983). 



O 20i- 



Q 



lU 

 lU 

 « 



O 



oc 



UJ 

 CQ 



S 

 3 



16 



12 - 



100 200 300 400 



DISTANCE TO NEAREST TREE, CM 



Figure 1.— Distribution of pinyon seedlings 

 in distance classes from the nearest tree. 

 (The 150- to 200-cm distance class encom- 

 passes the mean duff radii [X = 167 cm]). 



2 



