Large Scalps Improve Survival 

 and Growth of Planted Conifers 

 in Central Idaho 



John P. Sloan 

 Russell A. Ryker 



INTRODUCTION 



Competition for available soil moisture between 

 associated vegetation and young trees must always be 

 considered when planning reforestation efforts in 

 Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] 

 Franco) and ponderosa pine (Pinus ponderosa Dougl. ex 

 Laws.) forests of central and southern Idaho. Elk sedge 

 (Carex geyeri F. Boott), pinegrass (Calamagrostis 

 rubescens Buckl.), and other grasses are especially com- 

 petitive with tree seedlings because the lateral extension 

 of their root systems allows them to exploit the same 

 soil zones as planted trees when located as far away as 

 2 ft (0.61 m) or more from the tree (Loewenstein and 

 others 1968). Of these grasses, elk sedge is the most 

 competitive in central Idaho (Spence and Woolley 1936). 



Elk sedge is a fibrous-rooted species that produces a 

 greater number of roots and penetrates the soil to a 

 greater depth than its grass and herb associates (Spence 

 1937). It is a perennial that tolerates unfavorable condi- 

 tions such as high moisture stress (Sampson 1917). The 

 root system of elk sedge is much more extensive than 

 the aboveground foliage (fig. 1). Although the plant 

 diagrammed in figure 1 is only 12 inches (30 cm) tall and 

 10 inches (26 cm) wide, the roots spread 56 inches 

 (142 cm) and reach a depth of 75 inches (190 cm). 

 Because of elk sedge's extensive root systems and its 

 ability to compete for soil moisture, the spaces com- 

 monly found between sedge plants are often occupied 

 below ground and may not be good spots to plant trees. 



Elk sedge is present in most inland Douglas-fir and 

 ponderosa pine forests. Of 49 central Idaho forest habi- 

 tat types that have Douglas-fir either as a climax spe- 

 cies or a major serai species, 44 have elk sedge in the 

 undergrowth (Steele and others 1981). In 10 habitat 

 types, elk sedge was found in every stand sampled. 

 Canopy coverage of elk sedge was estimated as high as 

 43 percent. Moreover, because of its extensive root sys- 

 tems, the effective site occupancy of elk sedge was much 

 greater. 



Other grasses with root systems less extensive than 

 elk sedge can also be excessively competitive where 

 coverage is high. In California, Baron (1962) planted 

 ponderosa pine seedlings for three consecutive years in 

 plots he had sown to big bluegrass (Poa ampla Merr.), 

 hard fescue (Festuca ovina duriuscula L.), pubescent 

 wheatgrass (Agropyron trichophorum K. Richter.), 

 redtop (Agrostis alba L.), orchard grass {Dactylis 

 glomerata L.), perennial ryegrass {Lolium perenne L.), 



tall oatgrass (Arrhenatherum elatius [L.] Presl.), and 

 timothy (Phleum pratense L.). Establishment of the pine 

 seedlings became less successful each year as competi- 

 tion from the grasses increased. Larson and Schubert 

 (1969) showed that for ponderosa pine, both root and top 

 growth was greater when seedlings were grown in the 

 absence of competition from Arizona fescue (Festuca 

 arizonica Vasey) and mountain muhly (Muhlenbergia 

 montana [Nutt.] Hitchc). 



30 

 20 

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 10 

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C 



* 100 



110 

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»• . "V!. \. •%»*■•-• , ■ . • < -\ • /.,. 



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Figure 1.— Representative diagram of a 

 fibrous root system of sedge (Carex sp.) from 

 a north slope in the Boise River watershed, 

 southwestern Idaho (Spence and Woolley 

 1936). 



1 



