Introduction 



The Idaho Batholith (fig- 1) has some prominent characteristics which are serious 

 obstacles to forest management and regeneration. The shallow, granitic soils are nota- 

 bly coarse grained and provide severely limited moisture storage and a high evaporative 

 potential.-^ ^ On steep slopes these soils have a high inherent erosion potential 

 (Megahan and Kidd) . ^ High intensity rains (Kidd 1961; 1964) from frequent and unpre- 

 dictable summer convectional storms further aggravate erosion potentials. These storms 

 also provide some relief from soil moisture deficits. Established vegetation makes 

 almost full use of available soil moisture but stabilizes soil in the process. 



The land manager faces a dilemma. If trees are to be harvested, he must find ways 

 to maintain a vegetative cover to control erosion yet reduce vegetative competition so 

 that replacement seedlings have enough soil moisture to survive and grow. Furthermore, 

 his harvesting methods will be severely limited by the steep slopes. 



A series of ponderosa pine {Finns ponderosa Laws) planting tests in the Idaho 

 Batholith (1961 to 1964) were primarily concerned with controlling vegetative competi- 

 tion at the time the seedlings were planted and for several years thereafter.^ 



We evaluated hand scalping, a pre-emergence herbicide (simazine) , ^ spot burning, and 

 periodic weeding techniques, mulches of straw, plastic film, and glass fiber (table 1). 

 Slope aspects and soil depths were other variables considered. Highly variable climatic 

 factors occurring from year to year were a confounding influence. 



Four tests were installed on the Zena Creek logging study area, Payette National 

 Forest, and one test at the Boise Basin Experimental Forest on the Boise National Forest 

 (fig. 1). 



Tests were installed in habitat types (h.ts.) that closely resemble, and probably 

 are, the Daub enmi res ' (1968) Pseudotsuga menziesii - Physocarpus malvaaeus (Jhe 

 Douglas-fir--Ninebark h.t.). Our results specifically apply to this presumed h.t. and 

 should only be extended to other h.ts. with reservations. The serai nature of ponder- 

 osa pine occurrence in this h.t. is important in any consideration of regeneration. 



•^Richard Alvis, John Arnold, and others. Soils of the Zena Creek Logging Study, 

 Payette National Forest. 1960. (Unpublished report on file (2510) at USDA Forest Serv., 

 Region 4, Ogden , Utah.) 



^0. C. Olson. A soil survey report of the Boise Basin Experimental Forest. 1965. 

 (Unpublished report on file (2510) at USDA Forest Serv., Region 4, Ogden, Utah.) 



^Walter F. Megahan and W. J. Kidd, Jr. Effects of logging and logging roads on 

 erosion and sediment deposition from steep terrain. In preparation. USDA Forest Serv., 

 Intermountain Forest and Range Exp. Sta., Ogden, Utah. 



"^Dale 0. Hall. Conifer planting techniques, survival and height growth in the 

 central Idaho batholith. 1969. (Unpublished final report for Study FS- INT-1202-494 on 

 file at USDA Forest Serv., Intermountain Forest § Range Exp. Sta., Ogden, Utah.) 



^Simazine is the common name for 2-chloro-4, 6-bisethylamino-l , 3, 5-triazine . 



1 



