Once a seed has germinated and the seedling begins its struggle for survival, fac- 

 tors other than competition can be destructive. Because pine sites generally have high 

 summer temperatures and low precipitation, the young trees, though drought resistant, 

 can succumb to lack of moisture (Wellner 1970) and to insolation (Foiles and Curtis 

 1965). Frost heaving can uproot and kill young trees during their first winter. Live- 

 stock, big game, and porcupines feed on and often kill sapling pines (Black 1970) and 

 trees of nearly all ages can be damaged by disease (Roth 1970) . In addition, deep shade 

 can adversely affect or even kill young trees (Pearson 1936) . 



Weaver (1943, 1951) states that fire played an important role in structuring the 

 pine forests and permitted a continuation of their success on sites that are now stag- 

 nating or experiencing a species change due to fire exclusion. Cooper (1960) has also 

 shown the values of periodic burning in ponderosa forests. Fire-treated sites had larger 

 trees, healthier regeneration, and a more open structure thereby providing less intra- 

 specific competition than unbumed sites. Biswell (1973) stated, "Ponderosa pine-grass- 

 lands are dependent on frequent surface fires for their health and stability and on the 

 other hand, frequent surface fires are dependent on the plant communities that produce 

 the fuels that carry fire, each being dependent on the other." 



Because natural fire has often been shown to be beneficial, many feel that prescribed 

 fire can likewise be an effective tool in ponderosa pine regeneration. Roe and Squillace 

 (1950) have illustrated that prescribed fire markedly increased pine reproduction. In 

 northwestern Montana, broadcast burning was followed by the establishment of twice as 

 many seedlings as on unburned areas (Shearer and Schmidt 1970). Schultz and Biswell 

 (1959) studied the effects of different seedbed preparations on ponderosa pine seedling 

 emergence. They found that the sooner the seedfall occurred after burning, the more 

 seedlings appeared. This was attributed to the deterioration of seedbed conditions 

 through time, caused by the gradual buildup of competition, crusting and smoothing of 

 the soil surface by rain and wind, and the accumulation of fallen needles. 



Additional effects of fire upon ponderosa pine regeneration were demonstrated in 

 a number of studies by Vlamis and associates. In the first study they showed that fire 

 increased the amount of nitrogen and phosphates in the soil (Vlamis and others 1955) . 

 Later, their experiments revealed that ponderosa pine seedlings responded greatly, by 

 increased growth, to artificially added nitrogen (Vlamis and others 1957), and to burned 

 soils, presumably because of increased nutrients (Vlamis and others 1956). 



STUDY AREA 



The study site is 40 miles (64 km) northeast of Missoula and includes about 14 acres 

 (5.6 ha) of level ground on the Blackfoot-Clearwater Game Range. The site is dominated 

 by a ponderosa pine overstory with intermittent openings in the stand where pine regen- 

 eration is frequently abundant. Openings are of various shapes, and range in size from 

 a few acres to small spaces between canopies. Pine regeneration is nearly absent in 

 the understory. 



The entire stand is located on valley-bottom alluvial soils (Clapp 1932), bound by 

 large grass fields on the east and west and foothills on the north and south. The site 

 is very good for ponderosa pine growth, with an index of 95 feet (29 m) in 100 years 

 (Meyer 1938). However, close observation indicates that Douglas-fir is invading the 

 understory and will probably become dominant. This site is therefore a Douglas-f ir-- 

 pine grass habitat type [Pseudotsuga menziesii/Calamagrostis rubesoens, Agropyron 

 spicatwn phase) (Pfister and others 1977) . 



2 



