Deer browsing was more common on pine seedlings growing at Bluesky than on those 

 at Warland and Jackson. Douglas-fir seedlings were occasionally browsed. In the 

 studies at Dunn and Butler deer damage on pine seedlings was 14 and 1 percent, res- 

 pectively. Most of this damage occurred in the winter of 1953 and 1954. 



DISCUSSION 



Natural regeneration of ponderosa pine is spasmodic throughout its range except 

 in the Black Hills (USDA Forest Service 1965). Successful establishment usually is 

 dependent on: (1) adequate viable seed; (2) receptive seedbed; and (3) favorable 

 climatic conditions during the first year. Of these three, the forest manager is able 

 to manipulate the seed source and seedbed most easily. At present, little can be done 

 to predict or influence climatic conditions, but through judicious control of seed 

 source and seedbed the micro-environment around young seedlings can be enhanced during 

 most years. 



These studies quantify the effect of some physical and biological factors that 

 limit seedling establishment in western Montana. Chief among these limiting factors 

 are: (1) heavy losses of the potential seed crop during the 2-year cone development 

 period; (2) heavy seed loss following dispersal; and (3) high seedling mortality. 

 The odds are close to one or two in a thousand that a potential pine seed in the ovu- 

 late bud stage will become a surviving seedling. The additive effect of the above 

 losses point to why it is difficult to successfully regenerate stands of ponderosa 

 pine under normal conditions in most years (table 7) . 



The probabilities of establishing ponderosa pine seedlings are greatest when good 

 seedbed preparation is coordinated with maximum seed production. Consequently, forest 

 managers need to know as early as possible when a good crop of seeds can be expected. 

 Factors that affect the initiation of ovulate buds as well as their subsequent devel- 

 opment are not well understood. However, above average temperatures during the period 

 of flower bud initiation (24 to 28 months before cone maturity) have been found to be 

 closely correlated with good flower bud initiation and subsequent cone crops 

 (Daubenmire 1960, Maguire 1956). Although it is unlikely that foresters will ever be 

 able to predict cone crops with great accuracy, examination of the ovulate buds or 

 first-year conelets can provide an estimate of the developing cone crop as much as 2 

 years before seed dispersal. 



These studies have identified factors that drastically reduce the potential cone 

 crop. Most of the first year cone losses resulted from abortions, but squirrels caused 

 a majority of the second year losses. At present we do not understand the reason for 

 the consistently high abortion rates and consequently can do nothing to reduce them. 



Squirrels not only reduce current cone crops but future crops as well (Squillace 

 1953, Adams 1955). Squirrels usually sever the cone-bearing shoots just below the 

 mature cones. This also eliminates any 1-year-old conelets or ovulate buds developing 

 on the shoot beyond the cut. Also, such cutting may reduce the flowering potential 

 for a few seasons. Squirrels also frequently cut shoots from the ends of branches 

 in the winter to feed on the cambium layer, thus reducing still further the potential 

 for cone production (Adams 1955). As a corrective measure, it may be necessary at 

 times to place metal bands on seed trees in partially cut stands or in seed orchards to 

 prevent squirrels from climbing (Tackle 1957, 1959). 



14 



