Table 1--Average number of sound and total seed per acre, with standard errors, falling on plots during the period 1974-1978 by species and density level

8,162+ 1,795 71.5 385+ 385 5,509+1,542 302,759+15,138 23.4 1,195+ 823 26,836+5,367

7.0 13,367+2,807 20,658+3,511 64.7 3,240+1,184 5,265+1,454 61.5 4.5 18,632+3,913 96,809+8,713 19.2 17,417+3,603 45,365+8,259 38.4

79,270+ 7,134 362,872+16,329 21.8 1,540+ 976 30,400+5,472 7,696+ 1,847 51,564+ 5,672 14.9

-

5.1 1,539+ 875 0

7,697+1,847 1,540+ 862

65,033+6,742 11.8 10,176+2,256 33,563+4,862 30.3 10,006+2,853 15.4 3,977+1,609 12,528+2,587 31.7

3,463+ 1,281

Total

6,542+ 1,766 52.9 6,927+1,662 11.1 8,081+2,020 90,429 8,138 420,978+18,944 21.5 2,310+ 785 38,866+4,275 5.9 17,318+3,403

770+ 623

130 ft 2

211,785+10,589 5,550+ 1,554

3,139+ 1,161

Total

7,028+ 1,968 44.7 1,924+1,058 11,281+2,482 17.1 11,833+2,840 21,934+3,412 53.9 865+596 1,250+818 69.2 220,474+11,023 774,595+30,983 28.5 3,078+1,170 36,578+4,755 8.4 15,054+3,312 123,523+9,882 12.2 20,297+3,529 47,523+5,398 42.7 1/No seeds were found in any traps from the 1973 seed year.

The typical pattern of seedling invasion and mortality is illustrated in figure 3. About 30 to 40 percent of the large numbers of seedlings present in 1975 had died by 1978 with most of the mortality occuring during 1976 and 1977. Mortality rates of grand fir and red fir were similar. New seedlings were found on the plots each year from the light cone crops of 1975 through 1977 but not in sufficient numbers to offset the losses of seedlings originating in 1975. It is apparent from these results that a year of heavy cone production soon after the seed cut offers the best chance of quickly obtaining adequate natural regeneration. Although the bulk of natural regeneration generally becomes established in "waves" following heavy seed years, it is possible to obtain satisfactory stocking from light cone crops over a number of years as long as the seed bed remains receptive. Williamson (1973) also reported that adequate natural regeneration of Douglas-fir in the Cascades of western Oregon was obtained from seedling establishment during years of low seedfall.

These observations suggest that it is not necessary to schedule seed cuts to coincide with heavy seed years.

In the fall of 1978, 5 years. after the study was begun, all subplots were well stocked with seedlings ranging from an average of 1,220 per acre on 90 ft2-none treatment to 7,240 per acre on the 130 ft2-bulldoze treatment

(fig. 4). Regardless of slash treatment, the high density overstory always resulted in the most regeneration. Similarly, the bulldozed subplots always contained the most seedlings regardless of overstory density level. The proportion of pine in the regeneration increased from about 3 percent in 1975 to about 11 percent in 1978 primarily because of considerable numbers of new ponderosa pine seedlings found in the fall of 1978.

Regional standards for defining satisfactory stocking of true fir regeneration have not yet been established. At this time, an estimate of adequate stocking can be obtained by using the stocking level curves for Douglas-fir which suggest 400 to 500 trees per acre as sufficient.5/ With this standard, all subplots in this study were adequately stocked after 5 years.

The sound seed-to-seedling ratio gives an indication of the environmental conditions that affect germination and early seedling survival, lower ratios indicating more favorable conditions. The superiority of the bulldozing slash treatment for obtaining natural regeneraton is shown in these ratios for the 1974 seed year

5/Forest Service, Region 6, Silvicultural Examination and Prescription Handbook, 2409.26d.

(table 2). For both grand fir and red fir, the sound seed-to-seedling ratio was always the lowest for the bulldozed treatment at all density levels. Also, in all subplots, red fir was more efficient than grand fir in producing seedlings from seed having ratios some 3 to 8 times lower than grand fir. In the bulldozed subplots at the high density level, the red fir seed-toseedling ratio was only 2:1--that is, for every two sound seeds falling in 1974, one seedling was counted in the fall of 1975.

Height growth of the fir seedlings was slow--the tallest seedlings averaging about 10 to 11 cm after 5 years (table 3). Both grand fir and red fir seedlings. grew at about the same rate, and no significant differences in height existed among density levels or slash treatments. Although growth during this initial 5-year period,

on the average, has been slow, many of the more vigorous seedlings showed good growth during 1978, and the rate of height growth should increase in the future (fig. 5).

Seed Bed Conditions and

Regeneration

Because of the removal of nearly all organic matter on the bulldozed subplots, the percentage of milacres classified as mineral soil in 1974 was high (table 4). Litter fall during the following 5 years decreased the area of bare mineral soil and increased the number of milacres in the light litter and slash category on these subplots (fig. 6). Only minor changes in seed bed conditions occurred in the none, crush, and lop and scatter treatments since these subplots had considerable amounts of litter and slash present in 1974.