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Control Snow Removal

96-US

97-US 96-MS 97-MS

Year - Site

Figure 5.6. Average seed weight 1996 and 1997, 2920 and 3170 m sites. US, upper site; MS, middle site. Error bars represent 95% comparison limits between control and treatments in the same year-site combination.

Table 5.7. Three-way ANOVA. Effect of Snow Removal on Average Seed Weight, Upper and Middle site 1996, 1997 (2599 seeds from 249 individuals).

Variance

Table 5.7. Three-way ANOVA. Effect of Snow Removal on Average Seed Weight, Upper and Middle site 1996, 1997 (2599 seeds from 249 individuals).

Variance

Source

Effect

LSdf

Ddf

Component

F

P

Treatment

Fixed

1

15.8

1.85

0.1929

Site

Fixed

1

15.8

0.0

0.9446

Year

Fixed

1

229

51.58

0.0001

Block (Site)

Random

4

0.0

Treatment x Site

Fixed

1

15.8

1.54

0.2325

Treatment x Year

Fixed

1

229

5.19

0.0236

Site x Year

Fixed

1

229

1.75

0.1870

Treatment x Site x Year

Fixed

1

229

1.16

0.2835

Treatment x Block (Site)

Random

4

0.00634

Year x Block (Site)

Random

4

0.0

Treatment x Year x Block (Site)

Random

4

0.0

Error

Random

225

0.03853

Treatment, site, and year were treated as a fixed effect and block within site as a random effect. LSdf = least squares degrees freedom, Ddf = denominator degree of freedom. Significant effects are shown in boldface type. Variance component values are reported for random effect and F ratio and probabilities are reported for fixed effect.

Treatment, site, and year were treated as a fixed effect and block within site as a random effect. LSdf = least squares degrees freedom, Ddf = denominator degree of freedom. Significant effects are shown in boldface type. Variance component values are reported for random effect and F ratio and probabilities are reported for fixed effect.

altitudes, seed weight did not respond significantly to treatment (p > 0.05). In 1997, seed weight responded significantly to the snow removal treatment only in the upper site (p = 0.0505); in the upper site, seeds from the snow removal treatment weighed significantly more than those in the control plots, while no significant difference was found in the middle site that year (Fig. 5.6). It is possible that an increase in the growing season's length is more important at higher elevations. Galen and Stanton (1991, 1993) working at 3,550 m elevation in a similar environment, found a significant effect of snowpack-duration on seed weight for another member of the Ranunculaceae family. As with seed number, it will be useful to conduct regression analyses comparing the effect of snowmelt date on seed weight across sites.

Seedling Size in a Common Garden (1996 cohort) After 1 year there was a significant difference in growth (cotyledon area estimate) between controls and treatments for the seeds coming from the upper site (p = 0.033) (Table 5.8). The seedlings from the snow removal treatment had larger leaves (cotyledons). The mean leaf area for the controls was 20.32 mm2 (SE = 0.78, n = 370) compared to 22.14 mm2 (SE = 0.77, n = 394) for seedlings from the snow removal treatment. Most of the variance in growth came from individual seed variation (86%).

Table 5.8. One-way ANOVA. Effect of Snow Removal on Leaf Area Estimate.

Source

Effect

LSdf

Ddf

Variance Component

F

P

Treatment

Fixed

1

8.06

6.6

0.033

BlockSe

Random

9

3.5036

Treatment x BlockSe

Random

9

0.0

BlockMa

Random

4

0.0

Treatment x BlockMa

Random

4

0.9101

Treatment x BlockSe x BlockMa

Random

36

Error

Random

699

26.1127

Seeds were collected in snow removal experiment, 1996, upper site and grown in common gardens at 2920 m (n = 763). LSdf = least squares degrees freedom, Ddf = denominator degree of freedom. BlockSe = block of seeds, BlockMa = block maternal plants. Significant effects are shown in boldface type. Variance component values are reported for random effect and F ratio and probabilities are reported for fixed effect.

Seeds were collected in snow removal experiment, 1996, upper site and grown in common gardens at 2920 m (n = 763). LSdf = least squares degrees freedom, Ddf = denominator degree of freedom. BlockSe = block of seeds, BlockMa = block maternal plants. Significant effects are shown in boldface type. Variance component values are reported for random effect and F ratio and probabilities are reported for fixed effect.

In summary, only some of the measures of fitness measured seem to respond to snow removal experiments. Flower number was not affected in the expected way (Table 5.4). Seed number per fruit was significantly less in the snow removal treatments than in the controls only in the middle site for the year 1997 (Fig. 5.5). Seed weight response seems to be year-specific (Table 5.7), seeds from the treatment weighed significantly more than the controls only in the upper site, 1997. Finally, the leaf area of seedlings (1996-cohort) from the upper site was significantly larger for the treatments than for the controls.

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