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Table 3 Mean ring width before and after HWA arrival at each of the six study sites

From: Radial growth changes following hemlock woolly adelgid infestation of eastern hemlock

Site

Years of HWA infestation

Sample size (number of annual rings)

Mean ring width before HWA (mm)

Mean ring width after HWA (mm)

t value

p value

Georgia

4

320

2.83 (1.23)

2.71 (1.32)

−0.72

0.413

North Carolina

5

360

2.20 (1.52)

1.23 (1.38)

−7.24

<0.001*

Virginia

13

858

2.58 (1.50)

1.72 (1.28)

−6.17

<0.001*

West Virginia

18

1,396

1.02 (0.51)

1.01 (0.52)

−0.51

0.612

Pennsylvania

17

1,428

1.42 (0.80)

1.01 (0.70)

−6.45

<0.001*

Massachusetts

15

1,230

1.65 (0.76)

1.87 (1.21)

2.08

0.044*

  1. An asterisk marks the significant changes in ring width across the two time periods (α = 0.05). The sample size relates the total number of rings included in the t test—half of these rings were from before HWA arrival and half were from after HWA arrival. The values in parenthesis after the mean ring widths are standard deviations
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Annals of Forest Science

ISSN: 1297-966X