Table 2 Statistics of warming and herbivory effects on NEE800, GPP800, and Re in 2017–2018.

From: Insect herbivory dampens Subarctic birch forest C sink response to warming

 

NEE800 F

NEE800 P

GPP800 F

GPP800 P

Re F

Re P

2017

 Soil OM content

0.2

0.687

6.8

0.026

41.0

<0.001

 Vascular plant cover

9.3

0.014

29.2

<0.001

42.6

<0.001

 Lichen cover

20.5

0.001

8.4

0.015

27.4

0.001

 Moss cover

1.8

0.211

0.1

0.712

7.6

0.024

 Date (D)

46.5

<0.001

121

<0.001

136

<0.001

 Warming (W)

2.0

0.190

4.6

0.062

3.1

0.119

 Herbivory reduction (H)

5.7

0.043

13.2

0.006

11.6

0.010

 W × H

1.0

0.352

3.5

0.094

7.0

0.030

 W × D

2.9

0.029

1.3

0.282

1.3

0.286

 H × D

1.1

0.355

1.6

0.188

0.8

0.541

 W × H × D

0.2

0.916

0.5

0.766

0.3

0.891

2018

 Soil OM content

0.02

0.895

2.4

0.153

10.2

0.011

 Vascular plant cover

0.7

0.411

8.8

0.014

26.6

0.001

 Lichen cover

8.2

0.016

3.5

0.085

2.0

0.185

 Moss cover

5.2

0.046

7.6

0.018

2.8

0.125

 Date (D)

31.5

<0.001

60.8

<0.001

87.4

<0.001

 Warming (W)

13.2

0.006

13.9

0.004

1.6

0.239

 Herbivory reduction (H)

8.3

0.020

13.1

0.006

7.3

0.033

 W × H

0.4

0.534

1.3

0.280

1.7

0.238

 W × D

1.5

0.129

1.2

0.264

2.4

0.008

 H × D

1.3

0.215

1.3

0.223

0.4

0.944

 W × H × D

1.5

0.154

1.4

0.158

0.7

0.775

  1. Treatment effects on net ecosystem exchange (NEE800), gross primary production (GPP800), and ecosystem respiration (Re) were tested using repeated measures linear mixed models and Type I ANOVA (with two-sided significance tests), where the variance is allocated to explanatory variables in the order of their appearance. Soil organic matter (OM) content and cover of vascular plants, lichens, and mosses are continuous variables that describe the variation among the experimental plots prior to the establishment of the experiment. They were used in the models as covariates to remove plot-to-plot variation that might otherwise confound the treatment effects. Years were analyzed separately (N = 100 for 2017, N = 240 for 2018). Date was treated as a repeated measure, warming and herbivory reduction as fixed effects, and treatment block (not reported) as a random effect. F and P indicate F-statistics and P-values respectively; P < 0.05 are in bold.
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