Appendices (for Online Publication Only)

Appendix 1. Light availability measured as mean photosynthetic photon flux density (PPFD) during the measurements of net ecosystem CO2exchange on each sampling date at the dry heath lichen, mesic birch hummock and wet sedge meadow ecosystems over the snow-free season.

Appendix 2. Repeated Measures Analysis of Variance (RM-ANOVA) of Carbon Dioxide Flux Components (NEE, GEP, ER and SR) Between Sampling Dates (time) and Among Tundra Ecosystems for the Three Phases of the Snow-Free Season

Effect / df / F / P
Net Ecosystem Exchange
Spring Thaw1 / Ecosystem / 2, 30 / 8.32 / 0.0037
Plot [Ecosystem] / 15, 30 / 1.30 / 0.26
Time / 2, 30 / 20.90 / <0.0001
Time*Ecosystem / 4, 30 / 4.50 / 0.0058
Summer / Ecosystem / 2, 180 / 6.58 / 0.0089
Plot [Ecosystem] / 15, 180 / 16.12 / <0.0001
Time / 12, 180 / 21.63 / <0.0001
Time*Ecosystem / 24, 180 / 5.55 / <0.0001
Fall Senescence / Ecosystem / 2, 15 / 1.31 / 0.30
Plot [Ecosystem] / 15, 15 / 1.14 / 0.40
Time / 1, 15 / 34.37 / <0.0001
Time*Ecosystem / 2, 15 / 5.60 / 0.015
Gross Ecosystem Photosynthesis
Spring Thaw1 / Ecosystem / 2, 30 / 3.89 / 0.043
Plot [Ecosystem] / 15, 30 / 3.07 / 0.0043
Time / 2, 30 / 4.29 / 0.023
Time*Ecosystem / 4, 30 / 8.72 / <0.0001
Summer / Ecosystem / 2, 180 / 4.45 / 0.030
Plot [Ecosystem] / 15, 180 / 45.47 / <0.0001
Time / 12, 180 / 11.78 / <0.0001
Time*Ecosystem / 24, 180 / 2.00 / 0.0057
Fall Senescence / Ecosystem / 2, 15 / 7.51 / 0.0055
Plot [Ecosystem] / 15, 15 / 2.73 / 0.030
Time / 1, 15 / 107.23 / <0.0001
Time*Ecosystem / 2, 15 / 9.03 / 0.0027
Ecosystem Respiration
Spring Thaw1 / Ecosystem / 2, 33 / 31.85 / <0.0001
Plot [Ecosystem] / 12, 33 / 6.33 / <0.0001
Time / 2, 33 / 34.03 / <0.0001
Time*Ecosystem / 4, 33 / 1.89 / 0.13
Summer / Ecosystem / 2, 183 / 22.03 / <0.0001
Plot [Ecosystem] / 12, 183 / 27.40 / <0.0001
Time / 12, 183 / 11.40 / <0.0001
Time*Ecosystem / 24, 183 / 6.85 / <0.0001
Fall Senescence / Ecosystem / 2, 18 / 38.56 / <0.0001
Plot [Ecosystem] / 12, 18 / 0.96 / 0.52
Time / 1, 18 / 9.54 / 0.0063
Time*Ecosystem / 2, 18 / 0.22 / 0.81
Soil Respiration
Spring Thaw1 / Ecosystem / 2, 30 / 31.53 / <0.0001
Plot [Ecosystem] / 15, 30 / 7.41 / <0.0001
Time / 2, 30 / 43.03 / <0.0001
Time*Ecosystem / 4, 30 / 18.26 / <0.0001
Summer / Ecosystem / 2, 180 / 19.55 / <0.0001
Plot [Ecosystem] / 15, 180 / 27.56 / <0.0001
Time / 12, 180 / 8.19 / <0.0001
Time*Ecosystem / 24, 180 / 4.95 / <0.0001
Fall Senescence / Ecosystem / 2, 15 / 41.69 / <0.0001
Plot [Ecosystem] / 15, 15 / 2.82 / 0.027
Time / 1, 15 / 15.21 / 0.0014
Time*Ecosystem / 2, 15 / 19.55 / <0.0001

1The first three sampling dates were excluded from the analysis because there were no data for the wet sedge meadow and RM-ANOVA does not permit missing values.

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