McAbee et al. Online Resources

Online Resource 1. Variation in soil temperature at 0-15-cm depths between May 15 and September 12, 2014 in A. cristatum monoculture plots (panel A) and native sagebrush steppe vegetation plots (panel B). Data collection coincided with Rsoil measurements, and symbols represent means  SE. Data from mid-June are missing due to equipment failure.

Time Interval / Vegetation / Campaign Date / Overall F / Overall P / Post-Hoc Comparison / Tukey's P
Dawn / Native / 1-Jul / 12.22 / 0.0077 / AMB > SUM / 0.0062
29-Jul / 25.49 / 0.0012 / AMB > SUM / 0.0010
WIN > SUM / 0.0133
CWG / 4-Jun / 12.45 / 0.0073 / AMB > WIN / 0.0095
SUM > WIN / 0.0152
12-Aug / 20.61 / 0.0177 / AMB > SUM / 0.0164
WIN > SUM / 0.0488
Mid-Day / Native / 1-May / 5.5 / 0.0440 / All two-way P > 0.05
15-May / 5.71 / 0.0409 / WIN > SUM / 0.0365
18-Jun / 98.53 / 0.0018 / WIN > AMB / 0.002
WIN > SUM / 0.0033
29-Jul / 15.64 / 0.0042 / SUM > AMB / 0.0049
SUM > WIN / 0.0109
12-Aug / 5.94 / 0.0378 / SUM > AMB / 0.0442
CWG / 15-May / 6.41 / 0.0324 / WIN > SUM / 0.0335
4-Jun / 31.05 / 0.0007 / WIN > SUM / 0.0011
WIN > AMB / 0.0013
18-Jun / 33.96 / 0.0087 / WIN > SUM / 0.0096
WIN > AMB / 0.0149
1-Jul / 8.73 / 0.0167 / WIN > AMB / 0.0170
WIN > SUM / 0.0490
29-Jul / 6.16 / 0.0351 / SUM > AMB / 0.0322
Evening / CWG / 12-Sep / 5.62 / 0.0422 / SUM > WIN / 0.0395

Online Resource 2. Summary ANOVA table for the effects of irrigation (ambient, +summer, +winter) on NEE within each campaign date and within vegetation treatment (A. cristatum and native sagebrush steppe), with post-hoc Tukey comparisons. Only dates at which an overall effect (P < 0.05) was detected are recorded.

Online Resource 3. Dawn, mid-day, and evening Anet of the three most abundant plant species (A. cristatum, H. boreale, and A. tridentata) averaged across the growing season. Letters indicate which species groups are significantly different from others (P < 0.05) within a single diurnal interval. Error bars represent one standard error of the mean. Because Anet means did not vary significantly across the growing season, or between vegetation and irrigation treatments, these data represent means across those variables. Here, greater dark respiration (Anet measured at dawn interval) is indicated by a more negative Anet.

Online Resource 4. Seasonal variation in Anet of the three most abundant plant species in native vegetation plots (A. cristatum, a-c; H. boreale, d-f; A. tridentata, g-i).

Online Resource 5. Variation in leaf-level Anet with soil volumetric water content at dawn (top panels) and midday (bottom panels) among ambient, summer, and winter plots. Soil moisture data are averaged across 0.2-1.0 m depths. Panels A and B present Anet averaged across all plant species available at the time of each measurement campaign. Panels C and D present Anet for A. tridentata shrubs only (the dominant plant in each plot). Because moisture sensors were located only in native vegetation plots, Anet data are presented only for native vegetation plots (no data presented for A. cristatum monoculture plots). No regression lines are displayed because R2 values were less than 0.31 and P values were greater than 0.21 for all fits.

Time Interval / Vegetation / Campaign Date / Overall F / Overall P / Post-Hoc Comparison / Tukey's P
Dawn * / Native / 1-Jul / 11.71 / 0.0085 / WIN > AMB / 0.0086
SUM > AMB / 0.0277
29-Jul / 39.27 / 0.0004 / SUM > WIN / 0.0017
SUM > AMB / 0.0004
CWG / 4-Jun / 20.31 / 0.0021 / WIN > SUM / 0.0021
WIN > AMB / 0.0089
1-Jul / 8.61 / 0.0173 / WIN > AMB / 0.0152
15-Jul / 9.16 / 0.0150 / SUM > AMB / 0.0123
29-Jul / 9.90 / 0.0126 / SUM > WIN / 0.0448
SUM > AMB / 0.0121
Mid-Day / Native / 4-Jun / 11.33 / 0.0092 / WIN > SUM / 0.0364
WIN > AMB / 0.0087
15-Jul / 44.46 / 0.0003 / SUM > WIN / 0.0015
SUM > AMB / 0.0002
29-Jul / 16.51 / 0.0036 / SUM > WIN / 0.0118
SUM > AMB / 0.0039
CWG / 15-Jul / 34.14 / 0.0012 / SUM > WIN / 0.0019
SUM > AMB / 0.0023
Evening *† / Native / 29-Jul / 52.08 / 0.0002 / SUM > WIN / 0.0006
SUM > AMB / 0.0002
CWG / 29-Jul / 32.09 / 0.0006 / SUM > WIN / 0.0027
SUM > AMB / 0.0006

* Excludes data from campaign dates specified in Table 4 footnotes.

† SUM Rsoil marginally greater than AMB Rsoil in Native (P = 0.0543) and CWG plots (P = 0.0513) in July

Online Resource 6. Summary ANOVA table of the effects of irrigation treatments (ambient, +summer, +winter) on across-species Rsoil within each campaign date and within vegetation treatment (A. cristatum and native sagebrush steppe), with post-hoc Tukey comparisons. Only dates at which an overall effect (P < 0.05) was detected are recorded.

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