Table 1 Mean (± SE) GHG emissions, VSWC, and EC measured weekly with their equivalent groundwater table depths and salinity treatments from soil cores collected from different land-use practices from two sites.
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Site A
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Site B
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CO2
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CH4
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N2O
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VSWC
|
EC
|
CO2
|
CH4
|
N2O
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VSWC
|
EC
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(mg m-2 d-1)
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(%)
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(mS cm-1)
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(mg m-2 d-1)
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(%)
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(mS cm-1)
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Land-use
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|
AC
|
1016 (±43) b
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2.57 (±0.83) b
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0.70 (±0.09) b
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48 (±0.42) a
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3.3 (±0.04) a
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784 (±41) b
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1.08 (±0.81) b
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1.20 (±0.15) b
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47 (±0.43) c
|
3.2 (±0.04) b
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PA
|
2348 (±123) a
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22.67 (±5.96) a
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5.35 (±0.76) a
|
47 (±0.39) a
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3.3 (±0.04) a
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1756 (±83) a
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2.36 (±0.76) a
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1.82 (±0.20) a
|
49 (±0.33) b
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3.4 (±0.04) a
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SRW
|
595 (±24) c
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0.43 (±0.18) b
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0.68 (±0.10) b
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47 (±0.48) a
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3.3 (±0.05) a
|
560 (±13) c
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0.01 (±0.01) c
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0.27 (±0.04) c
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50 (±0.18) a
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3.5 (±0.04) a
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Salinity
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S0
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1499 (±114) a
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19.2 (±5.91) a
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0.35 (±0.06) b
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43 (±0.29) b
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2.8 (±0.01) c
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1180 (±89) a
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1.79 (±0.85) a
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0.32 (±0.06) c
|
46 (±0.42) c
|
3.0 (±0.02) c
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S1
|
1333 (±123) b
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5.0 (±1.64) b
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3.27 (±0.68) a
|
50 (±0.13) a
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3.4 (±0.01) b
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1016 (±72) a
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0.45 (±0.15) a
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1.27 (±0.19) b
|
49 (±0.17) b
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3.4 (±0.02) b
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S2
|
878 (±98) c
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1.4 (±0.44) c
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3.11 (±0.49) a
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50 (±0.04) a
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3.7 (±0.01) a
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858 (±72) b
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1.21 (±0.71) a
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1.69 (±0.18) a
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50 (±0.06) a
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3.8 (±0.01) a
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Depth to GWT (week of measurement)
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2-cm (W1)
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1057 (±206) cd
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0.20 (±0.04) d
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0.28 (±0.08) d
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49 (±0.53) a
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3.3 (±0.07) a
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1042 (±149) cd
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0.19 (±0.06) d
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0.14 (±0.07) d
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51 (±0.29) a
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3.4 (±0.05) a
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5-cm (W2)
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1522 (±203) b
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2.07 (±0.56) cd
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0.47 (±0.09) cd
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49 (±0.49) a
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3.4 (±0.07) a
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1154 (±160) b
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1.67 (±0.65) b
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0.21 (±0.07) cd
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50 (±0.29) a
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3.5 (±0.06) a
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8-cm (W3)
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1489 (±196) ab
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15.07 (±4.14) b
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1.28 (±0.43) bcd
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49 (±0.55) b
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3.3 (±0.07) a
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1286 (±194) ab
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6.96 (±3.08) a
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0.29 (±0.11) bcd
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50 (±0.33) b
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3.5 (±0.06) a
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11-cm (W4)
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1981 (±291) a
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36.82 (±15.77) a
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2.56 (±0.94) abc
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48 (±0.61) c
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3.3 (±0.07) a
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1339 (±190) a
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0.99 (±0.38) bc
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0.82 (±0.23) abc
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49 (±0.41) c
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3.4 (±0.07) a
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14-cm (W5)
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1375 (±191) bc
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14.94 (±7.15) bc
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2.91 (±1.04) ab
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47 (±0.72) d
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3.3 (±0.08) b
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1095 (±120) bc
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0.27 (±0.08) cd
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1.11 (±0.26) ab
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48 (±0.52) d
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3.4 (±0.07) b
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17-cm (W6)
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1401 (±192) bc
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5.43 (±2.38) cd
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3.90 (±1.35) a
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47 (±0.84) e
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3.3 (±0.08) b
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1105 (±113) bc
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0.17 (±0.04) cd
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1.69 (±0.34) a
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48 (±0.62) e
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3.4 (±0.08) b
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20-cm (W7)
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1007 (±133) d
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2.04 (±0.78) d
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3.04 (±0.95) a
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46 (±0.87) f
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3.2 (±0.08) c
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678 (±56) d
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0.11 (±0.03) d
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1.83 (±0.32) a
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47 (±0.71) f
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3.3 (±0.08) c
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23-cm (W8)
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1093 (±125) d
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0.31 (±0.12) d
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2.88 (±0.77) a
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46 (±0.85) f
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3.2 (±0.08) c
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776 (±64) d
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-0.01 (±0.02) d
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2.00 (±0.36) a
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47 (±0.75) f
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3.3 (±0.08) c
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26-cm (W9)
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950 (±90) d
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0.14 (±0.05) d
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2.88 (±1.08) a
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46 (±0.91) f
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3.3 (±0.09) b
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822 (±50) d
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0.01 (±0.01) d
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1.77 (±0.31) a
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47 (±0.78) f
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3.4 (±0.08) b
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† Means within a column for sites, land-use, salinity, and depth to groundwater table followed by the same letter are not significantly different (p > 0.05) using Tukey HSD.
†† SE = standard error, GHG = greenhouse gas, VSWC = volumetric soil water content, EC = electrical conductivity, AC = annual crop, PA = pasture, SRW = short rotation willow, S0 = control, S1 = 6 mS cm-1, S2 = 12 mS cm-1, GWT = depth to groundwater table.
Table 2 Analysis of variance (ANOVA) with nested design and linear mixed-effects models for soil GHG emissions, VSWC, and EC measured weekly with their equivalent groundwater table depths and salinity treatments in core soils from three land-use practices from two sites.
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CO2
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CH4
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N2O
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VSWC
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EC
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Sources of variation
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df
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F stat
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p - value
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F stat
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p - value
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F stat
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p - value
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F stat
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p - value
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F stat
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p - value
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Site A
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Land-use
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2
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249.03
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<0.001 ***
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25.47
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<0.001 ***
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25.65
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<0.001 ***
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0.98
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0.411 ns
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1.57
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0.260 ns
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Salinity
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2
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11.10
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0.004 **
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7.63
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0.012 *
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13.88
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0.002 **
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306.99
|
<0.001 ***
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646.84
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<0.001 ***
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Depth to GWT
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8
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17.43
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<0.001 ***
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16.39
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<0.001 ***
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12.22
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<0.001 ***
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27.49
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<0.001 ***
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12.44
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<0.001 ***
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Site B
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Land-use
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2
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55.67
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<0.001 ***
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28.38
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<0.001 ***
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54.08
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<0.001 ***
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5.66
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0.026 *
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58.46
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<0.001 ***
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Salinity
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2
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5.59
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0.026 *
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2.71
|
0.069 ns
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46.69
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<0.001 ***
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18.78
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<0.001 ***
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427.49
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<0.001 ***
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Depth to GWT
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8
|
9.23
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<0.001 ***
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10.78
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<0.001 ***
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25.29
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<0.001 ***
|
29.44
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<0.001 ***
|
20.52
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<0.001 ***
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† *, **, *** Indicate there is a statistically significant difference at p ≤ 0.05, p ≤ 0.01 and p ≤ 0.001 level of significance, respectively; ns, is not significantly different (p > 0.05).
†† GHG = greenhouse gas, VSWC = volumetric soil water content, EC = electrical conductivity, GWT = depth to groundwater table.
Table 3 Permutation multivariate analysis of variance (PERMANOVA) test for GHG emissions under different groundwater salinity and water table levels in soil cores collected from three different land-use practices at two field sites.
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Site A
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Site B
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Sources of variation
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df
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Pseudo-F
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R2
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Pr (>F)
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Pseudo-F
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R2
|
Pr (>F)
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Land-use
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2
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35.91
|
0.23
|
0.001 ***
|
13.37
|
0.10
|
0.001 ***
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Salinity
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2
|
24.94
|
0.17
|
0.001 ***
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25.11
|
0.17
|
0.001 ***
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Groundwater table
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8
|
8.02
|
0.22
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0.001 ***
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13.41
|
0.31
|
0.001 ***
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† *, **, *** Indicate there is a statistically significant difference at p ≤ 0.05, p ≤ 0.01, and p ≤ 0.001 level of significance, respectively; ns, is not significantly different (p > 0.05).
†† GHG = greenhouse gas.
Table 4 Global warming potential (GWP) of CO2, CH4, and N2O (equivalent to CO2) of three different land-use practices from two sites.
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Land-use
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GWP (mg CO2-e m-2 d-1)
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Site A
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AC
|
1288.88 b
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PA
|
4509.89 a
|
SRW
|
808.47 c
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Site B
|
AC
|
1167.85 b
|
PA
|
2358.27 a
|
SRW
|
639.59 c
|
F = 15.19
p = 0.002 **
|
F = 112.73
p < 0.001 ***
|
|
† Means within a column for land-use followed by the same letter are not significantly different (p > 0.05) using Tukey HSD.
†† *, **, *** Indicate there is a statistically significant difference at p ≤ 0.05, p ≤ 0.01 and p ≤ 0.001 level of significance, respectively; ns, is not significantly different (p > 0.05).
††† GWP = global warming potential, AC = annual crop, PA = pasture, SRW = short rotation willow.