Table 2. Regression analysis of the methanol flux a.
| simple linear regression |
multiple linear regression |
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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Half-hourly |
Daily Average |
Half-hourly |
Daily Average |
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| N | r | p | N | r | p | partial correlation | tolerance | p | partial correlation | tolerance | p | |||||||
| NEE | 5503 | −0.44 | *** | 228 | −0.08 | ns | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | |
| latent heat flux | 5503 | 0.63 | *** | 219 | 0.71 | *** | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | |
| sensible heat flux | 5503 | 0.32 | *** | 235 | −0.01 | ns | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | |
| GAI | 5503 | -- | -- | 321 | 0.39 | *** | -- | -- | -- | -- | -- | -- | 0.10 | (0.11) | 0.64 | (0.64) | ns | (ns) |
| dGAI | 5503 | -- | -- | 321 | 0.53 | *** | -- | -- | -- | -- | -- | -- | 0.12 | (0.18) | 0.51 | (0.51) | ns | (*) |
| SWC | 5503 | −0.36 | *** | 321 | −0.60 | *** | −0.12 | (0.00) | 0.69 | (0.59) | *** | (ns) | 0.00 | (0.18) | 0.51 | (0.46) | ns | (*) |
| fdif | 5503 | −0.43 | *** | 321 | −0.25 | *** | 0.10 | (0.11) | 0.32 | (0.32) | *** | (***) | 0.20 | (0.14) | 0.21 | (0.21) | * | (ns) |
| b gsurf | 3954 | 0.34 | *** | 219 | 0.35 | *** | 0.08 | (0.15) | 0.79 | (0.75) | *** | (***) | 0.00 | (0.15) | 0.79 | (0.73) | ns | (ns) |
| VPD | 5503 | 0.50 | *** | 321 | 0.68 | *** | −0.25 | (-0.17) | 0.20 | (0.19) | *** | (***) | 0.04 | (0.06) | 0.14 | (0.14) | ns | (ns) |
| b Tsoil | 5503 | 0.45 | *** | 321 | 0.72 | *** | −0.06 | (0.00) | 0.24 | (0.23) | *** | (ns) | 0.01 | (0.11) | 0.12 | (0.11) | ns | (ns) |
| b Tair | 5503 | 0.60 | *** | 321 | 0.82 | *** | 0.32 | (0.19) | 0.10 | (0.08) | *** | (***) | 0.29 | (0.11) | 0.07 | (0.06) | *** | (ns) |
| b PAR | 5503 | 0.60 | *** | 321 | 0.63 | *** | 0.36 | (0.39) | 0.29 | (0.29) | *** | (***) | 0.28 | (0.16) | 0.14 | (0.13) | *** | (*) |
| methanol VMR | 5503 | 0.41 | *** | 321 | 0.80 | *** | -- | (0.30) | -- | (0.52) | -- | (***) | -- | (0.49) | -- | (0.28) | -- | (***) |
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| whole model r2 | 0.52 (0.56) | 0.74 (0.80) | ||||||||||||||||
Correlation coefficients of a simple linear regression analysis and partial correlations, tolerance and significance of a multiple linear regression analysis, using half-hourly and daily average values of net ecosystem CO2 exchange (NEE), latent and sensible heat flux, green plant area index (GAI), change in green plant area index (dGAI), soil water content (SWC) at 0.05 m soil depth, fraction of diffuse radiation (fdif), surface conductance (gsurf), vapor pressure deficit (VPD), soil temperature (Tsoil) at 0.05 m soil depth, air temperature (Tair), photosynthetically active radiation (PAR) and methanol volume mixing ratio (VMR) as independent variables. For the multiple regression analysis 3154 half hourly and 169 daily average data points were used, respectively. Numbers in parenthesis refer to the analysis with the methanol concentration included in the multiple regression equation. Management events were excluded from the analysis.
number of cases>
correlation coefficient
significance level:
…p < 0.05
…p < 0.001, ns…not significant
…linearized