Table 5.
Pearson correlation coefficients (r) between N or P content in live fine root mass and selected abiotic and biotic factors, across all genotypes and for each genotype, in 14 year-old hybrid poplar plantations.
| Factors correlated to N content (kg/ha) in live fine root biomass | r | P-value | Factors correlated to P content (kg/ha) in live fine root biomass | r | P-value |
|---|---|---|---|---|---|
| Across all genotypes (n = 27) | Across all genotypes (n = 27) | ||||
| Live fine root mass (kg/ha) | 0.97 | <0.0001 | Live fine root mass (kg/ha) | 0.74 | <0.0001 |
| Leaf litter P (%) | −0.62 | 0.0005 | Leaf litter N (%) | −0.53 | 0.005 |
| Leaf Litter N (%) | −0.57 | 0.002 | Leaf litter P (%) | −0.40 | 0.04 |
| Soil base saturation (%) | −0.50 | 0.008 | Genotype DN × M (n = 9) | ||
| Soil CEC (meq/100 g) | −0.50 | 0.008 | Soil clay content (%) | 0.83 | 0.006 |
| Soil NO3 supply (µg/10 cm2/42d) | −0.49 | 0.009 | Soil Ca supply (µg/10 cm2/42d) | 0.71 | 0.03 |
| Leaf litter mass remaining after 1 yr (%) | 0.48 | 0.01 | Soil P supply (µg/10 cm2/42d) | 0.70 | 0.04 |
| Site elevation (m) | 0.47 | 0.01 | Leaf litter P (%) | 0.70 | 0.04 |
| Soil clay content (%) | −0.46 | 0.01 | Genotype D × N (n = 9) | ||
| Soil bulk density (g/cm3) | −0.46 | 0.02 | Live fine root mass (kg/ha) | 0.85 | 0.004 |
| Soil sand content (%) | 0.46 | 0.02 | Soil silt content (%) | 0.75 | 0.02 |
| Soil pH | −0.46 | 0.02 | Soil sand content (%) | −0.68 | 0.04 |
| Soil C:N ratio | 0.43 | 0.02 | Genotype M × B (n = 9) | ||
| Genotype DN × M (n = 9) | Live fine root mass (kg/ha) | 0.95 | 0.0001 | ||
| Live fine root mass (kg/ha) | 0.88 | 0.002 | Leaf litter N (%) | −0.77 | 0.02 |
| Genotype D × N (n = 9) | Soil CEC (meq/100 g) | −0.77 | 0.02 | ||
| Live fine root mass (kg/ha) | 0.98 | <0.0001 | Soil pH | −0.77 | 0.02 |
| Leaf litter mass remaining after 1 yr (%) | 0.79 | 0.01 | Soil base saturation (%) | −0.73 | 0.03 |
| Site elevation (m) | 0.76 | 0.02 | Soil NO3 supply (µg/10 cm2/42d) | −0.70 | 0.04 |
| Soil NO3 supply (µg/10 cm2/42d) | −0.66 | 0.05 | Soil NH4 supply (µg/10 cm2/42d) | 0.70 | 0.04 |
| Genotype M × B (n = 9) | Site elevation (m) | 0.67 | 0.05 | ||
| Live fine root mass (kg/ha) | 0.99 | <0.0001 | Leaf litter P (%) | −0.67 | 0.05 |
| Leaf litter P (%) | −0.85 | 0.004 | Soil sand content (%) | 0.66 | 0.05 |
| Soil sand content (%) | 0.82 | 0.007 | |||
| Leaf litter N (%) | −0.80 | 0.009 | |||
| Soil base saturation (%) | −0.74 | 0.02 | |||
| Soil C:N ratio | 0.72 | 0.03 | |||
| Soil CEC (meq/100 g) | −0.71 | 0.03 | |||
| Leaf litter Ca (%) | 0.71 | 0.03 | |||
| Soil clay content (%) | −0.69 | 0.04 | |||
| Soil P supply (µg/10 cm2/42d) | −0.67 | 0.05 | |||
| Soil NO3 (µg/10 cm2/42d) | −0.66 | 0.05 | |||
Only correlations with p ≤ 0.05 are shown. Mean values of N and P content in live fine root mass and of soil nutrient supply rate (across 3 sampling periods) were used in the analysis.