Table 1.
Description of the three experiments used for the comparative approach
| Experiment 1 | Experiment 2 | Experiment 3 | |||
|---|---|---|---|---|---|
| Environmental conditions | Type | Outdoor plantations | Outdoor plantations | Greenhouse | |
| Location | Orléans (ORL), France | Echigey (ECH) and Saint-Cyr-en-Val (SCV), France | Echigey (ECH), Saint- Cyr-en-Val (SCV), and Guémené (GMN), France | Nancy, France | |
| Treatments studied | Water availability | Pedoclimatic conditions (mainly water availability and soil fertility) | Pedoclimatic conditions (mainly water availability and soil fertility) | Water availability | |
| Number of treatment conditions | 2 | 2 | 3 | 3 | |
| Treatment conditions | Irrigated (ORLWW, favorable) versus non-irrigated (ORLWD, unfavorable) | ECH (favorable) versus SCV (unfavorable) | ECH (favorable) versus SCV or GMN (unfavorable) | Well-watered (WW, favorable) versus water deficit (WD, unfavorable) or rewatered (WD- RW, unfavorable) | |
| General characterization | ORLWW: Pre‐dawn leaf water potential above –0.20 MPa | ECH: Summer soil VWC >40% (fertile site) | ECH: Summer soil VWC >40% (fertile site) | WW: Soil REW maintained close to 100% | |
| ORLWD: Pre‐dawn leaf water potential of –0.75 MPa at the drought peak | SCV: Summer soil VWC <20% (poor site) | SCV: Summer soil VWC <20% (poor site) | WD: Soil REW maintained at 20% during 2 weeks | ||
| GMN: Summer soil VWC <20% (poor site) | WD-RW: Soil REW maintained at 20% during 8 days followed by rewatering at field capacity for 6 days | ||||
| Plantation design | Culture | Coppice | Coppice | Coppice | Potted cuttings |
| Species | P. deltoides × P. nigra | P. deltoides × P. nigra | P. deltoides × P. nigra and P. trichocarpa | ||
| Number of genotypes | 8 | 56 | 1 | 4 | |
| Design | Randomized multiclonal blocks | Randomized multiclonal blocks | Monoclonal blocks | Randomized multiclonal blocks | |
| Number of blocks | 5 | 10 | 1 | 3 | |
| Number of individuals per genotype per block | 3 | 1 | 10 | 6 | |
| Plantation year | 2006 | 2009 (ECH), 2010 (SCV) | 2009 (ECH, GMN), 2010 (SCV) | 2008 | |
| Coppice year | 2007, 2008 | 2010 (ECH), 2011 (SCV) | 2010 (ECH, GMN), 2011 (SCV) | ||
| Sampling year | 2008 | 2010 (ECH), 2011 (SCV) | 2010 (ECH, GMN), 2011 (SCV) | 2008 | |
| Age at sampling time | 3 years | 2 years | 2 years | 3 months | |
| Previously highlighted effects | Main shoot annual dry mass | G×E ns, G*, E** | G×E***, G***, E*** | ||
| Relative growth rate in height | G×E ***, G*, E** | G×E ns, G***, E*** | |||
| References | Fichot et al., 2010, 2011 | Toillon et al., 2013a | Toillon et al., 2013b | Bizet et al., 2015; Lafon- Placette et al., 2018 | |
REW, Relative extractible water; SAM, shoot apical meristem; VWC, volumetric water content. Effect of growing environments was evaluated with an ANOVA test (G, genotype effect; E, environment effect for growth conditions; G×E, interaction between genotype and environment). Levels of significance: *P<0.05, **P<0.01, ***P<0.001; ns, non-significant. The corresponding references for these data are indicated.