Figure 1.
Thuja seedlings from the nursery to the field: (i) at lifting time in the nursery (December 10, 2019), (ii) after extraction from the container showing: [a] shoots, [b] collar, [c] root plug, (iii) after outplanting in the field (July 15, 2020).
Figure 2.
Average monthly rainfall (mm) during the entire planting season (October 1st, 2019 to October 30th, 2020) collected in the meteorological station of Oued Beht, Khémisset. Note how the plantation window (December 12th, 2019) was decided after the occurrence of more than 100 mm cumulative rainfall.
Figure 3.
Variation of daily rainfall (mm) and temperatures (Tmax and Tmin (°C)) from April 1st to October 30th, 2020. It is noteworthy that the dry period (from mid-May to mid-October 2020) coincided with the hottest season; data collected in the meteorological station of Oued Beht, Khemisset.
Figure 4.
Profile of a forest bench showing how seedlings were planted on the bench ridges.
Table 1.
General morphological traits of thuja seedlings at lifting time in the nursery (n = 1734).
| Attributes | Min | Max | Mean |
|---|---|---|---|
| Shoot height (cm) | 4.01 | 53.01 | 20.58 ±8.25 |
| Collar diameter (mm) | 1.07 | 9.11 | 3.37 ±0.78 |
| Sturdiness index | 2.26 | 10.69 | 5.92 ± 1.48 |
Table 2.
Correlations between different initial morphological traits of thuja seedlings.
| Regression model | n | p-value | R2 |
|---|---|---|---|
| H0= -9.507 + 8.896*D0 | 1734 | p < 0.0001 | 0.72 |
| H0 = -8.323 + 4.875*SI0 | 1734 | p < 0.0001 | 0.76 |
| SI0 = 2.608 + 0.978*D0 | 1734 | p < 0.0001 | 0.26 |
Table 3.
Initial morphological classes of thuja seedlings at outplanting time using the K-means method. IMC: Initial morphological class.
| IMC | Seedling size | Centroid | Class weight | lntra-class variance | ||
|---|---|---|---|---|---|---|
| H0 (cm) | D0 (mm) | SI0 (cm mm−1) | ||||
| A | Small | 10.8 | 2.52 | 4.35 | 513 | 6.333 |
| B | Medium | 18.25 | 3.31 | 5.57 | 460 | 5.100 |
| C | Large | 24.93 | 3.76 | 6.7 | 435 | 4.641 |
| D | Extra-large | 32.75 | 4.26 | 7.74 | 326 | 12.477 |
| Total | 1734 | |||||
Figure 5.
Survival rates of Tetraclinis articulata seedlings during the dry period of 2020 showing a remarkable drop between July 15 and August 15, 2020.
Figure 6.
The survival rate of thuja seedlings within initial morphological classes among the 51 observed plots (A: Small, B: Medium, C: Large, D: Extra-large seedlings). Different letters among treatments denote significant differences (p < 0.05) according to Fisher LSD test (n = 204).
Table 4.
Logistic regression model parameters of the survival and initial morphological traits of thuja seedlings: shoot height H0 (cm), collar diameter D0 (mm) and sturdiness index SI0 (cm mm−1) (n = 1734). SE: standard error; OR: odds ratio; CI: confidence interval.
| Source | β | μ | SE | Wald’s χ2 | Pr > χ2 | OR | 95% CI for OR | |
|---|---|---|---|---|---|---|---|---|
| Lower | Upper | |||||||
| Constant | -0.158 | 0.113 | 1.946 | 0.163 | ||||
| H0 (cm) | 0.008 | 0.005 | 2.371 | 0.124 | 1.008 | 0.998 | 1.018 | |
| Constant | -1.693 | 0.197 | 73.789 | <0.0001 | ||||
| D0 (mm) | 0.522 | 3.24 | 0.059 | 78.966 | <0.0001 | 1.685 | 1.502 | 1.891 |
| Constant | 0.475 | 0.179 | 6.991 | 0.008 | ||||
| SI0 (cm mm1) | -0.080 | 5.93 | 0.029 | 7.528 | 0.006 | 0.924 | 0.873 | 0.978 |
Table 5.
Comparison of shoot height and collar diameter relative growth rates and sturdiness index variation within the initial morphological classes of thuja seedlings using the Kruskal-Wallis test with a 5% significance level. The means are separated by the Dunn procedure. Values followed by different letters within the same column are significantly different. IMC: Initial morphological class.
| IMC | Obs. | RGR(H) (cm/cm/month) | RGR(D) (mm/mm/month) | Sturdiness index variation | ||
|---|---|---|---|---|---|---|
| Sl0 | Sl1 | SI1/SI0 | ||||
| A | 200 | 0.033 ± 0.017 c | 0.029 ± 0.017 a | 4.250 a | 4.449 a | 1.061 ± 0.171 c |
| B | 200 | 0.028 ± 0.018 b | 0.028 ± 0.018 a | 5.472 b | 5.442 b | 1 ± 0.147 b |
| C | 200 | 0.023 ± 0.013 ab | 0.030 ± 0.014 a | 6.696 c | 6.649 c | 0.938 ± 0.127 a |
| D | 200 | 0.02 ± 0.014 a | 0.031 ± 0.017 a | 7.393 d | 6.215 d | 0.911 ± 0.118 a |
Figure 7.
Gravimetric soil moisture content Hg (%) pattern within soil depth (10, 30, 50, 70 and 90 cm) during drought season (May to October 2020).
Figure 8.
Soil moisture content Hg (%) variation as affected by soil depth (cm) at the end of the drought season (September 15, 2020). Different letters among treatments denote significant differences (p < 0.05) according to Fisher LSD test (n = 100).
Table 6.
Logistic regression model parameters of the survival and rooting depth (cm) (n = 62) of thuja seedlings. SE: standard error; OR: odds ratio; CI: confidence interval; Rd: rooting depth (cm).
| Source | β | μ | SE | Wald’s χ2 | Pr > χ2 | OR | 95% CI for OR | |
|---|---|---|---|---|---|---|---|---|
| Lower | Upper | |||||||
| Constant | -5.428 | 1.542 | 12.394 | <0.0001 | ||||
| Rd (cm) | 0.094 | 57.74 | 0.026 | 13.284 | <0.0001 | 1.1 | 1.045 | 1.156 |
Figure 9.
Relationship between initial collar diameter and rooting depth of thuja seedlings after 11 months of outplanting in the field.
Figure 10.
Relationship between initial shoot height and rooting depth of thuja seedlings after 11 months of outplanting in the field.
Figure 11.
Relationship between initial sturdiness index and rooting depth of thuja seedlings after 11 months of outplanting in the field.