Table 1. An overview of Syrian Pinus brutia and Cupressus sempervirens study populations, incl. population type, geographic location, climatic conditions, population area, seed weight and percentage of seed viability, empty seeds and degraded embryos before the start of the experiment. View in new window/tab.
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Fig. 1. Sample locations of natural and afforested Pinus brutia and Cupressus sempervirens populations in Syria. Seed origins of the afforestations are marked with a star.

Table 2. Results of linear mixed-effects models performed for Pinus brutia. Models tested whether Population type (natural vs. afforested), Temperature (8/4 °C, 20/10 °C and 32/20 °C), Treatment (including, cold stratification, drought stress: –0.2 MPa and –0.4 MPa, salt stress: 50 mMol l–1 and 100 mMol l–1 and the “deionized water” as a control), and their interactions had a significant effect on seed germination. Population was used as a random effect and seed weight as ln-transformed.
Model/Treatment A: Cold stratification B: Drought stress C: Salt stress
Fixed effect d.f. F-value p-value d.f. F-value p-value d.f. F-value p-value
Population type 1 0.66 0.440 1 4.11 0.077 1 0.63 0.450
Temperature 2 255.23 <0.0001 2 729.47 <0.0001 2 926.59 <0.0001
Treatment 1 111.05 <0.0001 2 158.34 <0.0001 2 37.25 <0.0001
Seed weight 1 0.24 0.637 1 0.24 0.634 1 0.04 0.864
Population type × Temperature 2 9.97 0.0001 2 33.56 <0.0001 2 5.91 0.003
Population type × Treatment 1 0.89 0.346 2 15.21 <0.0001 2 2.75 0.065
Temperature × Treatment 2 12.84 <0.0001 4 43.15 <0.0001 4 15.09 0.0001
Population type × Temperature × Treatment 2 0.06 0.935 4 2.90 0.021 4 0.938 0.441
Bold numbers indicate significant effects (P < 0.05).
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Fig. 2. Interaction plots showing germination percentages of natural (left) and afforested (right) Pinus brutia populations across three different temperature regimes and treatments. Note that germination percentage is shown as not arcsine – transformed. Control = deionized water. Drought stress was tested at levels of –0.2 MPa and –0.4 MPa, and salt stress at concentrations of 50 mMol l–1 and 100 mMol l–1.

Table 3. Results of linear mixed-effects models performed for Cupressus sempervirens. Models tested whether Population type (natural vs. afforested), Temperature (8/4 °C, 20/10 °C and 32/20 °C), Treatment (including, cold stratification, drought stress: –0.2 MPa and –0.4 MPa, salt stress: 50 mMol l–1 and 100 mMol l–1 and the “deionized water” as a control), and their interactions had a significant effect on seed germination. Population was used as a random effect and seed weight as ln-transformed.
Model/Treatment A: Cold stratification B: Drought stress C: Salt stress
Fixed effect d.f. F-value p-value d.f. F-value p-value d.f. F-value p-value
Population type 1 1.81 0.226 1 0.67 0.448 1 0.10 0.758
Temperature 2 85.43 <0.0001 2 344.37 <0.0001 2 230.52 <0.0001
Treatment 1 3.79 0.048 2 78.69 <0.0001 2 56.08 <0.0001
Seed weight 1 1.96 0.219 1 1.34 0.298 1 0.39 0.557
Population type × Temperature 2 0.01 0.986 2 5.38 <0.001 2 7.34 <0.001
Population type × Treatment 1 28.91 <0.0001 2 0.23 0.790 2 4.29 0.014
Temperature × Treatment 2 4.37 0.014 4 7.21 <0.0001 4 6.21 0.0001
Population type × Temperature × Treatment 2 8.93 <0.001 4 3.42 0.009 4 0.34 0.846
Bold numbers indicate significant effects (P < 0.05).
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Fig. 3. Interaction plots showing germination percentages of natural (left) and afforested (right) Cupressus sempervirens populations across three different temperature regimes and treatments. Note that germination percentage is shown as not arcsine – transformed. Control = deionized water. Drought stress was tested at levels of –0.2 MPa and –0.4 MPa, and salt stress at concentrations of 50 mMol l–1 and 100 mMol l–1.

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Fig. 4. Relationship between mean germination percentage and annual precipitation and mean annual temperature per population of Pinus brutia and Cupressus sempervirens, respectively (natural populations: empty triangles; afforested populations: solid triangles).