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Fig. 1. Schematic figure of silver birch seedlings in climate-controlled closed-top chambers in 2002. A) randomized placement of seedling-trays in each chamber; B) location of chambers in the field.

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Fig. 2. Placement of differently treated silver birch seedlings in the built environments in 2003 (figure is not drawn to scale). Within each climate treatment, all the seedlings were located randomly, and their positions re-randomized each week. The distance between the seedlings was 20 cm.

Table 1. Summary of cross tabulations for survived and dead seedlings. The term “survived” refers to overwintered seedlings and “dead” to seedlings that were winterkilled or suffered from broken stems. The percentage (%) of each group indicates the proportion of all the 384 seedlings in the 2003 experiment.
Treatment
  Amb. T and amb. CO2 Amb. T and elev. CO2 Elev. T and amb. CO2 Elev. T and elev. CO2 Total
  Number % Number % Number % Number % Number %
Survived 32 8.3 46 12.0 41 10.7 47 12.2 166 43.2
Dead 64 16.7 50 13.0 55 14.3 49 12.8 218 56.8
Total 96 25.0 96 25.0 96 25.0 96 25.0 384 100.0
 
  Fertilized     Unfertilized     Total
  Number %     Number %     Number %
Survived 90 23.4     76 19.8     166 43.2
Dead 102 26.6     116 30.2     218 56.8
Total 192 50.0     192 50.0     384 100.0
 
  Control 25% defoliated 50% defoliated 75% defoliated Total
  Number % Number % Number % Number % Number %
Survived 49 12.8 41 10.7 40 10.4 36 9.4 166 43.2
Dead 47 12.2 55 14.3 56 14.6 60 15.6 218 56.8
Total 96 25.0 96 25.0 96 25.0 96 25.0 384 100.0
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Fig. 3. Absolute height increment (cm) of silver birch seedlings during the growing season 2003. The plot results are based on untransformed data, where mean values of different treatment combinations with the standard errors are presented. The trend line is based on the least squares means (LS means) provided by SAS/MIXED. Abbreviations: Amb. T = ambient temperature; Elev. T = elevated temperature; Amb. CO2 = ambient CO2; Elev. CO2 = elevated CO2.

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Fig. 4. Root: shoot ratios (biomass of roots in proportion to biomass of stems + leaves) of silver birch seedlings in different treatment combinations at the end of the experiment. The plot results are based on untransformed data, where mean values of different treatment combinations with the standard errors are presented. The trend line is based on the least squares means (LS means) provided by SAS/MIXED. Abbreviations: Amb. T = ambient temperature; Elev. T = elevated temperature; Amb. CO2 = ambient CO2; Elev. CO2 = elevated CO2.