Table 1. Description of the trial sites within each country. The trial Id consists of country where Den = Denmark and Swe = Sweden, site type where F = Forest land and A = Agricultural land and parallel trial series number within country. TS = degree days based on daily mean temperatures >5 °C (Perttu and Moren 1995) and pH = soil acidity.
Trial id Name Site type Planted
year 		Latitude, Longitude Alt
m 		TS Degree
days 		pH
Den_A1 Give Agricultural 2012 55°83´N, 09°16´E 75 1552
Den_F1 Lournkaer_Nord Forest 2012 56°72´N, 10°20´E 1 1567
Den_F2 Lournkaer-Syd Forest 2012 56°70´N, 10°14´E 30 1542
Swe_A1 Sturup Agricultural 2010 55°56´N, 13°38´E 120 1466 5.9
Swe_F1 Matteröd Forest 2010 56°11´N, 13°62´E 114 1438 4.2
Swe_A2 Remningstorp Agricultural 2010 58°26´N, 13°37´E 133 1291 5.1
Swe_F2 Toftaholm Forest 2010 56°99´N, 14°05´E 162 1344 4.8
Swe_A3 Harg Agricultural 2010 60°09´N, 18°25´E 20 1276 7.9
Swe_F3 Karön Forest 2010 60°29´N, 18°36´E 25 1267 7.8
Swe_A4 Ed Agricultural 2011 63°25´N, 17°23´E 75 1039 5.2
Swe_F4 “Pommac” Forest 2011 63°11´N, 17°27´E 265 888 4.9
Swe_A5 Degerbyn Agricultural 2011 64°78´N, 20°81´E 20 993 4.9
Swe_F5 Degerbyn Forest 2011 64°78´N, 20°81´E 20 992 4.4

Fig. 1. Location of the trials. The parallel trials i.e. trials with similar climatic conditions and including the same test material are encircled. “X” represents forest land and the balloon symbol represents agricultural land.

Table 2. Description of material groups per species, deployment areas and number of clones per group. “STT” = SweTree Technologies.
Species Main deployment area Description Clones
N
Group name
Hybrid aspen
Swe_S_Com S. Sweden Genotypically seleced clones for commercial use 15
Swe_S_New S. Sweden An additional genotypic selection in trials where Swe_S_Com was tested 11
Swe_N N. Sweden Phenotypic selection 23
Finl S. Finland Phenotypic selection 23
Latv Latvia Phenotypic selection 22
Germ N. Germany Phenotypic selection 15
Poplar
Swe_S_Com S. Sweden Genotypically selected clones for commercial use (P. trichocarpa or
P. maximowiczii × P. trichocarpa). Includes clone OP42 		16
Swe_N N. Sweden Phenotypic selection (P. trichocarpa) 23
Swe_STT_C C. Sweden Phenotypic selection STT, (P. trichocarpa) 5
Swe_STT_N N. Sweden Phenotypic selection STT, (P. trichocarpa) 9
Icel Iceland Phenotypic selection, (P. trichocarpa) 7
Be Belgium Phenotypic selection, (P. deltoides x P. trichocarpa) 43
Ital Italy Commercial clones (AF2, AF8, AF13, Monviso, AF18, AF24, AF28) 7
EU_Com C. Europe Commercial clones (Grimminge, Koster and Muur). 3
Norw Norway Phenotypic selection, (P. trichocarpa) 4
Sum of clones 226
Table 3. Distribution of the number of hybrid aspen and poplar clones tested on different material groups and sites. See Table 2 for explanation of material groups.
Trial id Material groups of Hybrid aspen Material groups of Poplar
Swe_S
_Com 		Swe_S
_New 		Swe
_N 		Finl Latv Germ Swe_S
_Com 		Swe
_N 		Swe
_STT_C 		Swe
_STT_N 		Icel Be Ital EU
_Com 		Norw
Den_A1 15 11 4 15 6
Den_F1 15 11 4 15 3
Den_F2 15 11 4 15
Swe_A1 15 11 23 22 12 16 46 4 3
Swe_F1 15 11 23 22 12 16 46 4 3
Swe_A2 15 11 23 22 11 16 5 6 4
Swe_F2 15 11 23 22 11 16 5 6 4
Swe_A3 15 11 23 22 16 5 6
Swe_F3 15 11 23 22 16 5 6
Swe_A4 15 10 23 23 4 13 5 3
Swe_F4 15 10 22 23 4 11 4 3
Swe_A5 15 10 23 23 15 22 3 7 4
Swe_F5 15 10 21 23 15 21 2 7 4
Table 4. Description of measured traits.
Trait Unit Description
Survival (0–1) Survival, classified as 0 = dead and 1 = alive
Height cm Total height
Flushing (1–6) Spring phenology based on flushing for the upper half of the living crown registered in 6 classes: 1 = dormant, 2 = buds started to swell, 3 = slightly broken buds where little green can be seen at the top, 4 = broken bud, 5 = developed leaves, 6 = fully developed leaves.
Classification dates: Swe_A1: April 26, 2013 for hybrid aspen and May 7, 2013 for poplar. Swe_A2: May 11, 2013. Swe_A5: May 28, 2013. Swe_F5: May 24, 2013.
Coloration (0–100) Autum phenology classified by coloration of leaves and/or lost leaves in 10% classes where 0 = no autumn colors and/or no leaves lost … 100 = 100% autumn coloration and/or 100% lost leaves.
Classification dates: Swe_A1: Oct 4 and 16, 2013. Swe_A2: Sep 17, 26 and Oct 8, 2013. Swe_A5: 27 Sept, 2013. Swe_F5: Sept 30, 2013.
Table 5. Average survival (%), height (cm), flushing score (1–6) and autumn coloration (%) of hybrid aspen (Hasp) and poplar (Popp) in different trials. The significance probability value associated with species is given by ”Pr > F” for each trait and site.
Trial id Survival, % Height, cm Flushing (1–6) Coloration, %
Hasp Popp All Pr > F Hasp Popp All Pr > F Hasp Popp All Pr > F Hasp Popp All Pr > F
Den_A1 91 89 91 0.6209 277 258 268 0.0391
Den_F1 94 70 86 0.0018 401 166 334 <0.0001
Den_F2 94 89 93 0.1295 289 189 254 <0.0001
Swe_A1 92 69 84 0.0018 351 295 335 0.0178 4.4 3.3 4.0 0.0024 67 49 62 0.0003
Swe_F1 83 11 59 <0.0001 281 100 270 <0.0001
Swe_A2 95 52 85 <0.0001 517 447 508 0.1063 3.9 2.7 3.7 0.0030 59 71 60 0.0045
Swe_F2 82 76 81 0.1611 270 161 244 0.0007
Swe_A3 77 76 77 0.6983 270 260 268 0.0828
Swe_F3 93 83 90 0.0269 236 233 235 0.8777
Swe_A4 50 0 37 0.0255
Swe_F4 69 33 60 0.0690 192 38 152 0.0042
Swe_A5 58 19 38 <0.0001 163 128 145 0.0203 5.3 5.5 5.4 0.1592 46 53 50 0.1428
Swe_F5 82 38 60 <0.0001 258 122 190 <0.0001 5.8 5.7 5.8 0.3380 33 58 45 0.0047
Table 6. Comparison of survival and growth within parallel trials, i.e. between agricultural land (Agri) and forest land (Forest) for sites within similar climatic conditions. Only clones belonging to the groups “Swe_S_Com” are included in the Danish and the southern Swedish sites, while the northern sites include all hybrid aspen clones from the “Swe_N” group and the 16 most northerly poplar clones in “Swe_N”. The statistical significance between each of the two compared sites is given by ”Pr > F”.
Site Hybrid aspen Poplar
Survival, % Height, cm Survival, % Height, cm
Agri Forest Pr > F Agri Forest Pr > F Agri Forest Pr > F Agri Forest Pr > F
Den_A1_F1 91 93 0.4053 265 394 <0.0001 93 70 <0.0001 259 173 <0.0001
Den_A1_F2 91 93 0.5641 265 275 0.3590 93 89 0.3387 259 188 <0.0001
Swe_A1_F1 90 77 0.0005 376 281 <0.0001
Swe_A2_F2 98 81 <0.0001 530 290 <0.0001 47 82 <0.0001 446 178 <0.0001
Swe_A3_F3 79 92 0.0001 282 258 0.0063 70 80 0.0556 264 236 0.0068
Swe_A4_F4 55 76 <0.0001 211 169 <0.0001
Swe_A5_F5 71 85 0.0005 165 244 <0.0001
Table 7a. Average survival of different groups of hybrid aspen and poplar in different trials. The statistical significance of differences between the groups is given by Pr > F.

Table 7b. Average height (cm) of different groups of hybrid aspen and poplar in different trials. The statistical significance of differences between the groups is given by Pr > F.

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Table 8. Summary of means, broad sense heritabilities (H2) and genotypic coefficients of variation (CVG) for survival, height, flushing and coloration per site and species. “N_Obs” = Total number of observations, “N_Clone” = Number of clones, “SE” = Standard error of heritability.
Trial id Hybrid aspen Poplar
N_Obs N_Clone Mean H2 SE CVG N_Obs N_Clone Mean H2 SE CVG
Survival (%)
Den_A1 244 30 91 0.02 0.04 170 21 89 0.08 0.07
Den_F1 254 30 94 0.06 0.04 146 18 70 0.03 0.05
Den_F2 252 30 94 0.04 0.04 163 15 89 0.03 0.05
Swe_A1 706 83 92 0.10 0.03 363 66 69 0.20 0.06
Swe_F1 703 83 83 0.03 0.03 346 31 11 0.03 0.03
Swe_A2 697 82 95 0.21 0.05 220 31 52 0.41 0.08
Swe_F2 698 82 82 0.01 0.02 222 31 76 0.32 0.08
Swe_A3 641 71 77 - - 224 27 76 0.37 0.09
Swe_F3 623 71 93 0.02 0.02 216 27 83 0.25 0.08
Swe_A4 608 71 50 0.08 0.04
Swe_F4 599 70 69 0.06 0.03 108 22 33 0.15 0.10
Swe_A5 552 71 58 0.23 0.05 395 51 19 0.31 0.06
Swe_F5 572 69 82 0.22 0.06 399 50 38 0.16 0.05
Height (cm)
Den_A1 229 30 277 0.23 0.07 12.3 151 21 258 0.14 0.08 8.7
Den_F1 240 30 401 0.26 0.07 11.0 102 18 166 - - -
Den_F2 239 30 289 0.32 0.08 13.7 146 15 189 0.25 0.09 14.1
Swe_A1 647 83 351 0.26 0.05 16.3 250 66 295 0.28 0.06 14.8
Swe_F1 580 83 281 0.23 0.05 16.5 39 28 100 - - -
Swe_A2 653 82 517 0.20 0.04 11.5 110 31 447 0.26 0.11 13.9
Swe_F2 569 82 270 0.38 0.05 17.7 167 31 161 0.23 0.09 16.8
Swe_A3 477 71 270 0.20 0.05 12.9 167 27 260 0.27 0.09 12.4
Swe_F3 579 71 236 0.12 0.04 14.5 179 27 233 0.11 0.06 10.5
Swe_A4 301 71 221 0.23 0.06 16.3
Swe_F4 412 70 192 0.31 0.06 21.8 36 22 38 0.25 0.28 20.0
Swe_A5 322 64 163 0.22 0.07 17.5 74 25 128 0.04 0.21 9.1
Swe_F5 466 63 258 0.28 0.06 17.2 151 37 122 0.00 - -
Flushing (1–6)
Swe_A1 531 83 4.4 0.39 0.05 20.1 232 66 3.3 0.77 0.04 23.8
Swe_A2 631 82 3.9 0.72 0.04 14.9 107 31 2.7 0.35 0.12 11.6
Swe_A5 337 64 5.2 0.19 0.08 14.7 85 29 5.5 0.46 0.12 16.8
Swe_F5 468 63 5.8 0.00 - - 201 41 5.8 0.03 0.06 2.7
Coloration (%)
Swe_A1 611 83 67 0.81 0.03 37.4 235 66 49 0.68 0.05 44.1
Swe_A2 639 82 59 0.71 0.04 36.5 107 31 70 0.75 0.07 29.6
Swe_A5 325 64 46 0.57 0.06 42.0 79 27 53 0.35 0.16 25.5
Swe_F5 468 63 33 0.43 0.06 40.0 177 41 58 0.19 0.09 18.2
Table 9. Genetic correlations (rG) and their standard errors (SE) between height and phenology traits within site. Bold figures are significant at the 5% level.
Trial id Hybrid aspen Poplar
rG SE rG SE
Height × Flushing
Swe_A1 0.58 0.11 0.24 0.17
Swe_A2 0.52 0.11 0.37 0.32
Swe_A5 0.67 0.17
Height × Coloration
Swe_A1 –0.70 0.08 0.05 0.19
Swe_A2 –0.51 0.12 –0.15 0.28
Swe_A5 –0.46 0.18 –0.11 0.75
Swe_F5 –0.46 0.15
Table 10. Genetic site x site correlations (rGE) for survival and height for hybrid aspen and poplar. Bold figures are significant at the 5% level. “SE” = Standard error.
Trial 1 Trial 2 Hybrid aspen Poplar
Survival Height Survival Height
rGE SE rGE SE rGE SE rGE SE
Swe_A1 Swe_F1   0.78 0.09
Swe_A1 Swe_A2 0.47 0.19 0.88 0.08 0.44 0.34 –0.86 0.21
Swe_A1 Swe_F2   0.85 0.07 0.99 0.45 –0.29 0.37
Swe_A1 Swe_F3   0.77 0.13 0.54 0.33 0.41 0.40
Swe_A1 Swe_A3   0.98 0.07 0.69 0.25 –0.54 0.30
Swe_F1 Swe_A2   0.76 0.11
Swe_F1 Swe_F2   0.80 0.08
Swe_F1 Swe_F3   0.64 0.16
Swe_F1 Swe_A3   0.86 0.11
Swe_A2 Swe_F2   0.75 0.10 0.50 0.35 0.17 0.34
Swe_A2 Swe_F3   0.62 0.16 0.84 0.13 0.25 0.39
Swe_A2 Swe_A3   0.86 0.10 0.76 0.14 0.82 0.21
Swe_F2 Swe_F3   0.75 0.13 0.80 0.38 0.61 0.33
Swe_F2 Swe_A3   0.81 0.10 0.84 0.30 0.31 0.29
Swe_F3 Swe_A3   0.67 0.17 0.88 0.12 0.51 0.31
Swe_A4 Swe_F4 0.70 0.24 1.00
Swe_A5 Swe_F5 0.85 0.12 0.78 0.14 0.71 0.16
Swe_A5 Swe_A4 0.56 0.22 0.85 0.14
Swe_A5 Swe_F4   0.90 0.10 0.03 0.40 1.00
Swe_F5 Swe_A4 0.51 0.23 1.00
Swe_F5 Swe_F4 0.30 0.27 0.86 0.12 0.55 0.40

Fig. 2. Relative (%) clonal values (BLUP) for height in relation to the overall trial mean, sorted from the best to the worst clone, within each material group of hybrid aspen at site Swe_A1. Note that the y-axis starts at 60%.