Table 1. Soil characteristics in the five pH treatments of the greenhouse study A. Total C and N (% of dry matter) was for respective treatment, while P, K, Ca, Mg and Al were analysed for plant-available content (mg g–1 dry matter) with the ammonium lactate (AL) method. na = not available.
Limestone
(kg m–3 peat) 		pH level CTot NTot PAL KAL CaAL MgAL AlAL
(distilled H2O) (0.01M CaCl2)
6 5.7 5.1 44.0 0.82 73 251 1524 142 15
4 4.9 4.5 na na na na na na na
3 4.6 4.1 49.4 0.91 74 265 817 138 11
2 4.2 3.7 49.4 0.94 83 287 647 140 11
0 3.4 2.9 50.6 0.96 81 291 66 111 9
Table 2. Information on the forest soils used in study B. Total C and N content (% of dry matter) was given for each site, while P, K, Ca, Mg and Al were analysed for plant-available content (mg kg–1 dry matter) with the ammonium lactate method.
Site pH level CTot NTot PAL KAL CaAL MgAL AlAL
(distilled H2O) (0.01M CaCl2)
Duveholm 5.3 4.6 1.5 0.12 21 70 1138 162 213
Brattön 4.7 3.8 4.3 0.32 26 62 145 44 1368
Dimbo 4.5 3.9 1.6 0.09 11 9 85 11 393
Toftaholm 4.4 4.0 1.5 0.09 22 12 65 6 722
Matteröd 3.9 3.4 4.0 0.17 12 12 52 21 940
Table 3. Site characteristics from where the forest study was established. Annual precipitation (Prec.), annual mean temperature (Temp), and annual vegetation length (Veg.) are averages for the period 1961–1990 from the Swedish Meteorological and Hydrological Institute (SMHI). Soil moisture was given according to the classification used at the Swedish National Forest Inventory.
Variable Site
Brattön Dimbo Duveholm
Coordinates (WGS84) 58°35´N, 11°50´E 59°07´N, 15°43´E 58°58´N, 16°09´E
Elevation (m a.s.l.) 135 90 55
Soil structure Clay-silt moraine Sandy moraine & surged gravel Glacial clay & silty moraine
Soil moisture Mesic-moist Mesic Mesic
Prec. (mm) 900 500 500
Temp. (°C) 6 6 6
Veg. (days) 190 190 180
1

Fig. 1. Height development (cm) for hybrid aspen plants grown in in peat with different pH-levels (A) and in soil collected at five different forest sites (B). Different letters show significant differences among treatments on the measurement occasion (p < 0.05).

Table 4. Dry mass (g) of leaves, stem, roots and total biomass for plants grown in the different peat soil treatments. Values followed by different letters are significantly different column wise at p < 0.05. The p-value for the analyses of each response variable is also shown.
Treatment Leaves Stem Roots Biomass S:R ratio
pH 3.5 9.81 a 13.94 a 12.84 a 36.59 a 1.9 a
pH 4.2 19.27 b 26.10 b 22.76 b 68.12 b 2.1 a
pH 4.6 18.47 bc 28.26 b 24.65 b 71.38 b 1.9 a
pH 5.0 18.10 bc 27.63 b 25.05 b 70.78 b 1.9 a
pH 6.0 14.74 c 20.75 ab 21.25 ab 56.74 b 1.8 a
p-value 0.0001 0.0001 0.0052 0.0001 0.7282
Table 5. Results of the statistical analyses on damage, height and diameter three years after planting.
Effect p-value
Damage Height Diameter
Site 0.1288 0.3002 0.0347
Site prep 0.1561 <0.0001 <0.0001
Site × Site prep 0.0001 <0.0001 0.0004
Clone 0.0008 <0.0001 <0.0001
Site × Clone 0.0633 0.5334 0.3175
Site prep × Clone 0.2321 0.0070 0.0296
Site × Site prep × Clone 0.1623 0.8482 0.8086
Table 6. Percent damaged plants (Dam, %), plant height (Height, cm) and diameter at 50 cm (Diam, mm) three years after planting in the different site preparation methods at each site. Values followed by different letters are significantly different column wise at p < 0.05.
Treatment Brattön Dimbo Duveholm
Dam Height Diam Dam Height Diam Dam Height Diam
No site prep 35 a 147 ab 11.2 a 39 a 160 a 10.6 a 36 a 176 ab 6.9 a
Patch 31 a 144 ab 6.6 b 18 b 113 b 5.5 b 42 a 159 a 3.4 b
Mounding 24 a 174 a 13.6 a 43 a 184 a 11.7 a 40 a 174 ab 7.4 a
Inversion 22 a 136 b 6.5 b 42 a 167 a 10.5 a 51 a 191 b 6.2 a
Table 7. Cause of damage (%) at different sites during the experimental period. Veg. = competing vegetation and Mech. = mechanical damage and leaning stems.
Site Unknown Insects Voles Moose Veg. Climate Mech.
Brattön 31 4 1 0 26 12 26
Dimbo 22 0 1 56 0 1 20
Duveholm 43 17 31 0 0 0 9
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Fig. 2. Height development (cm) for the three clones in the different site preparation treatments. Different letters show significant differences among treatments within the clone after three years (p < 0.05).

3

Fig. 3. Diameter (mm) at planting (at the stem base, black bars) and after three years (at 50 cm, black bars plus grey bars) for each clone in the different site preparation treatments. Different letters show significant differences among soil treatments for respective clone after three years (p < 0.05).