Table 3 (A) Growth, phenology, branchiness, leaf, and wood traits for poplar and black locust measured in 2010 at the end of the first SRC rotation or at the end of the second year in the SRF (n = 20 individuals per planting density and per species). When data are available for SRC only, i.e., for wood traits, differences between species are indicated: **P ≤ 0.01, ***P ≤ 0.001. (B) Leaf traits for poplar and black locust measured in 2012 at the end of the second SRC rotation or the end of the fourth year in the SRF (n = 20 individuals per planting density and per species). The differences between species, planting density, and their interaction are presented in Table 4

dHt/d t (cm day⁻¹)

0.61 ± 0.08

0.64 ± 0.06

0.73 ± 0.08

0.76 ± 0.07

dnl/d t (day⁻¹)

0.13 ± 0.01

0.17 ± 0.01

0.16 ± 0.01

0.20 ± 0.01

Bud burst (day of year)

94.8 ± 1.8

96 ± 0.0

94.1 ± 1.6

96.0 ± 0.0

Bud set (day of year)

263.3 ± 2.8

271 ± 0.0

265.7 ± 3.6

273.8 ± 1.9

GSL (days)

168.8 ± 3.4

175 ± 0.0

171.8 ± 5.1

177.8 ± 1.9

LA (cm²)

128.0 ± 9.7

52.9 ± 3.8

122.6 ± 8.0

69.2 ± 7.4

SLA (cm² g⁻¹)

136.7 ± 8.0

84.7 ± 2.8

147.2 ± 4.2

75.6 ± 2.0

N_leaf (mg g⁻¹)

41.2 ± 1.1

11.3 ± 0.8

39.9 ± 1.7

15.9 ± 1.3

C/N

11.9 ± 0.3

41.0 ± 2.1

12.3 ± 0.5

31.5 ± 2.8

Δ¹³C leaf (‰)

16.7 ± 0.3

20.4 ± 0.1

17.2 ± 0.3

20.4 ± 0.2

N_stem (mg g⁻¹)

9.6 ± 0.4 ***

5.0 ± 0.5

-

-

C/N

49.4 ± 2.2 ***

99.1 ± 8.6

-

-

N_removal (kg N ha⁻¹ year⁻¹)

15.9 ± 2.6 ***

4.7 ± 0.7

-

-

Δ¹³C wood (‰)

17.2 ± 0.2 **

19.3 ± 0.1

-

-

Sylleptic number

8.7 ± 1.3

6.1 ± 1.7

10.9 ± 1.1

2.0 ± 0.9

LA (cm²)

180.7 ± 24.6

146.1 ± 9.4

177.0 ± 16.0

131.6 ± 16.7

SLA (cm² g⁻¹)

130.4 ± 7.2

132.4 ± 3.1

127.7 ± 6.4

109.8 ± 1.9

N_leaf (mg g⁻¹)

37.9 ± 0.2

32.9 ± 0.2

43.2 ± 0.4

24.9 ± 0.2

C/N

12.2 ± 0.8

13.7 ± 0.8

11.1 ± 1.0

18.3 ± 1.1

Δ¹³C leaf (‰)

17.4 ± 0.6

18.6 ± 0.8

18.2 ± 0.6

19.8 ± 0.2