Table 1. Soil characteristics in 18-year-old silver birch stand in upper 0–10 cm soil layer. Average ± standard error is presented.
Soil characteristics  
N, % 0.110 ± 0.002
P, mg kg–1 78.3 ± 2.3
K, mg kg–1 280.3 ± 3.6
Ca, mg kg–1 504.0 ± 21.7
Mg, mg kg–1 79.5 ± 7.1
C, % 1.42 ± 0.07
pH 5.69 ± 0.03
Bulk density, g cm–3 1.34 ± 0.02
Texture Loamy sand
Table 2. Parameter estimates of the regression Eq. 1 for estimation of the aboveground biomass.
  N a b R2
2004 1) 11 142.19 2.25 0.99
2005 10 125.17 2.30 0.99
2006 12 114.13 2.39 0.99
2007 10 123.18 2.38 0.99
2008 10 88.494 2.55 0.98
2009 2) 10 136.03 2.33 0.99
2013 3) 7 82.09 2.60 0.98
1) Data from Uri et al. 2007a
2) Data from Uri et al. 2012
3) Leafless biomass
R2 = coefficient of determination
Table 3. Stand characteristics and biomass and production dynamics of naturally afforested silver birch stand growing on abandoned agricultural land. H – average height of the stand, D1.3 – average breast height diameter of the stand; N – stand density, G – basal area of the stand, CAI – current annual increment of stemwood, MAI – mean annual increment of stemwood.
Stand age H D1.3 N trees G Leaves Branches Twigs Stemwood Stembark CAI MAI
yr m cm ha–1 m2 ha–1 Mg ha–1 Mg ha–1 yr–1
8 6.6 ± 0.6 3.2 ± 0.1 11 633 11.3 3.5 3.0 0.6 20.4 3.7 7.4 3.0
9 7.6 ± 0.5 3.8 ± 0.1 11 533 13.2 2.9 3.7 1.0 24.4 4.4 4.7 3.2
10 8.5 ± 0.6 4.4 ± 0.1 10 200 15.2 2.8 3.9 0.7 30.8 5.0 7.0 3.6
11 9.3 ± 0.7 4.7 ± 0.1 9500 16.6 2.1 4.4 0.8 38.4 5.6 8.2 4.0
12 10.4 ± 0.7 5.4 ± 0.2 8300 18.7 3.7 5.0 1.5 44.6 6.8 7.4 4.3
13 1) 10.9 ± 0.8 5.8 ± 0.2 7670 20.1 3.1 5.0 0.8 51.6 7.2 7.4 4.5
14 12.2 ± 0.6 6.4 ± 0.2 6567 21.3 n.e. 6.0 0.8 56.6 8.3 5.7 4.6
15 13.2 ± 0.6 7.9 ± 0.3 4233 20.7 n.e. 6.3 1.0 65.6 8.5 9.7 4.9
16 14.4 ± 0.5 9.1 ± 0.3 3133 20.5 n.e. 6.9 0.8 72.2 8.7 6.8 5.1
17 16.0 ± 0.6 9.9 ± 0.3 2733 20.9 n.e. 7.3 0.8 76.3 9.1 4.6 5.0
n.e. - not estimated
1) - Data from Uri et al. 2012
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Fig. 1. The dynamics of current annual increment (CAI) and mean annual increment (MAI) in relation to self-thinning of the silver birch stand growing on abandoned agricultural land. Self-thinning is expressed as a share of number of dead trees out of previous years’ total number of trees.

Table 4. Nitrogen budget and storages of 10-year-old silver birch stand growing on abandoned agricultural land.
  Production, Mg ha–1 Biomass,
Mg ha–1 		N,
% 		N storage,
kg ha-1 		N demand,
kg ha–1 yr–1
Trees Aboveground part
Leaves 2.81 2.81 2.507 70.45 70.45
Stemwood 6.45 30.82 0.178 54.86 11.48
Stembark 0.56 4.99 0.532 26.55 2.98
Twigs 0.72 0.72 0.827 5.95 5.95
Branches 0.16 3.85 0.497 19.13 0.80
Aboveground total 10.70   91.66
  Belowground part
Stump 0.61 3.59 0.230 8.25 1.41
Coarse roots 0.82 4.77 0.473–0.622 25.99 4.45
Fine roots 0.89 1.35 0.655 8.98 5.83
Belowground total 2.32   11.69
Trees, total 13.02   103.35
Herbs Aboveground part 0.12 0.12 1.746 2.05 2.05
Belowground part 1.68 1.68 0.768 12.90 12.90
1. Total N demand for plants   118.3
Leaching           0.92
Gaseous losses
N2O-N           0.12
N2-N           83.0
2. Total output fluxes   84.04
Deposition           6.4
Herbs starting pool           9.8
Transformations
Net nitrogen mineralization           156.0
N retranslocation in trees           45.0
3. Total input fluxes   217.2
Total 3 – (1+2)   14.8
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Fig. 2. Seasonal dynamics of carbon dioxide (A), methane (B), nitrous oxide (C), dinitrogen (D) emissions and N2:N2O ratio (E) in the Kambja birch stand, Estonia in 2006. Median, 25 and 75%, and min-max values are shown. Numbers show median values.

3

Fig. 3. Leaf abscission dynamics in young silver birch stand growing on former agricultural land.

4

Fig. 4. The dynamics of nitrogen concentration in different fractions of the 10-year-old silver birch stand growing on former arable land.