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Fig. 1. Location of the study area and the arrangement and characteristics of sample plots.

Table 1. Measurements taken on sample plots in 2003 and 2007.
Measured characteristic Rules for measurement and evaluation of characteristics
Measurements on an area of 1038 ha in 2003, on 221 sample plots
Picea seedlings (two size classes, current-year
seedlings were not included):
1. small: height < 26 cm
2. large: 26 cm ≤ height < 50 cm 		Seedling height was measured and two types of microsites were distinguished:
1. forest floor (bare ground, ground with vegetation, litter and also the exposed mineral soil formed by tree fall) and mounds (formed by the root plates of uprooted trees)
2. decaying wood (stumps and fallen deadwood)
Picea saplings (eight classes):
1. 0.5 m ≤ height < 1.3 m
2. DBH1 < 1 cm
3. 1 ≤ DBH< 2 cm
4. 2 ≤ DBH< 3 cm
5. 3 ≤ DBH< 4 cm
 Sapling height or DBH were measured and four types of microsites were distinguished:
1. forest floor
2. mounds
3. stumps
4. fallen deadwood
6. 4 ≤ DBH< 5 cm
7. 5 ≤ DBH< 6 cm
8. 6 ≤ DBH< 7 cm		 For last three classes of saplings, microsite categories were not given because identification was often uncertain.
Measurements on an area of 45 ha w 2007, on 20 sample plots
Deadwood type  
Standing entire dead trees with DBH ≥ 7 cm DBH and height of trees
Snags – standing snapped trees with stump height
≥ 1.3 m and DBH ≥ 7 cm) 		Height and two diameters: under the ground and at the top of snag
Stumps with height < 1.3 m and diameter above
the ground ≥ 10 cm 		Height and two diameters: under the ground and at the top of stump
Fallen deadwood:
• uprooted trees (windthrown trees with exposed root plates )
• fallen logs, trunks or branch fragments (pieces of a trunk or large branches etc.)
Deadwood thinner than 7 cm in diameter was not taken into account. 		Fallen deadwood was subdivided into smaller size categories during measurement, each category having a span of 8 cm in diameter: 7–14.9, 15–22.9, 23–30.9, etc. At the end of each deadwood piece, the width and height of the cross-sectional area were measured. The length of the piece and stage of decomposition were recorded on an 8 level scale (Table 2).
Regeneration growing on deadwood:  
Picea seedlings (two size classes, current-year seedlings were not included):
1. small: height < 26 cm
2. large: 26 cm ≤ height < 50 cm 		Height of seedling and the type of microsite it grew on (stump or fallen deadwood). The size category of fallen deadwood and coarse woody debris decomposition were recorded.
Saplings on woody microsites were not taken into account because they occurred infrequently and in numbers too low to enable statistical analysis.
Other characteristics measured on sample plots  
Living trees – all trees with DBH ≥ 7 cm (all species were included) DBH and height of trees.
Tree losses – all trees that died over 15 years before
the 2007 measurement 		It was recorded which trees died relative to the 1992 measurement (tree coordinates and DBH were known from 1992).
Saplings – all individuals with height ≥ 0.5 m but with
DBH < 7 cm (all species were included) 		Number of saplings on the sample plot.
Slope of sample plot [°] Slope of the land on which the sample plot was located.
Canopy closure [%] Defined as the percentage of ground area shaded by overhead foliage and estimated visually.
1DBH - diameter at breast height
Table 2. Characteristics of different decay stages of coarse woody debris (Holeksa 1998, modified).
Decay stage Surface Shape Depth of penetration of sharpened tool Branches
I Smooth Round Hard, fresh wood All branches present, elevated above ground
II Smooth Round Max. 1 cm or wood bends under the pressure of tool Branches over 2 cm thick present
III Crevices up to 0.5 cm deep Round Up to 2 cm Branches over 3 cm thick present
IV Crevices about 0.5 cm deep Round Up to 4 cm Only base parts present
V Crevices about 1 cm deep Round Up to 6 cm Only thickest base parts present
VI Several cm thick pieces torn off Slightly flattened Wood solid only in the central part of log Only thickest base parts present
VII Covered with furrows several cm deep Distinctly flattened Tool goes through Lack of any remains
VIII Often covered with vegetation Flattened, covered with vegetation Tool goes through Lack of any remains
Table 3. Characteristics of stands and coarse woody debris as measured on twenty 0.05 ha sample plots in 2007.
Variables Mean Min–Max Standard deviation
Volume of living trees [m3 ha-1] 375 131–724 170
Density of living trees [trees ha-1] 520 80–1205 287
Basal area of living trees [m2 ha-1] 37.9 16.4–63.2 13.4
Sapling density [individuals ha-1] 700 0–2600 741
Total volume of coarse woody debris [m3 ha-1] 180 45–422 104
Volume of fallen deadwood and stumps [m3 ha-1] 65 12–172 48
Height of stumps [m] 0.55 0.15–1.20 0.25
Canopy closure [%] 41.2 10–85 22.7
Tree losses [m3 ha-1 year-1] (over the past 15 years) 7.0 0.0–20.0 5.7
Slope of sample plot [degrees] 17.8 0–30 8.0
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Fig. 2. Density of Picea seedling and saplings (with a diameter at breast height of less than 4 cm) on different microsites.
Note: Values with different letters differ significantly at p < 0.05 as evaluated using the Tukey post-hoc test. Two
separate analyses were conducted for seedlings and saplings.

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Fig. 3. Density and shares of the various size classes of Picea seedlings and saplings with a DBH (diameter at breast height) of less than 4 cm on different microsites.

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Fig. 4. Total area of stumps and fallen deadwood in the various decay stages (top chart) and areas of those microsites depending on size class and decay stage (bottom chart). Results of the Tukey test are given next to the size classes of fallen deadwood in the chart legend.

Table 4. Spearman correlation matrix of independent variables (characteristics of 20 sample plots).
  Basal area of living trees Density of living trees Volume of living trees Tree losses over 15 years Canopy closure Sapling density (all species) Slope of sample plot Volume of fallen deadwood and stumps Total volume of coarse woody debris
Basal area of living trees 1.000                
Density of living trees 0.245 1.000              
Volume of living trees 0.932*** 0.084 1.000            
Tree losses over 15 years -0.414 -0.545* -0.313 1.000          
Canopy closure 0.430 0.724*** 0.288 -0.612** 1.000        
Sapling density (all species) -0.242 -0.378 -0.165 0.096 -0.169 1.000      
Slope of sample plot 0.242 -0.141 0.225 0.006 -0.100 0.541* 1.000    
Volume of fallen deadwood and stumps -0.206 -0.673** -0.134 0.597** -0.716*** 0.265 0.260 1.000  
Total volume of coarse woody debris -0.223 -0.658** -0.104 0.765*** -0.650** 0.224 0.238 0.853*** 1.000
Significance: *p < 0.05; **p < 0.01, ***p < 0.001.
Table 5. Density of seedlings on woody microsites in different decay stages, according to diameter of fallen deadwood and stumps (wood in decay stages I–II was not taken into account).
  Number of coarse woody debris pieces Height of Picea
seedlings < 26 cm 		26 cm ≤ height of Picea
seedlings < 50 cm
Mean Median Top quartile Max Mean Median Top quartile Max
individuals / m2
Decay stage of stumps and fallen deadwood III (a) 137 0.06 0.0 0.0 7.6 0.00 0.0 0.0 0.0
IV (ab) 162 0.48 0.0 0.0 24.9 0.00 0.0 0.0 0.0
V (ab) 162 1.23 0.0 0.0 35.3 0.28 0.0 0.0 35.3
VI (bc) 189 1.90 0.0 0.0 52.6 0.27 0.0 0.0 20.8
VII (bc) 144 2.09 0.0 0.0 46.8 0.04 0.0 0.0 5.4
VIII (c) 98 3.77 0.0 0.0 65.1 0.22 0.0 0.0 10.0
Size class of fallen deadwood 7–14.9 cm (a) 449 0.22 0.0 0.0 15.8 0.00 0.0 0.0 0.0
15–22.9 cm (b) 150 0.95 0.0 0.0 49.7 0.03 0.0 0.0 4.7
23–30.9 cm (c) 59 2.71 0.0 1.9 36.0 0.28 0.0 0.0 10.0
≥ 31 cm (c) 41 3.51 0.0 4.7 22.2 0.29 0.0 0.0 5.4
Diameter of stumps 10–14.9 cm (a) 51 0.00 0.0 0.0 0.0 0.00 0.0 0.0 0.0
15–22.9 cm (a) 50 2.81 0.0 0.0 52.6 0.71 0.0 0.0 35.3
23–30.9 cm (a) 33 3.56 0.0 0.0 32.5 0.00 0.0 0.0 0.0
≥ 31 cm (b) 59 8.69 0.0 9.3 65.1 0.92 0.0 0.0 20.8
Note: Values designated with different letters differ significantly at p < 0.05 as evaluated by the nonparametric Kruskal–Wallis test corrected with a post hoc test for the number of comparisons. Analyses were conducted for total number of seedlings (small and large).
Table 6. Results of logistic regression analysis of the probability of Picea seedling occurrence on fallen deadwood on sample plots.
Independent variable Evaluation (standard error) Wald
chi-square 		Odds ratio (95% confidence interval) p
Decay stage [1–8] 0.705 (0.082) 73.7 2.02 (1.72-2.38) 0.001
Diameter of deadwood [cm] 0.085 (0.016) 27.3 1.09 (1.05-1.12) 0.001
Volume of living trees [m3 0.05 ha-1] 0.047 (0.018) 6.9 1.05 (1.01-1.09) 0.01
Number of living trees [trees 0.05 ha-1] -0.105 (0.018) 33.8 0.90 (0.87-0.93) 0.001
Sapling density [trees 0.05 ha-1] -0.012 (0.006) 3.9 0.99 (0.98-1.00) 0.05
Land slope [°] -0.063 (0.028) 4.9 0.94 (0.89-0.99) 0.05
Constant -4.327 (0.779) 30.9   0.001
Quality characteristics of the model: Likelihood-ratio test: χ2 = 217; p < 0.0001.
Coefficients: McFadden’s R2 – 0.409, Nagelkerke R2 – 0.344, Cragg-Uhler (Nagelkerke) R2 – 0.477.
The model correctly predicted results in 95% of the cases. Tolerance values for explanatory variables exceeded 0.25. The mean value for standardized Pearson’s residuals was -0.005, standard deviation: 0.884; more than 95% of results were within 2 standard deviations.
Table 7. Results of logistic regression analysis of the probability of Picea seedling occurrence on stumps on sample plots.
Independent variable Evaluation (standard error) Wald
chi-square 		Odds ratio (95% confidence interval) p
Diameter of stump [cm] 0.128 (0.024) 27.9 1.14 (1.08–1.19) 0.001
Height of stump [cm] -0.066 (0.019) 12.1 0.94 (0.90–0.97) 0.001
Sapling density [individuals 0.05 ha-1] 0.026 (0.009) 8.1 1.03 (1.00–1.04) 0.01
Constant -3.066 (0.988) 9.6   0.01
Quality characteristics of the model: Likelihood-ratio test: χ2 = 73; p < 0.0001.
Coefficients: McFadden’s R2 – 0.399, Nagelkerke R2 – 0.291, Cragg-Uhler (Nagelkerke) R2 – 0.514.
The model correctly predicted the results in 88% of the cases. Tolerance values for explanatory variables exceeded 0.25. The mean value of standardized Pearson’s residuals was -0.033, standard deviation: 0.889; 95% of the results were within 2 standard deviations.