1

Fig. 1. The geographical distribution of moose damage in young stands (development classes 2–4) in the three National Forest inventories (NFIs). The approximate borders of the inventory areas as well inventory years of the 8th and 9th NFI are shown in a) and b). The borders of the former Forest Centers are shown in c). The map was produced from tractwise means of moose damaged plots by kriging (spherical model)in ArcGis. The output cell size was 10 km.

Table 1. Description of the most relevant stand variables and description of the variables used for assessing forest damage at the stand level in the 8th–10th National Forest Inventories (NFI) of Finland 1986–2004. The numbers (8,9,0) after the damage codes refer to the NFIs (10th NFI expressed as 0). For a more detailed description, see Tomppo et al. 2011. View in new window/tab.
Table 2. The occurrence of different standwise damage degree classes of moose damage in forest land in Finland in three National Forest Inventories, split by the main tree species and the development class of the stand. The numbers present the estimated area in km2. View in new window/tab.
2

Fig. 2. The proportion of moose damage in young stands (development classes 2–4) in the area of Forest Centers in Finland. The borders of the Forest Centers are shown in Fig. 1.

3

Fig. 3. The proportion of moose damage in young stands (development classes 2–4) related to stand age in stands dominated by different tree species. The line in produced with Loess-smoothing algorithm in IBM SPSS Statistics.

Table 3. The proportion of moose damage in young stands (development classes 2–4) by main tree species and mixed species in the stand. Data: combined data of NFI8–NFI10 (1986–2008). N = number of plots, s.d. = standard deviation.
Main tree species Mixed species Proportion of moose damage N s.d.
Scots pine None .0497 34795 .217
Norway spruce .1054 10709 .307
Birches .0696 19926 .254
Aspen .1287 171 .336
Alders .0545 110 .228
Rowan .0769 13 .277
Other .0677 1581 .251
Total .0651 67305 .247
Norway spruce None .0059 5726 .077
Scots pine .0838 3698 .277
Birches .0238 7059 .152
Aspen .0645 248 .246
Alders .0071 421 .084
Rowan .0769 13 .277
Other .0198 605 .140
Total .0306 17770 .172
Birches None .0893 3393 .285
Scots pine .0618 3705 .241
Norway spruce .0640 2967 .245
Aspen .1240 242 .330
Alders .0261 230 .160
Rowan .1176 17 .332
Other .0407 491 .198
Total .0706 11045 .256
Aspen None .1429 28 .356
Scots pine .2963 54 .461
Norway spruce .2551 98 .438
Birches .3357 143 .474
Alders .1538 13 .376
Rowan .0000 2 .000
Other .1944 36 .401
Total .2727 374 .446
Alders None .0082 122 .091
Scots pine .0000 55 .000
Norway spruce .0000 107 .000
Birches .0222 180 .148
Aspen .0000 17 .000
Rowan .0000 15 .000
Other .0270 111 .163
Total .0132 607 .114
Rowan None .0000 16 .000
Scots pine .3333 3 .577
Norway spruce .0000 3 .000
Birches .2174 23 .422
Aspen .3333 3 .577
Alders .1667 6 .408
Other .1000 10 .316
Total .1406 64 .350
Other None .0323 62 .178
Scots pine .0909 44 .291
Norway spruce .0625 48 .245
Birches .0441 68 .207
Alders .0000 3 .000
Total .0533 225 .225
All stands None .0469 44142 .212
Scots pine .0741 7559 .262
Norway spruce .0967 13932 .296
Birches .0589 27399 .236
Aspen .1013 681 .302
Alders .0230 783 .150
Rowan .0667 60 .252
Other .0529 2834 .224
Total .0599 97390 .237
4

Fig. 4. The relationships between the proportion of moose damage and the proportion of tree species in young Scots pine dominated stands (development classes 2–4) in the combined data of the 8th–10th National Forest Inventories. The black dots and the solid line show the proportion of Scots pine. The open squares and the dashed line show the proportion of birch species, the open triangles and the dotted line show the proportion of Norway spruce (in Scots pine dominated stands).

Table 4. The occurrence of moose damage in relation to main site type (mineral soil/peatland, proposed thinning operation, accomplished soil preparation or artificial regeneration, according to the GLMM-model and raw data. Data: Stands in development classes 2–4. NFI8–NFI10, all tree species. The moose damage in the model columns were averaged over the levels of class variables, and the continuous variables were fixed in their mean values (for the variables, see Table 6). In the data columns, the p-value is based on the Fishers’s exact test. The odds ratios are also shown. The values in the data columns were computed from the actual plot numbers in a 2 × 2 table.
Variable Value Model Data
Probalility of damage p-value Proportion of damage p-value Odds ratio
Peatland plot No 5.15 <.0001 7.00 <.0001 0.505
Yes 4.09   3.67    
Thinning or clearing proposed No 3.77 <.0001 4.04 <.0001 3.386
Yes 5.58   12.47    
Soil preparation accomblished No 4.17 <.0001 4.69 <.0001 3.273
Yes 5.07   13.87    
Artificial regeration No 4.09 <.0001 4.26 <.0001 2.094
Yes 5.16   8,52    
5

Fig. 5. The proportion of moose damage in raw data (column “Data”) and the predicted probability of damage by the GLMM model (column “Model”), by site types of the stand in mineral soils. Data: development classes 2–4 in the combined data of the 8th–10th National Forest Inventories. The moose damage in the model columns were averaged over the levels of class variables, and the continuous variables were fixed in their mean values (for the variables, see Table 6). The bars marked with the same letter (bar groups treated separately) do not differ in pairwise comparisons (95% confidence level).

Table 5. Classification table (observed vs. predicted number of plots with or without moose damage). Model: generalized mixed linear (GLMM) model, estimated for the presence/absense of moose damage with the glmer function in lme4-package in R. Various measures for the success of the classification are also given. Data: NFI8–NFI10 (1986–2008), development classes 2–4.
  Predicted
No Yes
Observed No 70467 21087
Yes 543 5291
Sensitivity   0.907
Specificity   0.770
Correct classification rate   0.778
False positive   0.230
False negative   0.093
Positive predictive value   0.200
Negative predictive value   0.992
Area under the curve (AUC)   0.920
Table 6. Results of the generalized mixed linear model (GLMM), estimated for the presence/absense of moose damage with the glmer function in lme4-package in R. The fixed effects of the explanatory variables are shown. Data: NFI8– NFI10 (1986–2008), development classes 2–4, total N = 93390.
Variable Estimate Std. Error z-value p-value
(Intercept) –3.213e+00 1.979e–01 –15.020 < 0.001
Stand mean age (years) –1.832e–02 1.950e–03 –9.394 < 0.001
Site type 2 1) 5.017e–01 1.417e–01 3.539 < 0.001
Site type 3 1) 7.831e–01 1.419e–01 5.519 < 0.001
Site type 4 1) 7.960e–01 1.462e–01 5.443 < 0.001
Site type 5 1) 8.556e–01 1.591e–01 5.378 < 0.001
Site type 6 1) 1.108e+00 2.051e–01 5.401 < 0.001
Elevation of the plot (m) 3.927e–04 2.954e–05 13.297 < 0.001
Stand basal area (m2/ha) –9.158e–02 3.711e–03 –24.680 < 0.001
Peatland (0/1) –2.411e–01 6.045e–02 –3.988 < 0.001
Thinning proposed (0/1) 4.099e–01 3.620e–02 11.322 < 0.001
Artificial regeneration (0/1) 2.427e–01 3.970e–02 6.114 < 0.001
Soil preparation accompished (0/1) 2.053e–01 4.066e–02 5.048 < 0.001
Main tree species Norway spruce 2) –1.224e+00 6.059e–02 –20.203 < 0.001
Main tree species birches 2) 1.597e–01 6.364e–02 2.510 0.012
Main tree species aspen 2) 2.848e+00 1.530e–01 18.613 < 0.001
Main tree species alder 2) –8.108e–01 3.808e–01 –2.129 0.033
Main tree species rowan 2) 3.891e–01 4.163e–01 0.935 0.349
Main tree species other 2) –8.537e–01 3.290e–01 –2.594 0.009
Mixed tree species Scots pine 3) 3.881e–01 7.951e–02 4.881 < 0.001
Mixed tree species Norway spruce 3) 4.332e–01 4.615e–02 9.387 < 0.001
Mixed tree species birches 3) 2.648e–01 3.981e–02 6.651 < 0.001
Mixed tree species aspen 3) 1.724e+00 1.533e–01 11.244 < 0.001
Mixed tree species alder 3) –9.798e–02 2.624e–01 –0.373 0.708
Mixed tree species rowan 3) –4.107e–01 5.885e–01 –0.698 0.485
Mixed tree species other 3) 1.345e–01 1.034e–01 1.301 0.193
1) Compared with the most fertile site type 1
2) Compared with s stands with Scots pine as the main tree species
3) Compared with s stands without any mixed species