3. Differences in the state of health of stands

Fig. 2.Level of damage to forest stands in 2002, on the basis of assessment of 3-class assessment of defoliation on permanent observation plots

The year 2002 saw a high variability in the level of damage to forest tree species subject to monitoring (Fig. 2). Like in the previous years, fir was the most damaged species. The Tuckey's test confirmed the significance of differences in the defoliation index between tree species in the stands older than 40 years, which indicated a significantly higher level of defoliation in fir stands than in other species (Fig. 6). The defoliation index confirmed the similar share of damaged trees in spruce and oak stands. The share of damaged trees in spruce and oak stands was significantly lower when compared with fir stands, but higher than in other species. The differences in the level of damage to pine and birch stands were insignificant. Beech stands, however, revealed significantly higher healthiness than other species. Similar differences were found in the level of damage to stands based on the share of healthy trees (defoliation 0-10%) and the share of damaged trees (defoliation greater than 25%) - see Tab. 1 i 2, Ryc. 3 i 4.

Fig. 3. The share of trees in different damage classes for the older stands in the period 1998-2002

In the older stands (above 40 years), beech stands exhibited the highest share of healthy trees (19.02%) and birch stands - the high share of healthy trees (12.68%). The lowest share of healthy trees was in oak stands (5.05%) and the slightly elevated share - in spruce stands (6.64%) - see Tab. 1, Ryc. 3. The highest share of damaged trees was recorded in fir stands (58.04%), the high share in oak stands 42.20%) and spruce stands (40.74%) while the lowest share - in beech stands (24.46%) and the low share - in pine (29.43%) and birch (30.65%) stands - see Tab. 1.




Table 1. Percentage shares of trees of different species in different defoliation, discolouration and damage classes - 2002 data for whole country, stands more than 40 years old
Table 2. Percentage shares of trees of different species in different defoliation, discolouration and damage classes - 2002 data for whole country, stands 20 to 40 years old
Fig. 4. The share of trees in different damage classes for the younger stands in 1996, 1998, 2000 and 2002

The younger stands (20-40 years) showed remarkably higher share of healthy trees and lower share of damaged trees than the older stands, irrespective of the dominant species. The share of healthy trees in fir stands was high (90.0%), however, this result based on observations of 20 healthy sample trees only on one plot may not be reliable - see Tab. 2, Ryc. 4. The high share of healthy trees (40.0%) was recorded in younger beech stands. The share of healthy trees in this class reached the lowest value for Scots pine stands (13.74%) and oak stands (16.54%). The share of damaged trees in this age class did not exceed 30%, while it was the highest in oak stands (29.23%) and the lowest in fir stands (5.00%).

Fig. 5. Comparison of variability in the index of defoliation for the older stands in the period 1998-2002 (Tukey Test) - all species together by natural-forest region

The discolouration of tree assimilatory apparatus of all the monitored species was low and did not exceed 2%. The highest percentage share of trees with needle discolouration (2%) was noted in younger spruce stands - see Tab. 1, 2.

The differences in the level of healthiness of older stands indicated the lower level of healthiness of stands in southern Poland than in northern Poland - see Ryc. 2. However, from year to year, these differences are smaller. In 2002, only the Carpathian natural-forest region showed a markedly lower level of healthiness when compared to other regions. The level of healthiness of stands in the Silesian and Sudeten natural-forest regions expressed in the defoliation index showed no significant differences in the healthiness of stands in the Mazowsze-Podlasie, Ma這po-lska and Wielkopolska-Pomerania natural-forest regions. Among the natural-forest regions the significantly higher healthiness of stands were noted in the Baltic natural-forest region. Only Mazury-Podlasie natural-forest region revealed a similar level of healthiness (Fig. 5). The health condition of younger stands was definitely better. Nevertheless, the variability in the defoliation index enabled to distinguish two main groups among the natural-forest regions: southern and northern (Tab. 3).

Plate 4. A Scots pine (Pinus sylvestris L.) tree crown - 35% defoliation - photo by Jerzy Wawrzoniak

The exception was the Carpathian natural-forest region where the healthiness level was considerably higher than other natural-forest regions of southern Poland, but these data were based on a small number of plots.

The level of healthiness for individual species in the natural-forest regions, in majority of cases reflected the differentiation into northern and southern areas.

The older pine stands were found most healthy in the Baltic and Mazury-Podlasie natural-forest regions where the share of healthy trees was higher than 16.00%, and the share of damaged trees did not exceed 21.00%. The highest share of damaged trees was in the Carpathian natural-forest region (60.00%). The younger pine stands exhibited better health state in most of natural-forest regions with the exception of the Mazury-Podlasie natural-forest region where the health condition of older stands was slightly better.

Plate 5. A Norway spruce (Picea excelsa Link.) tree crown - 15% defoliation - photo by Jerzy Wawrzoniak

The variation in the health condition of older spruce stands was higher over larger areas when compared to pine stands. In the Baltic and Wielkopolska-Pomerania natural-forest regions the share of damaged trees did not exceed 30.00%, and the share of healthy trees approximated to 15.00%. In southern Poland, the share of damaged trees exceeded 50.00% in the Ma這polska and Carpathian natural-forest regions and this share in the Sudeten and Silesian natural-forest regions was close to 40.00%. The younger spruce stands were healthier and the differences in health condition between the southern and northern natural-forest regions were not that distinct.

The location of POPs in fir stands is limited to the Ma這polska and Carpathian natural-forest regions. The health condition of these stands was better in the Ma這polska natural-forest region. The younger fir stands were monitored only on one plot in the Carpathian natural-forest region. The healthiness of these stands was high (90.00% of healthy trees).

The broadleaved stands exhibited variable health condition.


Table 3. List of defoliation indexes of the studied species in natural-forest regions, ordered in decreasing sequence according to the column

Plate 6. An pedunculate oak (Quercus robur L.) tree crown - 70% defoliation - photo by Jerzy Wawrzoniak

Among the monitored broadleaved stands, the ones showing the highest level of healthiness were of beech. In a majority of natural-forest regions, the share of damaged trees was less than 20.00% with the exception of the Carpathian natural-forest region (37.28% of damaged trees). More than 30.00% of trees in the Ma這polska, Wielkopolska-Pomerania and Baltic natural-forest regions were classified as healthy. The lowest share of healthy trees was recorded in the Carpathian natural-forest region (4.78%). Exceptionally low number of damaged trees was found in the Sudeten natural-forest region (4.00%). Only a few plots represented the younger beech stands. All plots but one located in the Carpathian natural-forest region exhibited a very high level of healthiness.

Plate 7. A Common birch (Betula verrucosa Ehrh.) tree crown - 25% defoliation - photo by Jerzy Wawrzoniak

The health condition of oak stands is somewhat different. In older stands the number of healthy trees in the Baltic natural-forest region exceeded 10.00%, and the share of damaged trees (2-3 class) was below 30.00%. The healthiness of stands in the Sudeten natural-forest region was at a comparable level. The share of healthy trees in other natural-forest regions did not reach 10.00%, while the share of damaged trees exceeded 40.00%. The level of healthiness was particularly low in the Carpathian natural-forest region where no healthy trees were recorded, and the share of damaged trees was 85.00%. Younger oak stands exhibited lower level of damage than older oak stands in the following natural-forest regions: Mazury-Podlasie, Ma這polska and Wielkopolska-Pomerania. In the Mazury-Podlasie natural-forest region, 35.00% of trees were identified as healthy, and only 15.00% - as damaged. The assessment of health condition in other natural-forest regions was not possible due to the insufficient number of monitoring plots located in the young oak stands.

The health condition of older birch stands was considered good in the Mazury-Podlasie and

Baltic natural-forest regions where 24.44% and 18.42% of trees were healthy, and 20.84% and 21.58% of trees were damaged, respectively. The condition of trees in the Malopolska and Silesian natural-forest regions was significantly worse; the share of damaged trees was greater than 35.00%. In younger birch stands the monitored trees were healthier when compared to trees in the older stands in the majority of the natural-forest regions. The healthiness of the younger stands, like of older stands, was found worse in the Silesian and Ma這polska natural-forest regions.




In 2002, like in the previous years, the most damaged among older coniferous stands were the fir stands, and the least damaged were the pine stands. The oak stands were the most damaged ones within the deciduous stands. The least damaged were the beech stands. The highest level of damage to younger stands was noted in the oak stands while the lowest - in the fir stands.


  Raport 2002