3. Differences in the state of health of stands in 2003

Jerzy Wawrzoniak, Jadwiga Małachowska

Biotic and abiotic agents including anthropogenic sources whose intensity vary in time and space affect forest ecosystems. In effect, the level of damage to stands is changing depending on the configuration of environmental factors specific for a given year. This differentiated level of damage to forest stands is influenced by different geological ad soil conditions, as well as species composition of stands. This leads to the areal heterogeneity level of damage to stands.

The year 2003 saw similar level of damage both to coniferous and broadleaved stands. Coniferous stands exhibited slightly lower share of trees without defoliation - 7.97% than broadleaved stands - 9.08% (Table 1).

However the share of trees with defoliation above 25% in broadleaved stands was higher - 38.92% when compared to coniferous stands - 32.69%. Among broadleaved species oak stands featured the highest level of damage. Only 2.02% of oaks were found healthy (defoliation below 10%), while 50.04% of trees were damaged (defoliation above 25%). The share of healthy trees in beech stands was high - 17.84% (defoliation below 10%). The share of damaged trees in these stands was markedly higher - 27.85%. The share of healthy trees in birch stands, which generally exhibit level of damage comparable to beech stands, was in 2003 distinctly lower - 7.64% while the share of damaged trees was high - 397.99% (Table 1).

Among the monitored coniferous stands, the ones showing high level of damage were spruce and fir. The share of healthy trees in spruce stands (defoliation below 10%) was merely 5. 92% while of damaged trees (defoliation above 25%) - 41.97%. Slightly elevated was the share of healthy trees in fir stands - 6.52% and considerable higher share of damaged trees - 62.07%. The share of healthy trees in pine stands was higher - 8.12% while the share of damaged trees was lower amounting to 29.74%, which proves higher level of healthiness of this species (Table 1).

In 2003, the discolouration of tree assimilatory apparatus of monitored coniferous and broadleaved species was low. Thus, the level of damage to stands being a combination of defoliation and discolouration can be assumed equal the defoliation level.

The defoliation index is also used as a measure of the level of damage to stands. The highest values of his index are found for fir - 3.51 and oak - 3.20 stands, the lower - for beech - 2.51, birch - 2.93, spruce 3.01 and pine - 2.76. The defoliation indices for particular species in the stands in 2003 indicated in a majority of cases statistically significant differences.

The level of damage to stands in the natural-forest regions expressed by the defoliation index oscillates between 2.52 and 3.33. The lower values of the defoliation index were noted in the Baltic and Wielkopolska-Pomerania natural-forest regions. The highest value of the index was found in fir - 3.63 and pine - 3.61 stands, and in the e case of broadleaved species - for oak - 4.28 and beech 2.94 stands. The highest value of the defoliation index for birch stands - 3.27 was noted in the Małopolska natural-forest region (Table 2). The lower index value was found for pine - 2.52, beech - 2.05 and birch - 2.68 in the Baltic natural-forest region and for spruce - 2.30 in Wielkopolska-Pomerania natural-forest region. The defoliation index value for oak stands was the lowest in the Sudeten natural-forest region - 2.80 (Table 2). Statistically significant differences in the defoliation index were found between the Baltic natural-forest regions where the index value was the lowest when compared with all other regions. Also the Carpathian natural-forest region with the highest index value statistically differs from other regions.

   *)   weight average calculated acc. to the formula: x=(n1+2n2+...+10n10):N. where: n - number of trees in 10% ranges of defoliation. N - number of all trees. 1. 2. .... 10 - number of ranges

The share of healthy trees (class 0) and the share of damaged trees (classes 2 and 3) in the monitored stands were compared. The share of healthy trees in the stands of the Baltic natural-forest region was 17.55% and only 24.90% of damaged trees. The share of healthy trees was slightly lower, yet above 10% was found in the Mazury-Podlasie natural-forest region. Slightly lower share of such trees was noted in the Silesian natural-forest region - 3.21%, Carpathian - 3.31% and Małopolska - 3.54% regions. The share of damaged trees in these regions was markedly higher and ranged between 35.93% and 56.90%, while in the regions of northern and north-eastern Poland from 24.90% in the Baltic to 29.02% in the Wielkopolska-Pomerania natural-forest regions.

Pine stands with the highest share of healthy trees and the lowest share of damaged trees classified as the healthiest were located in the Baltic - 16.51% and Mazowsze-Podlasie - 13.05% natural-forest regions. The highest shares of damaged trees, above 35.00% were found in the Carpathian, Małopolska and Mazowsze-Podlasie natural-forest regions. The share if healthy trees in those stands did not exceed 5.00%.

The health condition of spruce stands in the Baltic natural-forest region was considered good; the share of healthy trees approximated to 20.0%, while the share of damaged trees in those stands was relatively low - 35.00%. The healthiness of spruce stands in the Carpathian and Małopolska natural-forest regions was markedly worse. The share of healthy trees was below 2.00%, and of damaged trees exceeded 50.0%.

The POPs with fir stands were located only in the Małopolska and Carpathian natural-forest regions. The share of healthy trees in those stands in the Małopolska natural-forest region was considerably higher - 9.50% than in the Carpathian natural-forest region - 5.69%. However the share of damaged trees in the both natural-forest regions was very high - 45.00%.

The health condition of beech stands was high. The share of health trees (class 0) ranged between 25.00% in the Małopolska and 42.50% in the Wielkopolska-Pomerania natural-forest regions. The exception were beech stands in the Carpathian and Silesian natural-forest regions where the share of health trees was respectively: 3.15% and 8.33%. The share of damaged trees (class 2 and 3) in beech stands was from12.79% in the Baltic natural-forest region to 41.30% in the Carpathian natural-forest region.

The healthiness of oak stands was significantly worse when compared to beech stands. Apart from the Carpathian and Silesian natural-forest regions, where the number of permanent observation plots was very innumerate (2 and 3, respectively) the share of healthy trees in the remaining natural-forest regions oscillated from 0.26% in the Silesian to 7.14% in the Mazury-Podlasie natural-forest regions. The share of damaged trees was the highest - 61.43% in the Mazury-Podlasie natural-forest region while the lowest - 35.45% in the Silesian natural-forest region.

The health condition of birch stands was superior when compared to oak stands. The share of trees in those stands ranged from 2.14% in the Silesian natural-forest region to 13.50% in the Baltic natural-forest region. The highest share of damaged trees - 47.73% was found in the Małopolska natural-forest region, while the lowest - 29.47% in the Mazury-Podlasie natural-forest region.