8. Assessment of natural regeneration in 2003 and changes in the years 1998-2003 -

Jerzy Wawrzoniak, Jadwiga Małachowska

In 2003, after five years, reassessment of natural regeneration was performed on 148 second-level POPs, including its vitality and age. The analysis of changes that occurred within natural regeneration categories was carried out with regard to the dominant species in a stand and with regard to forest habitat types.

Table 13. Number of species by natural regeneration categories on the second-level POPs in the years 1998, 1999 and 2003 - the mean for the dominant species in a stand and forest habitat type.

Taking into consideration the number of species in young natural regeneration registered on POPs in 2003 and in 1989-1999, a trend of growth in the number of registered species could be observed over the last five years - Table 13. In pine stands growing in fresh mixed coniferous forest and fresh coniferous forest habitats (these habitats were represented by the largest number of plots) an increase in the number of species by 0.47 and 0.42 on average was observed. The highest growth in the number of species (by 3.5) was reported in pine stands in the upland forest habitat (represented by only 2 plots). In spruce, beech and oak stands, the trend of growth in the number of species was lower.

Quantitative changes in individual species registered in young natural regeneration pointed to the dominant growth trend. Of 23 registered species, the quantitative increase of 12 species was observed in the past five years. The decline concerned 8 species, while the quantity of 3 species did not change - Table 14.

Table 14. Average quantity, age and vitality of young natural regeneration on the second-level POPs*) - specification for the country - a comparison by years (on two POPs young natural regeneration was not found)

The analysis of six main forest tree species in the monitored stands, indicates a quantitative increase of birch, pine and spruce seedlings and a decrease in the abundance of beech, oak and fir seedlings. The average age of young natural regeneration of the majority of discussed species increased, only the age of pine seedling largely lowered. Similar tendency was found for vitality. Seedling vitality of all monitored species, except for pine showed a rising tendency (Table 14).

In the younger underwood category, a total number of 21 species was registered, of which 12 increased their abundance and 9 showed decreased abundance in comparison with the figures from 5 years back. Among the six main species whose stands are subject to monitoring, spruce and beech significantly increased their population, while birch and pine did it to a lesser degree. The abundance of the younger underwood of pine and oak decreased. The average vitality of all the main species showed a trend towards improvement, except for beech. The average age of this natural regeneration category increased for all the six species - Table 15.

Table 15. Average quantity, age and vitality of younger underwood on the second-level POPs*) - specification for the country - a comparison by years (on 28 POPs younger underwood was not found)

While studying the occurrence of younger underwood with relation to the dominant species in a stand, it should be stated that the highest number of species was registered in pine stands. 19 species were found there, of which 12 showed an increase in abundance, and 7 - a decline. In spruce stands, 16 species were present; an increase in abundance was reported with regard to 10 species, while 6 species showed its decline. The same number of species was registered in the younger underwood of oak stands. In these stands, 10 species showed an increase in abundance, 5 species - a decline and the abundance of one species did not change. Beech stands featured the occurrence of 11 species in younger underwood, and only one species showed a decline in abundance.

20 species of older underwood were registered. 13 species showed increase in abundance, while 7 species - a decreased. Among the main species, the abundance of the older underwood of oak, fir and pine increased, while abundance of birch, beech and spruce declined. Vitality level improved in 16 species and deteriorated in 4 species. Among the main species, the older pine saplings showed average vitality deterioration, while vitality of the older saplings of oak remained at the same level. Spruce, fir and beech improved their vitality level. The average age of older underwood increased for 18 species and decreased for 2 species. All the main tree species showed an increase in mean age - Table 16.

The number of species of older underwood, with regard to the dominant species on POPs, was as follows: pine stand - 12 species, oak stands - 14 species, spruce stands - 12 species and beech stands - 6 species.

Table 16. Average quantity, age and vitality of older underwood on the second-level POPs*) - specification for the country - a comparison by years (on 45 POPs, older underwood was not found)

As far as the abundance of older underwood of the main tree species is concerned, it has to be noted that, depending on the dominant species, the quantities of oak and pine increased while of fir, birch, beech and spruce decreased. In spruce stands there was an increase in the number of older underwood for all monitored species. Fir and spruce showed the largest increase in the number of trees. In beech stands, only older underwood of beech and fir was found among the main tree species. Over the five-year period, the abundance of beech increased while of fir remained on the same level.

In oak stands, older underwood of pine was not found, and the marked decrease in oak abundance was noted. The abundances of older beech, birch and fir underwood increased.

A rising tendency in the number of naturally regenerated species was found over the last five years. An increase in mean abundance for the majority of species in all natural regeneration categories was also recorded. Average vitality and average age of the natural regeneration of six main forest tree species showed a rising tendency.