DIGITALNA ARHIVA ŠUMARSKOG LISTA
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| ŠUMARSKI LIST 11-12/2002 str. 41 <-- 41 --> PDF |
I. Anić. M. Oršanić, M. Dctclić: REVITALIZACIJA DEGRADIRANOGA EKOSUSTAVA NAKON SUŠENJA ... ed with alders and other pioneer species. The newly-established stands were restocked and tended when needed. These stands have currently reached the stage of the young growth. The stand canopies are closed and vital and contain sufficient number of plants per area unit. The results confirm past perceptions concerning the choice of tree species to rehabilitate degraded sites in Posavina. Narrow-leaved ash proved to be the most suitable species. In terms of participation, heights and vitality, it dominates other species in the stands. It has achieved heights between 5.18 and 10.19 m, and breast diameters between 4.29 and 8.12 cm. The average height increment in the past period ranged from 0.43 (min) to 0.72m (max.). No significant differences in the height increment were found in the plots. For the moment, pedunculate oak does not play an important role in the stand structure. It occurs under the crowns of narrow-leaved ash in the developmental stages of seedlings and saplings. Attempts to favour oak with the practice of restocking have proved unproductive (plots 3 and 4). The share of black alder has decreased in the observed period. The heavy soils and weed- covered sites in the forest of Kalje do not seem to be as conducive for this species as they are for narrow-leaved ash. Additional research should be made to shed more light on this problem. Other species of pioneer character are the elements that fill the gaps in the stand canopies and increase their diversity. Depending on the height, cleaning or thinning treatments should be directed at ensuring an adequate share of "other" species in the species mix and not at removing them completely. This refers particularly to Tatarian maple, elm, spreading elm, common hornbeam, hedge maple and wild pear. The analyses were made in the localities in which dieback in former pedunculate oak stands affected over one third of the volume, or 36 to 77 %. The results do not show a significant influence of dieback intensity of former oak stands on the structural characteristics of the present young growth. This means that for the moment, regardless of the degree and rate of dieback in the former stands, the young stands do not differ from each other. Accordingly, pioneer tree species should dominate in restorative silvicultural treatments undertaken to mitigate the consequences of intensive dieback (more than one third of basic volume) and sudden site degradation. The results show that restoration was successful from a silvicultural aspect. New stands have been established which will fulfil their non-commercial and commercial role in the forest Kalje. Natural regeneration of pedunculate oak under the shelter of pioneer species points to a gradual site rehabilitation and a long-term transitional character of these stands. It should be stressed that this research is a contribution to the currently held attitude that a degraded site is lost for this tree species. Key words: Quercus roburZ., Fraxinus angustifolia Vahl, dieback, pioneer tree species, site degradation, site rehabilitation Šumarski list br. 11-12. CXXVI (2002), 575-587 |