engleski

The structure and possibility of natural regeneration in the managed and non-managed beech and fir forests in Croatia

Background and Purpose: The paper presents results of comparison of structural elements that have an impact on natural regeneration and viability in non-managed and managed uneven-aged forests. Basic structural indicators, structure of tree crowns and regenerative potential have been recorded. The vertical stand profile with trees measured on the field has been made by the application of digitalization. Too many overmature trees, complete absence of young tress in the thinnest diameter classes, as well as shortage of medium thick fir trees are indicators of disturbed natural structure. In addition, there is an excessive crown cover over soil of almost 90% and low quality and old young growth of beech in the shrubbery layer, which ultimately results in absence of natural regeneration and questionable capacity for sustainability of these stands. Continuous natural regeneration is the fundamental condition for the existence of adequate structure in the preservation of biological diversity of beech and fir forests. Materials and Methods: Two permanent experimental plots, 100 by 100 m, were laid out. All trees larger than 7.5 cm in diameter were marked by numbers, and basic data recorded (diameter at breast height, tree heights and stem lengths). A sub-plot, 60 x 60 m in size, was set up in the most homogeneous part of the plot. Horizontal projections of tree-crowns were recorded for all trees on the sub-plot. Crown projections were digitalized, and a vertical stand profile was made. The structure and numbers of young growth, as well as of the shrub layer were recorded on an area of 360 m2 (three strips, 2 x 60 m) within each subplot. Results and discussion: Distribution of the number of trees indicates the absence of fir of the smallest diameter degrees, and the absence of medium diameter trees and an excessive number of large-diameter trees in the both, non-managed and managed forests. In the smallest diameter degrees beech filled in the lack of fir trees. Digital models of tree crown projections and vertical profiles of the stands indicate very dense canopy of the beech in the second layer, which prevents normal natural regeneration of the fir. Conclusions: The results presented suggest the questionability of satisfactory natural regeneration and survival of these stands. The models of tree crown projections enable permanent computer-digital monitoring of changes in the stand structure, their simulation and open new possibilities in the study of stand structure.

uneven-aged forest; stand structure; non-managed forests; managed forests; natural regeneration; crown cover over soil; digitalization of crowns; fir; beech

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