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Changes in horizontal structure of natural beech forests on an altitudinal gradient in the Sudetes

100%

Vacek Z. , Vacek S. , Bilek L. , Remes J. , Stefancik I.

tom 73

The article describes horizontal structure of the tree layer, natural regeneration, snags and crown projections of natural beech stands on three permanent research plots in the wide altitudinal range in the Krkonoše Mts (Czech Republic). The spatial structure was classified from 1980 to 2010 and subsequently the prediction of spontaneous development with an outlook for 30 years (to 2040) was done by growth simulator. Hopkins-Skellam index, Pielou-Mountford index, Clark-Evans index and Ripley’s K-function were calculated. Further, the vertical structure and total diversity index was evaluated. The horizontal structure of individuals in the tree layer had not changed significantly during the monitored years. Tree spatial pattern of the lowest altitude lying herb-rich beech forest was mostly regular to random, in acidophilous mountain beech forest predominantly random and in fragments of beech groups around the timberline aggregated. Juvenile growth on all investigated plots was distributed aggregated and snags randomly. The horizontal structure of crown projection centroids had always higher values toward the regularity than tree layer and was random to regular. The result of principal component analysis also confirmed that spatial pattern was dependent on the altitude, but also on the number of trees.

The effects of climatic conditions and forest site types on disintegration rates in Picea abies occurring at the Modrava Peat Bogs in the Šumava National Park

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Krejci F. , Vacek S. , Bilek L. , Mikeska M. , Hejcmanova P. , Vacek Z.

2013

tom 70

A survey of mountain spruce stand development in the Šumava National Park on Modrava peat bogs on an area of 1,370 ha resulting from spruce bark beetle outbreaks was performedby means of visual evaluation of aerial photographs from the period 1991–2000. In addition, our study addressed the influence of climatic effects (period1984–2000) andthe effect of forest site (climax, waterloggedandpeaty spruce stands) on the dynamics of disintegration of forest stands. We showed that new infestations were predominantly foundat short distances from their source, the average value was estimatedto be 40–60 m, whereas the longest distance for annual progress in west to east direction was estimated to be 120 m. Differences in the dynamics of disintegration between waterlogged stands and drier stands were confirmed. There was a positive relationship between the average temperature in the 2nd quarter of monitoring years which was registered as the period of the onset of bark beetle development and the proportion of degraded area in Norway spruce stands. Moreover, pronounced winter desiccation in January 1993 was a triggering mechanism with crucial importance for the outbreak of bark beetle in the studied area.