Central-European mountain spruce ( Piceaabies (L.) Karst.) forests: regeneration of tree species after a bark beetle outbreak

Abstract

In the 1990s, a bark beetle ( Ips typographus) outbreak caused a dieback of semi-natural mountain spruce ( Picea abies) forests in the Šumava National Park (Czech Republic). Two different approaches were applied to the attacked forests: (1) a small portion of the stands in the core zone of the national park was left without intervention, relying upon natural regeneration, and (2) traditional technical measures were adopted, in which attacked trees were felled and removed. Under the dead canopy of the stands left without intervention, there was a good regeneration of spruce and rowan ( Sorbus aucuparia) and, sporadically, beech ( Fagus sylvatica). In clear-cut areas, the numbers of spruce and rowan were significantly lower than under the dead canopy. Pioneer species such as willow ( Salix aurita), birch ( Betula pubescens), and aspen ( Populus tremula) appeared in the clear-cut areas. The dependence of spruce regeneration on the availability of suitable microhabitats was found: decaying wood and spruce litter was found as the most favourable. The results confirmed that the original tree species of the mountain spruce forests regenerate well under dead canopy. The bark beetle outbreak does not result in the complete loss of the forests and could even be considered as a tool for the restoration of their natural character.