Inventory of rodent damage to forests

Conversion of coniferous monocultures to more stable mixed stands is one of the crucial tasks of present forestry in the Czech Republic. One of the factors hampering this process is the activity of small rodents that can cause severe damage to young plantations in winter. Little knowledge is still available of the ecology of small mammals in the forest environment and of the factors influencing their distribution and extent of damage. In order to acquire relevant information on rodent impacts on forest regeneration, we mapped the cumulated damage to forest plantations in 13 regions within the Czech Republic in 2007 and 2008. We checked 19,650 trees of eight species on 393 plots. Broadleaves were affected by browsing much more than conifers (20% and 4%, respectively). Of the monitored species, beech was damaged the most frequently (26% individuals). Browsing intensity differed among the regions (6-60% browsed individuals). The least damaged were the plantations at the altitudes below 400 m a.s.l.; on higher located plots the browsing intensity showed no trend. The proportion of damaged trees increased with plantation age up to 6 years, then it did not vary significantly. This study has confirmed that rodents are an important factor with a negative influence on the regeneration of broadleaves. Bark browsing in young trees is affected by several factors and the prediction of damage is complicated. Further research should improve the prediction of the bark browsing threat to young plantations and at the same time the efficiency of protection against rodent-caused damage.