Frequency and characteristics of severe storms in the Urals and their influence on the development, structure and management of the boreal forests

Abstract

After an unusual number of storms in the Urals in the early 1990s and with the global warming over the past 100 years, there were fears of increasing storm frequency in this region. This study investigates meteorological data, aspects of windthrow and the beginnings of reforestation after windthrow under different silvicultural treatments. The meteorological data were collected from a region covering an area of over 20 million ha of the Urals to the west and to the east. Storm frequency was analysed for 1946-1996 and windthrow events for 1965-1996, according to the availability of data. Regeneration experiments were begun on two experimental plots of 20 and 12 ha, respectively. Each was divided into three sub-plots, one being left untouched, one roughly logged and the last roughly logged and then replanted. Mean temperatures in the Urals showed a rise during the last more than 100 years, indeed, but neither the annual number of storms nor their mean wind speed increased. Only a few forest enterprises suffered windthrow on more than 1% of their total area. Most of the windthrown trees were of medium height and diameter. With two exceptions none of the storms greatly altered the structure of the forests. With over 3700 trees taller than 20 cm and up to 11 species, the forests showed great diversity. Neither windthrow, nor logging and clearing diminished the diversity, but all reduced the abundance of most of the species. These forests, left to regenerate naturally for some decades after clear-cutting, show a much higher number of species and individual trees than intensively managed conifer forests in the Swiss Alps. Therefore, it is recommended that natural development processes be more often integrated into conventional forest management methods. (C) 2000 Elsevier Science B.V.