Disturbance history and forest development of windthrow gaps in the Perućica old-growth forest

V pragozdu Perućica v Bosni in Hercegovini smo raziskali vpliv treh srednjepovršinskih vetrolomov na razvoj gozdov v vetrolomnih vrzelih. Na vsaki vetrolomni površini smo postavili tri raziskovalne ploskve, velikosti 25 x 25 m. Na enak na%in smo postavili raziskovalne ploskve v kontrolnih sestojih. Na raziskovalnih ploskvah na vetrolomih smo izmerili vsa stoje%a drevesa in mladovje. Na vsaki raziskovalni ploskvi na vetrolomu smo odvzeli izvrtke desetim drevesom, ki so bila najbliţje središ%u ploskve. Izvrtke smo odvzeli tudi desetim drevesom ve%jih dimenzij na celotni površini vetroloma. Izmerili smo vsa razpadajo%a drevesa ter jih razvrstili v pet razredov glede na stopnjo razgradnje. Zgradba sestojev se je po vetrolomih spremenila. Svetloljubni listavci se pojavijo, %e je dovolj svetlobe, v nasprotnem primeru se pojavi bukev. Najprej se pojavijo svetloljubni listavci, za njimi bukev in šele na koncu jelka. Vsak vetrolom je posledica ene ve%je ujme. Nastala vrzel se je po ujmi po%asi širila. Na vetrolomih Osoje in Tunjemir se je pestrost drevesnih vrst pove%ala, ne pa tudi na vetrolomu Skakavac. Mladje svetloljubnih listavcev se je pojavilo po vetrolomih, mladje sencozdrţnih drevesnih vrst je bilo prisotno ţe pred motnjami. Bukev bolj odreagira na pove%an dotok svetlobe kot jelka. Povpre%ni debelinski prirastek gorskega javorja je najve%ji pri drevesih, ki so vzklila po vetrolomu. Srednjepovršinski vetrolomi pomembno vplivajo na razvoj gozdov.In the Perućica old-growth forest in Bosnia and Herzegovina, we investigated the impact of three intermediate wind disturbances upon the forest development of windthrow gaps. Three research areas 25 x 25 m were prepared in each windthrow gap. Research areas were prepared in the same way also in control stands. In the research areas, all standing trees and young growths were measured. In each research area in the windthrow gaps, core samples were taken from ten trees that were closest to the centre of the area. Core samples were taken also from ten larger trees in the entire windthrow surface. All decaying trees were measured and they were classified into five classes, depending on the level of decomposition. The structure of stands changed after windfall. Deciduous trees that prefer ample light conditions appear in case of ample light, otherwise beeches apper. First, decidiuous trees appear, followed by beeches and finally by firs. Each windfall results from a larger natural disaster. A gap caused by a natural disaster spreads slowly. In windfalls Osoje and Tunjemir, the variety of tree species increased, which does not apply for the windfall Skakavac. The growth of decidiuous trees that prefer ample light conditions appeared after wind disturbances, whereas the growth of shade-tolerant tree species was present already before the disturbances. Beeches reacts more strongly to more ample light than firs. The average radial growth of sycamore maple is largest in case of trees that germinated after the wind disturbance. Intermediate wind disturbances have a significant impact upon forest development