Review of oak (Quercus spp.) decline in Europe and in Slovenia

Namen raziskave je bil s pregledom domače in tuje literature določiti najpomembnejše abiotske in biotske dejavnike odmiranja doba (Quercus robur), gradna (Q. petraea) in črnike (Q. ilex) v Evropi ter pri nas, in jim določiti nivo v Manionovi spirali propadanja. Pregledu literature je sledila še analiza podatkov Zavoda za gozdove Slovenije o poseku gradna in doba v obdobju 1995–2022 na območju Slovenije. Po pregledu literature smo zaključili, da na odmiranje gradna, doba in črnike vpliva kompleks abiotskih in biotskih škodljivih dejavnikov. Pri dobu in gradnu se kot poglaviten dejavnik predispozicije in hkrati tudi sprožilni dejavnik najpogosteje omenja sušni stres, katerega vpliv postaja s spreminjanjem podnebja vedno večji, od biotskih dejavnikov pa predvsem različne vrste gliv in fitoftor ter vnos najrazličnejših tujerodnih vrst (npr. podlubnikov). Varstveno-sanacijski posek in posek oslabelega drevja je v proučevanem obdobju pri dobu znašal kar približno 35 % skupne količine poseka oz. približno 204.000 m3, pri gradnu pa približno 27 % oz. približno 1.109.000 m3. Pri črniki se za razliko od gradna in doba glede ogroženosti bolj kot pomen abiotskih poudarja pomen biotskih dejavnikov, in sicer nekaterih vrst fitoftor in gliv. Abiotski dejavniki (predvsem suša) sicer v kombinaciji z biotskimi dejavniki prav tako predstavljajo pomemben vzrok za odmiranje črnike, vendar so v tem primeru bolj v vlogi dejavnikov predispozicije kot sprožilnih dejavnikov. Stanje črnike v Sloveniji trenutno bolj kot vse našteto v bistvu ogroža njena redkost.The aim of this study was to determine the most important abiotic and biotic factors that contribute to the decline of sessile (Quercus robur), pedunculate (Q. petraea) and holm oak (Q. ilex) in Europe and in Slovenia and to determine their role in Manion\u27s decline disease spiral by reviewing the scientific literature. To further determine the situation of sessile and pedunculate oak in Slovenia we analysed the data from Slovenian Forest Service regarding the felling of both oaks in the period from 1995 to 2022. After the literature review we concluded that the decline phenomena of sessile, pedunculate and holm oak is caused by a complex of biotic and abiotic factors. As the main predisposing and at the same time inciting factor in sessile and pedunculate oak decline the literature mentions drought that is being enchanced with the changing climate. From biotic factors different species of fungi, phytopthora and introduced invasive species are mentioned (as bark beetles). The sanitation felling of sessile oak in analysed period accounted for approximately 35 % (204.000 m3) of all felling of sessile oak and the sanitation felling of pedunculate oak accounted for approximately 27 % (1.109.000 m3) of all felling of pedunculate oak. In the decline of holm oak the biotic factors play the crucial role, especially some phytophthora and fungi species. Abiotic factors (especially drought) are mentioned more as a predisposing than inciting factors in holm oak decline. Holm oak status in Slovenia is more than by any other factor endangered simply because of its rarity