Development of holm oak (Quercus ilex L.) stands in permanent test surfaces of National park Brijuni

Područje Brijunskog arhipelaga, zahvaljujući geomorfološko-hidrološkim, klimatskim, prirodnim i antropogenim utjecajima, tvori jedno od malobrojnih očuvanih jadranskih prirodnih, kulturnih i krajobraznih vrijednosti. Na području Velog Brijuna na relativno maloj površini izmjenjuju se elementi više šumskih stanišnih tipova. Antropogeni čimbenik je utjecao na nestanak dijelova šuma sječom i gradnjom infrastrukture. Drugi čimbenik je prekobrojno stanje divljači na otoku. Iz tih razloga formirane su dvije trajne pokusne plohe za praćenje ekosustava na Velikom Brijunu: jedna u ograđenom prostoru rezidencijalnog parka Bijele vile (br. 57) i druga u slobodnom prostoru u predjelu Mrtvi vrh (br. 56).Istraživanje na kojemu se temelji ovaj rad provedeno je u svibnju 2017. godine na obje trajne pokusne plohe, u sklopu čega su analizirana vegetacijsko-ekološka i strukturna obilježja tih sastojina. Dobiveni rezultati uspoređeni su s posljednjom cjelovitom izmjerom istih ploha iz 1988. godine. Na temelju obrađenih podataka utvrđene su velike razlike između mjerenih površina. Floristička slika dalje produbljuje razlike između ova dva lokaliteta. Na trajnoj pokusnoj plohi 56 gotovo uopće nema sloja grmlja, dok su na pokusnoj plohi 57 isti izrazito razvijeni. Nadalje, osim flornog osiromašenja na TPP 56 treba napomenuti i nemogućnost prirodnog pomlađivanja sastojine, dok je na TPP 57 evidentiran gust ponik i pomladak. S obzirom na mjerene elemente strukture sastojine 1988. i 2017. godine, sastojina na TPP 57 prirodno se razvija i raste dok je sastojina na TPP 56 zbog velikog utjecaja divljači u fazi regresije i degradacije.Ponajprije je potrebno na dijelu otoka smanjiti broj alohtone divljači i svesti njezin broj na održivost staništa. Površinu TPP 57 i okolno područje zaštititi kao posebni rezervat šumske vegetacije i provoditi mjere u okviru te kategorije zaštite.
The area of the Brijuni archipelago, due to geomorphological-hydrological, climatic, natural and anthropogenic influences, makes up one of a few preserved natural, cultural and landscape values in the Adriatic. In the area of Veli Brijun, there are alternating elements of several forest stand types on a relatively small surface. The anthropogenic factor influenced the disappearance of parts of forests through logging and infrastructure construction. The second factor is excessive numbers of wildlife on the island. Consequently, two test surfaces were formed intended for ecosystem monitoring on the island of Veliki Brijun: one in the fenced area of the residential park of the White Villa (No. 57) and the other in the free space in the area referred to as the Dead Peak (No. 56). The research behind this paper was conducted in May 2017 on both permanent experimental plot within which vegetative-ecological and structural features of these stands were analysed. The obtained results were compared with the most recent previous measurement of the same surfaces conducted in 1988. Based on the processed data, huge differences were identified between the measured surfaces. The floristic aspect further accentuates the differences between the two localities. In the permanent experimental plot No. 56, there is hardly any shrub layer, while in the permanent experimental plot No. 57 the latter is extremely developed. Moreover, in addition to floral scarcity on the permanent experimental plot No. 56 it is important to highlight the impossibility of natural stand regeneration, while on the permanent experimental plot No. 57 dense sprouts and young growth were recorded. Considering the measured elements of stand structure in 1988 and in 2017, the stand in the permanent experimental plot No. 57 develops and grows naturally, while the stand in the permanent experimental plot No. 56 is undergoing a phase of regression and degradation due to a large influence of wildlife. First of all, the numbers of allochthonous wildlife in the specific part of the island need to be reduced to numbers that enable stand sustainability. The permanent test surface No. 57 and the surrounding area need to be preserved as a special forest vegetation reserve and measures need to be implemented within this protection category.