The influence of climate change on the dynamics of pedunculate oak (Quercus robur L.) and narrow-leaved ash (Fraxinus angustifolia Vahl) forests in Croatia

Klimatske promjene očituju se sveukupnim porastom temperature zraka i značajnom promjenom rasporeda i količine oborina (Auer i sur., 2007; IPCC 2014; Gao i Giorgi, 2008). Nadalje, klimatske promjene obilježene su povećanom frekvencijom ekstremnih događaja (suše, poplave, razorni vjetrovi) koji su glavni uzrok prirodnih nepogoda (Beniston i sur., 2007; Lenderink and Van Meijgaard, 2008). Nizinski poplavni šumski ekosustavi jedni su od najosjetljivijih na promjene klime (Horner i sur. 2009; Pittock i sur. 2008) jer direktno ovise o hidrološkom režimu nizinskih rijeka. Prirodne nizinske poplavne šume prašumskog karaktera u Europi praktički više ne postoje (Sabatini i sur., 2018). Takve šume smatraju se jednim od dva najugroženija šumska stanišna tipa (Schnitzler, 1994; Cox i Temple, 2016). Hrast lužnjak (Quercus robur L.) i poljski jasen (Fraxinus angustifolia Vahl) vrste su koje dominiraju u nizinskim šumama jugoistočne Europe pa tako i Hrvatske. Cilj ovoga istraživanja bio je utvrditi utjecaj klimatskih čimbenika na dinamiku sastojina hrasta lužnjaka i poljskog jasena na području Posavine, s naglaskom na različite mikrostanišne uvjete (bara, niza, greda). Također, željelo se utvrditi postoji li razlika u klimatskoj osjetljivosti dobivenih kronologija hrastova sa postojećim europskim kronologijama te istražiti potencijal kronologija hrasta lužnjaka iz prašumskih sastojina. Rezultati klimatskih korelacija otkrivaju postojanje dvije potpuno odvojene grupe hrastova prema klimatskoj osjetljivosti (istočna i zapadna) i četiri grupejasena unutar područja srednje Posavine (zapad). Poljski jasen iz reljefno najnižih dijelova (bara) najviše je osjetljiv na klimatske čimbenike i najviše ugrožen klimatskim promjenama, dok je kod hrasta situacija povoljnija. U usporedbi s europskim kronologijama hrastovi su manje osjetljivi na klimatske čimbenike i tvore zasebnu grupu zajedno s nekim kronologijama iz okruženja. Kronologije prašumskih sastojina pokazuju veliki potencijal u rekonstrukciji ekstremnih događaja kroz povijest te rekonstrukciji pojedinih klimatskih čimbenikaClimate change is manifested by an overall increase in air temperature and a significant change in the distribution and amount of precipitation (Auer et al., 2007; IPCC 2014; Gao and Giorgi, 2008). Furthermore, it is characterized by an increased frequency of extreme events (droughts, floods, devastating winds) that are a major cause of natural disasters (Beniston et al., 2007; Lenderink and Van Meijgaard, 2008). Lowland floodplain forest ecosystems are among the most sensitive to climate change (Horner et al., 2009; Pittock et al., 2008) because they are directly dependent on the hydrological regime of lowland rivers. Natural floodplain forests with old-growth characteristics practically no longer exist in Europe (Sabatini et al., 2018). Such forests are considered one of the two most endangered forest habitat types (Schnitzler, 1994; Cox and Temple, 2016). Pedunculate oak (Quercus robur L.) and narrow-leaved ash (Fraxinus angustifolia Vahl) are species that dominate in the lowland forests of southeastern Europe, including Croatia. The aim of this study was to determine the influence of climatic factors on the dynamics of pedunculate oak and narrow-leaved ash stands in the Posavina area, with emphasis on different microhabitat conditions (wet, fresh, dry). Another aim was to determine whether there is a difference in climatic sensitivity of the obtained oak chronologies with the existing European chronologies and to investigate the potential of pedunculate oak chronologies from old-growth stands. The results of climatic sensitivity (eastern and western) and 4 groups of ash within the area of central Posavina (west). Narrow-leaved ash from the lowest parts (wet) is most sensitive to climatic factors and most vulnerable to climate change, while the situation with oak is more favorable. Compared to European chronologies, oaks are less sensitive to climatic factors and form a separate group together with some other chronologies from the region. Chronologies of old-growth stands show great potential in the reconstruction of extreme events throughout history and in the reconstruction of certain climatic factors. relations reveal the existence of 2 completely separate groups of oaks according to climati