Drought-induced shift in tree response to climate in floodplain forests of Southeastern Europe

Abstract

Floodplain forests are the most rapidly disappearing ecosystem in the world, especially in temperate regions of Europe where anthropogenic influence has been pronounced throughout history. Research on primeval forests is crucial to further our understanding of their natural dynamics and interaction with climate but is limited by the lack of such preserved forests. The aim of this study was to investigate how a primeval floodplain forest in Southeastern Europe has responded to climate variability during the last 250 years through comparison of tree growth and climate, canopy disturbance and recruitment dynamic of two dominant tree species with different tolerances to flooding/drought. Our analysis revealed induced stress caused by several consecutive severe drought events in the 1940s, which led to a significant increase in sensitivity to increasing temperatures and decreasing river water levels. This trend is particularly pronounced in pedunculate oak. Age structure analysis revealed one larger episode of oak regeneration culminating after periods of intense growth release. Such period co-occurs with summer drought, which is part of a complex system of natural disturbances and a significant natural driver of the cyclical regeneration of primeval oak ecosystems.

Candidate gene SNP variation in floodplain populations of pedunculate oak (Quercus robur L.) near the species' southern range margin: Weak differentiation yet distinct associations with water availability

“…These concerns are corroborated by reports regarding the negative impacts of such environmental changes on the performance of floodplain pedunculate oak forests (Mikac et al, 2018;Stojanović, Levanič, Matović, & Orlović, 2015). Thus, populations from this area currently exhibit increased ecological marginality owing to water deficit.…”

Bottomland hardwood forest growth and stress response to hydroclimatic variation: Evidence from dendrochronology and tree-ring δ<sup>13</sup>C values

“…CC BY 4.0 License. Gao et al, 2018;Mikac et al, 2018;Szejner et al, 2020). Through these studies, a strong positive relationship between growth rates and precipitation has been well-established.…”

The legacy of management approaches and abandonment on old-growth attributes in hardwood floodplain forests in the Pannonian Ecoregion

“…In Europe, one of the key distribution areas of surviving remnants of near-natural forests is Eastern Europe (Forest Europe 2015;Mikac et al 2018;Sabatini et al 2018), where substantial old, near-natural stands also exist in the matrix of commercially managed forests, outside strictly protected areas (Drescher et al 2003;Prots 2010).…”

“…Table S1). According to the recent literature, Q. robur has the potential to reach a DBH of 200-260 cm, and there can be up to 17-25 very large trees ha −1 (Bobinac 2000;Vrška et al 2006;Mikac et al 2018). Taking into consideration both the historical and the recent reference literature on the number and density of very large trees, it is possible to conclude that even the oldest oak forest we studied (180 years) cannot be regarded as a true old-growth forest, given the number of very large trees.…”

“…• Due to a lack of flooding and low water table, the structure and composition of many hardwood floodplain forests are changing (Mikac et al 2018). Rehabilitation of a more natural water regime would be a key factor in guaranteeing the future of these forests at landscape level.…”