Turkey oak (Quercus cerris L.) is more drought tolerant and better reflects climate variations compared to pedunculate oak (Quercus robur L.) in lowland mixed forests in northwestern Serbia: A stable carbon isotope ratio (δ13C) and radial growth approach

Highlights

• Stable carbon isotope ratio (δ¹³C) in latewood of tree rings is a better drought proxy than tree-ring width (TRW).

• Quercus cerris exhibited better drought tolerance (<δ¹³C) than Quercus robur.

• Quercus robur and Quercus cerris have different δ¹³C response to drought, while their TRW response is comparable.

• TRW and δ¹³C correlate more strongly with drought indices than with raw meteorological data.

Abstract

Tree-ring width (TRW), stable carbon isotope ratio (δ¹³C) and intrinsic water use efficiency (iWUE) data set chronologies were built for the period 1961–2000 for two oak species (pedunculate oak – Quercus robur L. and Turkey oak – Quercus cerris L.) in northwestern Serbia (Vojvodina province). We focused on the response of the two oak species to measured meteorological data (temperature, precipitation and cloud cover), drought events expressed by six meteorological drought indices, and river water level to better understand their drought tolerance and stress and to assess the reliability of the species response to climate and drought indices when using TRW or δ¹³C. Turkey oak exhibited better drought tolerance (and less drought stress) compared to pedunculate oak, as manifested, respectively, by less negative δ¹³C and lower iWUE values. Based on a generalised additive mixed model (GAMM) among the six drought indices studied, the standardised precipitation evapotranspiration index and the standardised precipitation index showed the best fit with both TRW and δ¹³C, while the Palmer drought severity index exerted a strong influence only on TRW. It was thus concluded that δ¹³C responds more strongly and rapidly to climate variations than TRW.