Resistance of native oak to recurrent drought conditions simulating predicted climatic changes in the Mediterranean region

Abstract

The capacity of a Quercus pubescens forest to resist recurrent drought was assessed on an in situ experimental platform through the measurement of a large set of traits (ecophysiological and metabolic) studied under natural drought (ND) and amplified drought (AD) induced by partial rain exclusion. This study was performed during the third and fourth years of AD, which correspond to conditions of moderate AD in 2014 and harsher AD in 2015, respectively. Although water potential (Ψ) and net photosynthesis (Pn) were noticeably reduced under AD in 2015 compared to ND, trees showed similar growth and no oxidative stress. The absence of oxidative damage could be due to a strong accumulation of α-tocopherol, suggesting that this compound is a major component of the Q. pubescens antioxidant system. Other antioxidants were rather stable under AD in 2014, but slight changes started to be observed in 2015 (carotenoids and isoprene) due to harsher conditions. Our results indicate that Q. pubescens could be able to cope with AD, for at least 4 years, likely due to its antioxidant system. However, growth decrease was observed during the fifth year (2016) of AD, suggesting that this resistance could be threatened over longer periods of recurrent drought.

Exogenous Isoprene Confers Physiological Benefits in a Negligible Isoprene Emitter (Acer monspessulanum L.) under Water Deficit

“…During fumigation, saplings were enclosed in two dynamics chambers of 77 L volume (77 cm height, 35 cm diameter) and PTFE-made (Polytetrafluoroethylene), based on our previous models [17,22,23] ( Figure 5) (Figure 5a,b). Each chamber was enclosed using a Nalophan film (MediSense, UK).…”

“…In Mediterranean forests, two tree species, Acer monspessulanum L. and Quercus pubescens Wild., coexist together in mature forests with a remarkable tree density in some forests [17] implying that their canopies are intertwined. Both species are also known for their remarkable resistance to drought [22,23] while they feature contrasting capacities to emit isoprene. A. monspessulanum releases negligible isoprene emission rates (0.3 µg.g −1 .h −1 ) or any other terpene [17], while Q. pubescens is the major isoprene emitter in the Mediterranean region (~100 µg.g -1 .h −1 ) [24].…”

Response of Downy Oak (Quercus pubescens Willd.) to Climate Change: Transcriptome Assembly, Differential Gene Analysis and Targeted Metabolomics

“…In a previous study carried out on the site of O 3 HP, a two-fold increase in stomata closure was found in spring from Q. pubescens of the rain exclusion treatment as compared to the control plot [ 29 ].…”

“…Summer stomatal conductance was significantly reduced to 56% in control as compared to the rain exclusion plot with a concomitant reduction of net photosynthesis [ 29 ]. Hence, it is probable that the decrease in phosphate ion transmembrane transporter activity reflects a balance of the redox state between photosynthesis light reactions and the Calvin cycle.…”

The Interplay Between Ozone and Urban Vegetation—BVOC Emissions, Ozone Deposition, and Tree Ecophysiology

“…The variable responses reported previously emphasize that BVOC emissions under drought are highly dependent on tree species (sensitivity) as well as the intensity and temporal extend of the stress events (Dani et al, 2015). Different effects are thus explained by species sensitivity as well as drought intensity (Niinemets, 2010;Klein, 2014;Saunier et al, 2018). For example, the same species can possess an increase of isoprene emissions under mild drought while severe drought decreases emissions (Brilli et al, 2007;Genard-Zielinski et al, 2014;Dani et al, 2015).…”