The 2018 European heatwave led to stem dehydration but not to consistent growth reductions in forests

Publisher Copyright: © 2022, The Author(s).Heatwaves exert disproportionately strong and sometimes irreversible impacts on forest ecosystems. These impacts remain poorly understood at the tree and species level and across large spatial scales. Here, we investigate the effects of the record-breaking 2018 European heatwave on tree growth and tree water status using a collection of high-temporal resolution dendrometer data from 21 species across 53 sites. Relative to the two preceding years, annual stem growth was not consistently reduced by the 2018 heatwave but stems experienced twice the temporary shrinkage due to depletion of water reserves. Conifer species were less capable of rehydrating overnight than broadleaves across gradients of soil and atmospheric drought, suggesting less resilience toward transient stress. In particular, Norway spruce and Scots pine experienced extensive stem dehydration. Our high-resolution dendrometer network was suitable to disentangle the effects of a severe heatwave on tree growth and desiccation at large-spatial scales in situ, and provided insights on which species may be more vulnerable to climate extremes.Peer reviewe

Mass spectra of an unknown peak eluted in the fifth minute of HPLC analysis of olomoucine II transport.

<p>(A) spectrum in positive mode, (B) MS² in positive mode, (C) negative mode, (D) MS² in negative mode. Based on the nominal mass shift (+80 Da) from parent compound and the collision spectra in negative as well as positive mode the compound was identified as a sulfated conjugate of olomoucine II.</p

Chemical structures of olomoucine II and purvalanol A.

<p>Chemical structures of olomoucine II and purvalanol A.</p

Chromatograms of samples from MDCKII-par cells six hours after olomoucine II addition.

<p>(A) olomoucine II was added into apical compartment while olomoucine II and its sulfated conjugate were analyzed in acceptor basolateral compartment, (B) olomoucine II was added into apical compartment while olomoucine II and its sulfated conjugate were analyzed in donor apical compartment, (C) olomoucine II was added into basolateral compartment while olomoucine II and its sulfated conjugate were analyzed in acceptor apical compartment, (D) olomoucine II was added into basolateral compartment while olomoucine II and its sulfated conjugate were analyzed in donor basolateral compartment. This analysis with end point samples was performed for all olomoucine II transport experiments.</p

Time-dependent generation of sulfated conjugate of olomoucine II in MDCKII-ABCG2 (A, D, G), MDCKII-ABCB1 (B, E, H) and MDCKII-par (C, F, I) cells and its distribution into the apical and basolateral compartments.

<p>Relative quantification of sulfated olomoucine II was calculated as a ratio between peak area of sulfated olomoucine II and the peak area of internal standard (IS). 5 µM fumitremorgin C (FTC), a specific ABCG2 inhibitor, was used in MDCKII-ABCG2 cells for the assessment of possible involvement of ABCG2 in the transport of sulfated metabolite. 1 µM LY335979 (LY) was employed as a specific ABCB1 and endogenous canine Abcb1 inhibitor in MDCKII-ABCB1 and MDCKII-par cells, respectively. Data come from transport experiments with olomoucine II at concentrations of 100 nM (A, B, C), 1 µM (D, E, F) and 10 µM (G, H, I). In basolateral to apical transport direction, olomoucine II was added into the basolateral compartment and its sulfate conjugate was determined in the apical compartment. In the opposite transport direction, olomoucine II was applied into the apical compartment and its sulfated metabolite was analyzed in the basolateral compartment. ▴, transport into apical compartment without inhibitor; ▾, transport into basolateral compartment without inhibitor; ▵, transport into apical compartment with inhibitor; ▿, transport into basolateral compartment with inhibitor. Values are expressed as means ± SD of three independent experiments.</p

Transport of olomoucine II at concentrations of 100(A, B, C), 1 µM (D, E, F) and 10 µM (G, H, I) across monolayers of MDCKII-ABCG2 (A, D, G), MDCKII-ABCB1 (B, E, H) and MDCKII-par (C, F, I) cells.

<p>5 µM fumitremorgin C (FTC) was used as a specific ABCG2 inhibitor in MDCKII-ABCG2 cells. 1 µM LY335979 (LY) was employed as a specific ABCB1 and endogenous canine Abcb1 inhibitor in MDCKII-ABCB1 and MDCKII-par cells, respectively. Ratios of olomoucine II transport across cell monolayers (olomoucine II transport in basolateral to apical direction divided by transport in apical to basolateral direction) with or without inhibitor were calculated two hours after olomoucine II addition and statistically compared (see insets). Due to the generation of sulfated conjugate of olomoucine II, transport ratios were determined at 2 h interval to reduce the misrepresenting effect of the metabolite. In basolateral to apical transport direction, olomoucine II was added into the basolateral compartment and its concentrations were determined in the apical compartment. In the opposite transport direction, olomoucine II was applied into the apical compartment and its concentrations were analyzed in the basolateral compartment. ▴, basolateral to apical transport without inhibitor; ▾, apical to basolateral transport without inhibitor; ▵, basolateral to apical transport with inhibitor; ▿, apical to basolateral transport with inhibitor. Data are expressed as means ± SD of three independent experiments. *p<0.05; **p<0.01; ***p<0.001.</p

Transport of purvalanol A at concentrations of 1 µM (A, B, C) and 10 µM (D, E, F) across monolayers of MDCKII-ABCG2 (A, D), MDCKII-ABCB1 (B, E) and MDCKII-par (C, F) cells.

<p>5 µM fumitremorgin C (FTC) was used as a specific ABCG2 inhibitor in MDCKII-ABCG2 cells. 1 µM LY335979 (LY) was employed as a specific ABCB1 inhibitor in MDCKII-ABCB1 cells. Ratios of purvalanol A transport across cell monolayers (purvalanol A transport in basolateral to apical direction divided by transport in apical to basolateral direction) with or without inhibitor were calculated and statistically compared (see insets). Transport ratios were determined 6 h after purvalanol A addition. In basolateral to apical transport direction, purvalanol A was added into the basolateral compartment and its concentrations were determined in the apical compartment. In the opposite transport direction, purvalanol A was applied into the apical compartment and its concentrations were analyzed in the basolateral compartment. ▴, basolateral to apical transport without inhibitor; ▾, apical to basolateral transport without inhibitor; ▵, basolateral to apical transport with inhibitor; ▿, apical to basolateral transport with inhibitor. Data are expressed as means ± SD of three independent experiments.</p