Spring temperature responses of oaks are synchronous with North Atlantic conditions during the last deglaciation

Abstract

Paleoclimate proxies based on the measurement of xylem cell anatomy have rarely been developed across the temperature range of a species or applied to wood predating the most recent millennium. Here we describe wood anatomy‐based proxies for spring temperatures in central North America from modern bur oaks (Quercus macrocarpa Michx.). The strong coherence of temperature signals across the species range supports the use of these proxies across thousands of years of climatic change. We also used 79 subfossil oak log cross sections from northern Missouri, 14C‐dated to 9.9–13.63 ka (ka is 1000 cal yr BP), to assess the frequency of oak deposition into alluvial sediments and a subset of these oaks for a wood anatomy‐based reconstruction of spring paleotemperatures. Temperatures during the Younger Dryas cold period (YD) were up to 3.5°C lower than modern temperatures for that region, equivalent to or lower than those experienced at the northern edge of the modern species range. Compared to extant oaks growing at much higher [CO2], subfossil oaks had greater vessel frequencies. Besides very low theoretical (or estimated) xylem conductivity near the beginning of the oak record near 13.6 ka, vessel frequencies greater than modern trees compensated for reduced vessel dimensions so that theoretical xylem conductivity was consistently above that of modern trees at the cold northern sites. Significant correlations were found between the frequency of 14C‐dated oaks and either δ18O from the NGRIP (North Greenland Ice Core Project) ice core or from the Cariaco grayscale marine‐sediment record from the southern Caribbean sea. Oak deposition into alluvial sediments during the YD was significantly lower than expected given the average sample depth of oaks from 9.9 to 13.6 ka. Reduced oak deposition during the YD suggests that an abrupt shift in climate reduced oak populations across the region and/or changed the rates of channel movement across drainages.

Drivers of radial growth and carbon isotope discrimination of bur oak (Quercus macrocarpa Michx.) across continental gradients in precipitation, vapour pressure deficit and irradiance

“…In turn, these differences reflect the rings of SD oaks being composed of a greater proportion of earlywood, derived from the use of non‐structural carbon reserves stored during the previous growing season as earlywood forms during the spring before leaves are expanded (Voelker et al . and references therein ). This notion is supported by RWI of SD bur oaks, but not those from MO or WI, showing significant correlations with the previous year's climate ( data not shown ), a finding that is often associated with upland oak species (Stahle & Hehr ; White et al .…”

The effect of subambient to elevated atmospheric CO2 concentration on vascular function in Helianthus annuus: implications for plant response to climate change

“…By contrast, relatively few studies have examined the water relations and/or the gas-exchange response of plants grown across [CO 2 ] atm gradients that include subambient [CO 2 ] atm (Bunce & Ziska, 1998;Cowling & Sage, 1998;Maherali et al, 2002;Polley et al, 2002;Bunce, 2006Bunce, , 2007Gerhart & Ward, 2010;Phillips et al, 2011). However, evaluating plant responses along a continuum of [CO 2 ] atm can reveal the degree to which plasticity can accommodate the predicted future rise in [CO 2 ] atm , broaden the interpretative power of fossil wood and growth rings, inform predictions of plant biogeography under elevated [CO 2 ] atm and add further insight to studies of xylem evolution (Sperry, 2003;Pittermann, 2010;Fonti & Jansen, 2012;Voelker et al, 2012). Hence, the goal of this study was to contribute an organismal perspective on the hydraulic effects of [CO 2 ] atm , with the hypothesis that [CO 2 ] atm forcing will shift xylem function in a manner consistent with changes in leaf-level demand for water.…”

Wood Anatomy and Plant Hydraulics in a Changing Climate

“…Tree ring records indicate that many wood anatomical components are sensitive to climate parameters during the years in which they are formed, which suggests that these anatomical differences could affect hydraulics over time (Fonti et al 2010;Olano et al 2013). For example, wood density has been shown to increase in oak trees in years following a severe drought (Corcuera et al 2004) and an analysis of contemporary and paleoclimate effects on vessels in Quercus macrocarpa tree rings showed a significant positive relationship between spring temperatures and earlywood vessel diameter and conductivity (Voelker et al 2012). The number of functional xylem rings will also determine the degree of potential plasticity of hydraulic architecture in response to changes in climate.…”

“…The number of functional xylem rings will also determine the degree of potential plasticity of hydraulic architecture in response to changes in climate. For example, in the oaks described above, the species' water transport relies strongly upon xylem formed in the same year, giving rise to high plasticity in response to climate (Voelker et al 2012). Anatomical studies have indicated that individual rings differ in their hydraulic properties and vulnerability to embolism (Melcher et al 2003).…”