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

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 degrees 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 delta 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.Keywords: Pleistocene, Quercus macrocarpa, Holocene, Pre-Boreal, Younger Dryas, Radiocarbon, Wood anatomy, Great Plains\, USA, Phenology, Bolling-Allerod, Xylem, Bur oa

Fire History at the Eastern Great Plains Margin, Missouri River Loess Hills

The purpose of this paper is to provide quantitative fire history information for a geographically unique region, the Loess Hills of northwest Missouri. We sampled 33 bur oak (Quercus macrocarpa Michx.), chinkapin oak (Q. muehlenbergii Engelm.), and black oak (Q. velutina Lam.) trees from the Brickyard Hill Conservation Area in northwest Missouri. The period of tree-ring record ranged in calendar years from 1671 to 2004 and fire-scar dates (n = 97) ranged from 1672 to 1980. Fire intervals for individual trees ranged from 1 to 87 years. The mean fire interval was 6.6 years for the pre-Euro-American settlement period (1672-1820), and 5.2 years for the entire record (1672-1980). A period of more frequent fire (mean fire interval = 1.6 for 1825 to 1850) coincided with Euro-American settlement of the area. The average percentage of trees scarred at the site was 16.8%, or about 1 in 7 trees sampled per fire. No significant relationship between fire years and drought conditions was found; however, events prior to 1820 may have been associated with wet to dry mode transitions

Fire History at the Southwestern Great Plains Margin, Capulin Volcano National Monument

This study documents historic fire events at Capulin Volcano National Monument over the last four centuries using dendrochronologically dated fire scars at two sites: the lower volcano lava flows (the Boca) and the adjacent canyon slopes (Morrow Ranch). The mean fire interval (MFI) was 12 years at the Boca site (before 1890) and 5.4 years (1600-1750) and 19.1 years (1751-1890) at the Morrow Ranch site. Data from the Boca and Morrow Ranch sites combined with the extremely pyrogenic landscape position of the volcano slopes indicate that the volcano slopes likely burned more frequently (e.g., MFI \u3c5 yr). Around 1750, the fire regime appeared to transition to longer fire intervals, greater temporal synchrony among fire-scarred trees, and a higher proportion of trees scarred in fire years. Temporal variability in the fire regime at Capulin Volcano may reflect changes in human populations, climate, and land use

SIX CENTURIES OF FIRE HISTORY AT DEVILS TOWER NATIONAL MONUMENT WITH COMMENTS ON REGIONWIDE TEMPERATURE INFLUENCE

This study documents over six centuries of historic fire events at Devils Tower National Monument in northeast Wyoming, USA. The 691-year tree-ring chronology is based on 37 ponderosa pine (Pinus ponderosa C. Lawson) trees collected at the monument. The period of tree-ring record ranged in calendar years from 1312 to 2002 and fire scar dates (n = 129) ranged from 1330 to 1995. The mean fire interval (MFI) for the entire record was 24.6 years, and intervals for individual trees ranged from 4 to 119 years. A period of increased fire frequency (MFI = 5.7 years) occurred from about 1860 to 1880, corresponding to the period of Euro-American exploration and settlement of the region. Comparisons of fire-climate relationships derived from Devils Tower, the Black Hills, and other Great Plains sites suggest that Devils Tower pre settlement fire events were more similar to those of grasslands. Despite this, current fire intervals and vegetation assessments suggest that conditions are departed from historical conditions. In the Great Plains, temperature appears to be a strong regional-scale determinant of fire frequency, which may become more evident considering global warming predictions

Appendix A. Supporting descriptions of methods and results.

Supporting descriptions of methods and results

Supplement 1. Radiocarbon dates, laboratories, errors in dating, and associated anatomical measurements from subfossil oaks.

<h2>File List</h2><blockquote> <p><a href="RadiocarbonAndAnatomySupplement.txt">RadiocarbonAndAnatomySupplement.txt</a> -- (MD5 checksum) 4ad6128e10fe1394a988a95d56ef9024</p> </blockquote><h2>Description</h2><blockquote> <p>The file RadiocarbonAndAnatomySupplement.txt is a tab-separated file. It contains radiocarbon dating information on sub-fossil oak samples and wood anatomical measurements from the same samples.</p> <p>Column Definitions:</p> -- TABLE: Please see in attached file. -- <p> </p> <p>Missing or blank values are numbered as “-9999”.</p> <p><i>Note</i>: Sample MED 471 does not include radiocarbon data because it was statistically cross-dated using tree-rings to another radiocarbon dated sample.</p> </blockquote