Spearman’s rank order correlations between modern stand and leaf litter data.

<p>Spearman’s rank order correlations between modern stand and leaf litter data.</p

<i>Acer rubrum</i> (Red Maple).

<p>(A) Coarse, compound serrated margin of subfossil EMS 419504. (B) Middle portion of a lobe, subfossil EMS 419505. (C) Lobe apex, subfossil EMS 419503. (D) <i>Acer rubrum</i> reference image from sample M9-1 of the Allegheny National Forest, Pennsylvania collection <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079317#pone.0079317-Mann1" target="_blank">[76]</a>. Numbers correspond to the probable areas of a lobe represented by EMS 419504, EMS 419505, and EMS 419503. Arrows in (A–C) point to dichotomizing tertiary veins near the margins. (E) Epifluorescence image showing puberulent vein junctions with aduncate trichomes and stomatal configuration on EMS 419505.</p

<i>Betula lenta</i> (Sweet Birch).

<p>(A) Whole subfossil EMS 419583, showing doubly serrated margin. Arrows point to compound agrophic veins. (B) EMS 419582, showing acute apex and doubly serrated margin. Also note the insect damage on (A) and (B). (C) EMS 419581, exhibiting a doubly serrated margin and an acuminate apex. (D) Whole subfossil EMS 419583, showing cordate base, doubly serrated margin, and compound agrophic veins (arrows). (E) EMS 419581, cuticular and stomatal configuration. Epifluorescence image. Inset image is a closeup of subulate trichomes from EMS 419578. (F) Axillary trichomes from EMS 419583. Subulate trichomes also evident on primary and secondary veins (arrows). Epifluorescence image.</p

Denlingers Mill leaf mat site (arrow).

<p>(A) Limestone and phyllite bedrock and quartz gravel composing channel bed. (B) Darker hydric soil layer containing plant macrofossils. (C) Approximately 4 m of silty legacy sediment. (D) Exposed bedrock supporting a contemporary riparian forest. Arrow points to exposure from which all subfossils for this study were collected. Each scale bar unit = 1 m. See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079317#pone-0079317-g003" target="_blank">Figure 3</a>.</p

<i>Acer spicatum</i> (Mountain Maple).

<p>(A) Whole subfossil EMS 419502. (B) EMS 419502, axillary tufts of acicular, aduncate, and filiform trichomes. Epifluorescence image. (C) Dense acicular, aduncate, and filiform basal trichomes of sample EMS 419502. Epifluorescence image. (D) and (E) <i>Acer spicatum</i> reference image from sample M5-2 of the Allegheny National Forest, Pennsylvania collection <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079317#pone.0079317-Hardin1" target="_blank">[72]</a>. Epifluorescence images. (D) Image shows axillary tufts with the same types and configuration of trichomes as (B), while (E) exhibits the same dense basal trichomes seen in (C).</p

<i>Platanus occidentalis</i> (American Sycamore).

<p>(A) Arrows point to characteristic multiradiate (tall and branched) trichomes in vein junctions of subfossil EMS 419506. Epifluorescence image. (B) Whole subfossil EMS 419506, showing a bristle-tipped lobe. (C) Close-up of preserved multiradiate trichome in vein junction from image (A).</p

<i>Quercus</i> section <i>Lobatae</i> morphotypes (Red Oak subgroup).

<p>(A) EMS419516. (B) EMS419524, juvenile. (C) EMS419523, section of what was a very large leaf with preserved secondary veins, but no preserved midvein. Arrows point to preserved acute, bristle-tipped lobes. (D–F) Examples of cuticle variation among specimens. Inset in middle image shows distinctive T-shaped guard cell junctions; inset scale bar = 30 microns. Epifluorescence images.</p

<i>Salix</i> sp. (Willow).

<p>(A) Characteristic salicoid tooth from left margin (as viewed) of whole subfossil. Epifluorescence image. (B) Complete specimen EMS 419501. (C) Well-defined salicoid tooth from right margin (as viewed) of subfossil, also showing well preserved stomata. Epifluorescence image.</p

Radiocarbon ages of leaf macrofossils from Denlingers Mill.

<p><i>Footnotes</i>: In uncalibrated years BP & calibrated calendar years AD; analytical uncertainties of calibrated ages ±2 sigma. Calibrated ages obtained using CalPal 2007 online radiocarbon calibration package <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079317#pone.0079317-Danzeglocke1" target="_blank">[69]</a> available: <a href="http://www.calpal-online.de/" target="_blank">http://www.calpal-online.de/</a>. Samples were analyzed for accelerator mass spectrometry (AMS) radiocarbon dating at the Center for Applied Isotope Studies, University of Georgia.</p

Stratigraphic profile of the Denlingers Mill leaf mat site.

<p>Green blocks indicate the presence of dense leaf mat layers within the hydric soil unit. Subfossil leaves in this study were taken from all leaf mat layers. Yellow triangles indicate locations of samples taken for ¹⁴C dating. The X at the top of the section represents the covered interval. See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079317#pone-0079317-g002" target="_blank">Figure 2</a>.</p