Reconstructing Terrestrial Paleoclimate and Paleoecology with Fossil Leaves Using Digital Leaf Physiognomy and Leaf Mass Per Area

Our research is focused on understanding the relationship between plant traits and climate and ecology in modern plants. Then using these relationships, we can develop proxies or models that we can use to reconstruct climate and ecology in ancient plant communities. Recent research has focused on understanding the biological, physiological, evolutionary underpinnings of the relationship between plant traits and climate and ecology today and in the past.

This research has shown that plant traits respond to climate and ecology both in the lifetime of a single plant and an evolutionary time skills. Our research has demonstrated that despite the complex factors that influence plant traits, there are very strong empirical relationships between leaf traits and climate and ecology. We've used these relationships to develop models for reconstructing climate and ecology that have been applied in a variety of settings through earth history.

These methods refine the reconstruction of paleoclimate and paleoecology to provide a much more comprehensive understanding of terrestrial ecosystems and climate and is available by just studying our modern earth. Such a perspective is critical in understanding what our future earth holds as climates and ecosystems respond to anthropogenic impact. This is a leaf physionomy based approach, meaning that it does not require an accurate taxonomic identification.

In addition, DiLP uses digital measurements of continuous leaf characters as opposed to qualitative and categorical, which allows for greater reproducibility, and these leaf characters have a functional relationship to climate. To begin, position the leaf fossil under the camera and ensure it is lying as flat as possible. Photograph the fossil leaf and label the image file appropriately.

Then, open the image of a tooth leaf whose area is preserved or can be reconstructed in the image processing software and crop the image if necessary. Select image and then canvas to increase the width of the working area. Add a new canvas to either the right or left of the current canvas.

Now decide on the leaf's preparation method, determining whether to use a whole leaf or half leaf for area and shape measurements. Using a lasso tool, trace the margin of the leaf, including the petiole if present. Copy and paste the selected portion of the leaf onto an open area of the canvas, making two copies, one original, and one is a backup to revert to if necessary.

Visually follow the leaf margin to the point it contacts the petiole often darker and without distinctive veins. Place a lasso point there and repeat for the other half. Encircle the entire petiole to finish the selection.

Then, cut and paste the petiole. Copy and paste the isolated leaf with the petiole removed and place it in an open area of the canvas. Using the lasso tool, trim excess leaf material to ensure a complete half leaf remains for preparations or leave the complete leaf intact if preparing a full leaf.

Using a line or paintbrush tool, repair any damaged areas along the leaf margin with a line of appropriate color and thickness. For tooth measurements of the leaf, copy the leaf and place it in an open area on the canvas. Use the lasso tool to remove the area adjacent to damaged portions of the margin.

Begin selection at a point along the margin that bounds the damaged portion, and draw a straight line to the major vein perpendicular to it. Start the selection at the preserved primary tooth sinus closest to the damage. Continue the selection along the major vein until level with the other bound of the damaged margin.

Then draw a straight line perpendicular to the major vein to the margin. Delete the damaged portion of the leaf and repeat the process for all damaged portions. Copy and paste the version of the leaf prepared for tooth measurements and place it in an open area of the canvas.

Use a lasso tool to remove the teeth from the leaf. Start at the leaf apex, one of the lobe tips or the tip of a leaf fragment, and select each primary tooth sinus along the leaf, lobe or fragment. After selecting the apical sinus of the most basal tooth, apply the extension rule to cut the last tooth of the sequence out.

Remove the teeth by cutting and pasting them next to the leaf blade, ensuring that the removed teeth do not touch the original blade. To begin open ImageJ software and set the parameters for automatic measurements. Navigate to analyze and select set measurements.

Then select the options for area, perimeter and Feret's diameter. Now, open the prepared fossil leaf image by selecting file and open. Use the straight line tool to zoom in on the scale bar and draw the longest straight line possible across it.

To set the scale of the image, click analyze and set scale. Enter the measured length of the scale bar in centimeters and click okay. In the data entry spreadsheet, mark the leaf as 0 for tooth or 1 for entire.

Also, measure the petiole width if present, and record the data in the data entry spreadsheet. Then, select image. Type an eight bit to convert the leaf image to black and white.

Navigate to image adjust and threshold. To begin, thresholding the image. Using the slider bar, adjust the threshold until the interior of the leaf turns red and is distinctly separate from the background.

Zoom in on sections of the margin to ensure accuracy. To measure the leaf prepared for leaf area and shape measurements with the petiole removed, use the one tool and click on the interior of the leaf to outline it in yellow, ensuring the outline correctly represents the leaf shape. Make measurements using analyze and measure or using the designated keyboard shortcut and record the data in the spreadsheet.

For a half leaf analysis, select the segmented line tool in the line tool and trace the entire length of the artificial middle perimeter. Then, click analyze and measure or use the shortcut to measure the length of the artificial middle perimeter. Record area, perimeter, Feret, minimum Feret, and the length of the artificial middle perimeter.

To adjust the measurements for a half leaf in the data entry spreadsheet, multiply the area and minimum Feret by two. And calculate the blade perimeter using the given formula. Measure the area of the cutout petiole if present and record its area.

To measure the raw blade, use the one tool to select the interior of the blade outlined in yellow. Proceed with measurements by clicking analyze and measure or using the keyboard shortcut. In the data entry spreadsheet, record the raw blades area and perimeter in the designated fields.

To measure the internal raw blade, select the interior of the blade and outline the entire leaf in yellow. Make measurements by clicking analyze and measure or using the shortcut. Record the area and perimeter of the internal raw blade in the data entry spreadsheet under the respective fields.

Clear the threshold to see the leaf clearly by clicking reset in the threshold box or using edit and undo to remove modifications like the black and white conversion. Then, use the segmented line tool to trace the full length of the cut perimeter. Measure the traced perimeter by clicking analyze and measure or using the shortcut.

To count the number of primary teeth, right click the point tool first to select the multi-point tool. Click on each primary tooth to number it. To remove a point selected by mistake, press the alt key or command or CMD or option while clicking the point.

Record the final number under primary teeth in the data entry spreadsheet. Click edit, selection and select none to clear the multi-point tool counts and annotations. Then, to count the total number of teeth, right click the point tool and select the multi-point tool.

Click on each tooth, including primary and subsidiary to number it. Both McAbee H1 and H2 sides showed leaf physionomy that fits well within the calibration dataset range indicating reliability in the derived paleoclimate estimates. The reconstructed mean annual temperature and mean annual precipitation for McAbee H1 and H2 suggested a temperate seasonal biome.