Quercus is treated as an important high temperature indicator in pollen record studies. However, the genus is difficultly identified into species level under light microscopy. California boasts more than 23 oak (Quercus) species, many of which with widespread distributions in northern and southern states. I described the ultrastructure of pollen grains of 23 modern oak species and fossil pollen from Clear Lake based on SEM images. These pollen samples were collected from trees in the University of California Botanical Garden at Berkeley and the Tilden Regional Park at Berkeley. The light microscope (LM) measurements, applied on 710 modern pollen specimens, include one size measurement, polar axis and equatorial axis, and two shape measurements, P/E ratio and p/D ratio.
Results/Conclusions
The results indicate that there are significantly difference between 5 major phylogenetic groups. In addition, three types of surface texture were recognized in the modern samples with SEM images. This study also reports analysis of oak pollen from Clear Lake samples between 85 to 140 meters depth (~81,000-235,000 yr B.P.) included pollen with the three types of surface texture.