Plants provide an indicator of climate because the well-being of a species is controlled by the temperature and moisture of a region, and whether those conditions suit a type of plant. That's why if you draw latitudinal or horizontal lines around the world you'll find very similar species growing along those lines, like tropical plants around the equator, or tundra and northern or boreal forest species in a circumference south of the North Pole.
From the pollen record found in sediments in Piermont Marsh of the lower Hudson Valley, a Medieval Warm period was evident from 800 to 1300 A.D. Researchers know this from the striking increases in both charcoal, a sign of dry vegetation and fires, and pollen from pine and hickory trees. Prior to this warming spell, there were more oaks, which prefer a wetter climate.
The study which appeared in a recent issue of the journal Quaternary Research is important for showing how climate in this region has changed due to natural causes prior to human interventions in the area. Dee Pederson, a researcher at Columbia University's Lamont-Doherty Earth Observatory (LDEO), Palisades, N.Y., and Dorothy Peteet, a researcher at NASA's Goddard Institute of Space Studies, New York, N. Y., and LDEO, wrote the study.
During this drought period, a core drilled into the marsh bed showed large influxes of inorganic soil particles, a sign of erosion. Plant roots hold soil in place, but with drought and pla
Contact: Rob Gutro
NASA/Goddard Space Flight Center