Paleo Slide Set: Packrat Middens: Vegetation & Climate Variability in the Southwestern United States
Bristlecone pine needles from late glacial age packrat midden; Ladder Cave in eastern Nevada.

The macrofossils found in this late glacial midden from Ladder Cave in eastern Nevada provide evidence 
for the low elevation occurrence of what are now high elevation plants. This difference in elevation 
range indicates that the mean annual temperatures of Ladder Cave during the last glacial period were 
possibly as much as 10C below modern temperatures. In most cases the excellent preservation of biological
remains from packrat middens permits identification to the species level as demonstrated by the bristlecone 
pine (Pinus longaeva) needles shown in this slide. This is the same pine that produces 7,000-year-old living 
individuals and climate-sensitive tree-ring chronologies in the White Mountains of eastern California and 
western Nevada. 

Photo Credits:
Robert S. Thompson & Robert S. Webb 
U. S. Geological Survey & NOAA National Geophysical Data Center