Populations

Three main factors caused changes in North American plant communities over the last 20,000 years, including: 1) warming temperatures and glacial retreat, 2) Native Americans, and 3) the appearance of Europeans and their animals. Based on evidence, seed production, germination, and seedling recruitment was not a problem prior to European settlement in North America.

• The structure of relic bigtooth maple populations were compared to adjacent J. ashei populations.
• The overstory, understory density, and basal area was determined for both communities using the quadrat procedure.
• There were no bigtooth overstory or understory plants in the hilltop mountain cedar or Juniperus communities.
• Bigtooth maple had an inverse quadratic size distribution with few juveniles.
• There was little or no recruitment of bigtooth maple in the previous 20 years.
• Mountain cedar had many understory plants and considerable recruitment.
• One bigtooth maple established in the 1670s, two in the 1760s, and most in the 1970s.
• Causes of the lack of recruitment could be episodic due to changes in herbivory, management, or other environmental conditions.