Recent palynology of the Cedar Mesa area, Utah

Gerald James West

A major problem in attempts to reconstruct vegetation and sequences of climatic change from pollen samples derived from archaeological deposits is the effect of human activity in the vicinity of the site on vegetation, and hence on the pollen rain. This problem is examined in the Cedar Mesa area of southeast Utah, region sporadicallyoccupied by Anasazi horticulturalists 700 to 1800 years ago.Pollen spectra obtained from modern soils, sediments and archaeological deposits of the region provide evidence of vegetation change in the past. Three models to explain the change in the pollen spectra and various methods to correct for possible anthropogenic disturbance representedin the pollen spectra from archaeological deposits proposed by previous investigators are examined in light of the Cedar Mesa data. The modern pollen rain of the Cedar Mesa area is a reflection of the modern-day vegetation. Differential anthesis of various species accounts for most of the seasonalvariation noted in the pollen spectra over a 4 year period. The relationship of the ratio of pine to juniper pollen (P/J) as a function of elevation was found to be not as strong as the tree ratio to elevation, but P/J averages based on plant communities suggest a stronger relationship. Absolute abundance of pollen appears to be a function of elevation in the Cedar Mesa area, butin areas of disturbed vegetation the absolute abundance of pollen varies independently of elevation.Pollen grains derived from chenopods and amaranths are relatively and in some cases absolutely most abundant in disturbed areas. The pollen of these two genera dispersesignificantly differently than arboreal pollen in that their distribution is more localized. Therefore, when interpreting pollen spectra derived from archaeologicaldeposits, they are not reliable as indicators of regional changes in the environment which might be expected to occur as the result of climatic change. An abundance of chenopod and amaranth seeds derived from archaeological contexts on Cedar Mesa and other nearby areas suggestsa heavy reliance on these genera for subsistance, further emphasizing the point that the utilization of their variation in the pollen record as regional environmentalindicators is questionable. By analyzing P/J pollen ratios and double-fixed pollen sums from archaeologically derived pollen data, itis suggested that the climate and potential vegetation of the region was not significantly different from today's.The pollen evidence does not suggest secular changes in the bi-seasonal rainfall pattern as suggested by earlier workers in the southwest.It is further inferred that the pollen profiles derived from archaeological deposits represent forest successionfollowing disturbance and abandonment by prehistoric Anasazi populations. It is quite probable that the Anasazi had a significant impact on their environment and may have upset the delicate balance between vegetation, soil mantle and runoff. Note: Completed at the University of California, Davis, this dissertation deals with the Cedar Mesa archaeological site in the southwestern United States.

Recent palynology of the Cedar Mesa area, Utah

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