PARENT SESSION
Oral Session #10: Paleoecology. Presiding: S. Hotchkiss.
Monday, August 6, 2001. 8:00 AM to 12:00 PM. Hall of Ideas J.

Holocene dynamics of forest and barrens on a sand plain in Upper Peninsula, Michigan.

Lytle, David¹, ¹

ABSTRACT- Clearcutting and fire in 1895 A.D. destroyed the white pine forest of the Kingston Plain, a sand plain in Upper Peninsula, Michigan. Low water availability, likely caused by losses of forest canopy and soil organic matter, has prevented significant reforestation for the last century. The unforested barrens vegetation on the plain today is clearly anthropogenic in origin. However, because the effects of logging and fire are similar to those of catastrophic blowdown followed by fire, it is possible that both barrens and forest are natural vegetation types on the Kingston Plain. Using fossil pollen from the sediments of small ponds, I am investigating whether the Kingston Plain was unforested at other times during the Holocene. Following the 1895 disturbances, pollen records show non-arboreal pollen (NAP) percentages more than doubled, while arboreal pollen (AP) influx decreased by 40%. Only two other periods, 9200-8900 years before present (ybp) and 7900-7350 ybp, show signs of barrens vegetation. In these periods NAP percentages were not as high as in modern samples, and it is unclear whether the plain was as open as the modern landscape. These results show that although forest vegetation has dominated the plain during the Holocene, barrens vegetation, once established, can persist for several centuries. Disturbances that substantially disrupt the feedbacks between forest vegetation and water availability are likely critical for the creation and persistence of barrens.

KEY WORDS: disturbance, forest, barrens, pollen