Poster: Global Change

Abs # 67: Responses to elevated carbon dioxide by a regenerating pine ecosystem

Presenter:	Campbell, William J., campbell@latech.edu
Authors	Campbell, William J. (A)   Osuna, Miguel A. (A)   Vavrek, Milan C. (A)
Affiliations:	(A): Louisiana Tech University

To determine the impact of elevated atmospheric carbon dioxide on regeneration of a pine ecosystem following tree harvest, experiments were conducted in 24 open-top chambers. Chambers were 1m by 2m in height, and were constructed of clear greenhouse film over a PVC frame. Forest soil from a clear-cut site was transferred into the chambers, 12 of which were maintained at 360 ppm and 12 at 760 ppm carbon dioxide. In addition to seeds naturally present in the forest soil, seedlings of 5 different species were transplanted into the chambers. After 18 months plants were harvested, dried, and weighed. Analysis of individual plants of 8 non-graminoid species indicated differential significant responses in dry weight of total plants, flowers, roots, and the proportion of total plant weight comprised of roots. There was no significant response in shoot weight. Data from species for which individual plants could not be separated (primarily graminoids) indicated a difference in response to carbon dioxide concentration only in the proportion of the total plant weight comprised of roots. Across all species and treatments there was a significant increase in productivity in plots with chambers compared to control plots without chambers. Whereas no overall effect of elevated carbon dioxide was detected on productivity, differential species responses do suggest that species composition and competitive relationships will change in future regenerating pine ecosystems.