Date of Award

1998

Document Type

Restricted Thesis

Terms of Use

© 1998 Susannah McCandless. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts

Department

Biology

First Advisor

Roger Latham

Abstract

The globally rare, highly diverse serpentine savanna plant community at the Nottingham serpentine barrens in southeastern Pennsylvania has diminished by 43% over the past 60 years (Latham, 1996). Rigorous fire suppression is the most likely cause of the transition to low-diversity Pinus rigida and Quercus woodlands, with the thorny lianas Smilax rotundifolia and S. glauca forming dense, monogeneric undergrowth. This study examined aspects of Smilax's role in the serpentine barrens ecosystem: its influence on soil biogeochemistry and its rooting patterns. Serpentine soil syndrome is often thought to be based on low calcium/magnesium ratios, and high soil nickel levels. The data reported here, however, suggest that Smilax ameliorates serpentine soil conditions primarily by nitrogen enrichment. At the Smilax-dominated ecotone, high relative N content of Smilax leaves is reflected in significantly higher relative N content of underlying organic soil horizons. In contrast, Smilax did not show an effect on organic soil Ca/Mg ratios, and Ni levels in organic soil appeared to be parent material- rather than plant- driven. Smilax rhizomes were found primarily in upper, combustible soil horizons. This suggests a management strategy for restoring savanna recently lost to Smilax encroachment, since high severity burns could kill Smilax while strongly promoting the regeneration of serpentine savanna species. Smilax's physiological ecology suggests that it may be promoting an alternative steady state on the Nottingham serpentine barrens.

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