Thesis Title

A Quantitative Analysis of the Vegetation of Post Oak Savannas in Taney County, Missouri

Date of Graduation

Summer 2000

Degree

Master of Science in Biology

Department

Biology

Committee Chair

John Heywood

Subject Categories

Biology

Abstract

It is widely believed that fire suppression subsequent to European settlement of the midwestern United States is responsible for the conversion of savannas into closed woodlands. To assess the impact of past and future fire management of savannas in southwest Missouri I quantified the overstory and understory composition of an old growth savanna, a recently restored savanna, and a closed woodland that is probably degraded savanna, all located in Taney County. Canopy cover was 76% in the woodland and 41% in both the old growth savanna and the restored savanna. Mean tree size (DBH) was greatest in the old growth savanna and lowest in the closed woodland. Canopy tree diversity was the highest in the closed woodland and lowest at the old growth savanna. Total shrub cover and diversity were highest in the woodland and lowest in the old growth savanna. Herbaceous cover and diversity, however, were highest in the restored savanna, probably because it is adjacent to a diverse glade community. An herbaceous community was virtually absent from the woodland. Canopy tree boles were distributed randomly in the old growth savanna, clumped in the restored savanna, and overdispersed in the woodland; these differences probably reflect different management histories. Canopy trees were spatially clumped by species in both the woodland and restored savanna, but not the old growth savanna. All these differences between the three communities were statistically significant. The tree size distribution in the old growth savanna suggests a complete absence of recruitment during the past century, perhaps due to overmanagement or overgrazing. After a first-time prescribed burn of the woodland in the Spring of 1999, individuals smaller than 5 cm DBH suffered 66% mortality, while those over 5 cm DBH suffered only 1.2% mortality. Small, understory trees suffered the highest mortality, while the fire-resistant canopy species had lower mortalities. The results of this study suggest that long-term management of savannas may require occasional fire moratoriums to allow tree recruitment.

Copyright

© Shanda Heather King

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