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Author: Andruk, Christina
Email: candruk@mail.utexas.edu
Phone: 512-471-4546
Organization: University of Texas at Austin
Address:
University of Texas at Austin Molecular Cell & Dev BIo,
Austin,
tx,
78713
Abstract Title: THE EFFECTS OF INITIAL VEGETATION COMPOSITION, SEED AVAILABILITY, FIRE AND COMPETITION ON HERBACEOUS SPECIES RECRUITMENT AND AN INVASIVE GRASS COVER IN SAVANNA RESTORATION. Christina M. Andruk* and Norma L. Fowler, University of Texas at Austin.
Abstract Text: Two invasion processes occur simultaneous in central Texas savannas: woody plants, primarily Juniperus ashei, encroach while the non-native invasive grass Bothriochloa ischaemum (King Ranch bluestem) invades open areas. Mechanical clearing can slow or reverse woody plant encroachment; however, B. ischaemum often invades in sites that have been cleared, preventing the restoration of a native-dominated open system. We examined the joint effects of initial species composition and competition reduction (through fire, clipping, or mechanical clearing) on community assembly by examining germination and establishment rates of seeds added to manipulated plots. We had plots in two sites: an old field dominated by B. ischaemum and a stand of J. ashei, part of which had recently been cleared. Seeds of 16 herbaceous native species and B. ischaemum were added to the plots. Effects on pre-existing plants: A warm-season prescribed fire was more effective than clipping in reducing cover of pre-existing B. ischaemum. Plants from added seeds had a small negative effect on B. ischaemum cover. Effects on plants from added seed: In the old field, clipping was the most beneficial treatment for forbs overall and for Ipomopsis rubra, while Gaillardia pulchella did particularly well in burned plots. Bothriochloa laguroides was favored by burning and by clipping, and B. ischaemum was relatively unaffected by treatments. B. ischaemum had a significantly higher survival rate than other grasses, suggesting a possible invasion mechanism. In the cleared woodland, fire and clearing both promoted all the herbaceous species. Clearing was more effective if woody debris was left.
Conference
Year: TIPPC_2011
Presentation Type: Oral Presentation
Presenter Type (Student or Regular):
Session: 3. Control and Management
Submission Date: 2011-09-02
