Will fire suppression alter plant communities of the Edwards Plateau, Texas?

1. Will fire suppression alter plant communities of the Edwards Plateau, Texas? Jill M. Noel Department of Plant Biology University of Texas at Austin

2. Introduction • Context of study • What is the role of disturbance in maintaining the structure and species composition in plant communities? • What changes may occur in plant communities if disturbance frequency, intensity, or timing (e.g., season) is altered?

3. No fire SHRUB ENCROACHMENT No fire WOODLAND GRASSLANDS Fire Fire Introduction • Context of study

4. Introduction • Major questions of study: 1. What are the effects of fire on woody plant individuals and populations? 2. What are the rates and patterns of woody plant encroachment in the absence of fire?

5. Methods • Select sites with certain criteria • Scan the aerial photographs at an appropriate resolution • Use Digital Ortho Quadrangles (DOQ) as base maps • Georeference the older photographs to the DOQ • Quantify the changes in plant communities through time

6. Site Selection • Pedernales Falls State Park, Blanco County, Texas, DOQ. • Pedernales Falls was acquired by Texas Parks and Wildlife Department in 1970; opened to public in 1971. • Active fire suppression since the park became public. • Prior to the establishment of the park, the area was an active ranch, and therefore, probably not managed with fire.

7. Georeference Photos • To georeference the photos to the DOQ, a portion of a aerial photo was scanned and layered over the DOQ. • To get the best fit, a number of reference points were used. • The final fit of the photo over the DOQ can be tested visually, and by examining the table of errors. When the cummulative error is <10m, considered satisfactory.

8. Study Area • A small area of the park was burned in the winter of 1999. • This smaller area was used for this study of changes over time. • Four photos were available: 1951, 1965, 1990, and 1999.

9. 1951 1965 1999 (DOQ) 1990

10. 1951 1999

11. Future after this project • Collect similar data from at least three more sites where aerial photographs are available. • Once the changes in vegetation between time periods has been quantified, make predictions about the changes in plant community structure after long term fire suppression. • Furthermore, I would like to combine the results of this study and the previous study to make predictions about the stages at which fire may still be considered a useful management tool in maintaining plant communities.

12. Acknowledgements • C. A. Cowsert, NRCS field office, Johnson City for the generous loan of the aerial photographs of Pedernales Falls State Park. • David Maltby, Parsons Engineering Science, for help and consultation about GIS and georeferencing. • Texas Parks and Wildlife Department, for access to this and several other sites. • Dr. Maidment, for previous help with study design of this project and future help (??) with analyses of spatial associations.