Date of Award
Master of Arts (MA)
Dr. Thomas Bragg
Prescribed burning and tree-cutting were used alone and in combination to assess means by which to restore the historic Quercus savanna ecosystem that once dominated the western Iowa Loess Hills. Pre- and post-treatment evaluations of woody and herbaceous understory species, overstory canopy cover, and woody plant density were conducted in permanently established treatment plots approximately 1000-2000m2 in size. Of all plant groups, forb canopy cover increased the most, with the greatest increases occurring in pots that were burned with all trees removed (average increase from 8% to 41%), followed by burned plots with all but Quercus macrocarpa (bur oak) removed (from 4% to 26%) and then by plots that were only burned from 11% to 20%). Changes in graminoid cover paralleled forb cover by treatment with increases averaging from 8% to 34%, to 10%, and 4% to 5% respectively. Changes in understory woody species cover showed no consistent trend among or between treatments. Shannon Diversity (H’) of understory increased significantly from an average pre-treatment H’ of 2.1592, to H’ = 2.7966 for Burn-Clear, 2.5815 for Burn-Thin, and 2.5558 for Burn-Only plots. Individual species’ canopy cover either was unaffected or increased in cover was recorded for Carec spp. (sedge) (from 7% to 23%) followed by Eupatorium rugosum (white snakeroot) (from 5% to 19%), both increases occurring in burned and cleared plots at both study areas. The increase of herbaceous species, including some characteristic of prairies, provides preliminary evidence of the potential success of savanna restoration. However, the lack of a significant change in woody plant density with burning alone suggests that mechanical removal must accompany prescribed burning to restore savanna from extant woodlands.
McKenzie, David A., "Restoration of Quercus macrocarpa (bur oak) savanna in Iowa's Loess Hills." (2006). Student Work. 3355.