PARENT SESSION
Oral Session #62: Vegetation change: Succession, recovery, facilitation. Presiding: S. Franklin.
Thursday, August 9, 2001. 8:00 AM to 12:00 PM. Hall of Ideas G.

Recovery dynamics in tallgrass prairie following the removal of an invasive shrub (Cornus drummondii).

Lett, Michelle¹, Knapp, Alan¹, ¹

ABSTRACT- The invasion of grasslands by woody species is a worldwide phenomenon often associated with fire suppression. Without fire, shrubs form "islands" of woody vegetation within the grassland matrix, excluding most herbaceous species typical of tallgrass prairie. We removed fourteen islands dominated by the shrub Cornus drummondii to assess the recovery dynamics of grassland species and processes. Community recovery was assessed by comparing species composition, cover, and ecophysiological responses among shrub removal sites, intact shrub islands, and undisturbed prairie. Photosynthesis in Andropogon gerardii was 54% higher in removal sites compared to intact shrub islands and 45% higher compared to undisturbed prairie. This response was presumably due to increased resource availability, as PFD and available N were increased in removal sites relative to intact shrub islands and undisturbed prairie. Total cover in shrub removal sites (37%) was significantly lower than in undisturbed prairie (216%) the first year after removal, but was not significantly different from total cover (exclusive of C. drummondii) in intact shrub islands (50%). Cover by forbs, grass, and perennials followed the same pattern. Proportional cover of forbs and annuals, however, tended to be higher in removal sites than in undisturbed prairie. We conclude that, despite increased resource availability after shrub removal and the prevalence of undisturbed prairie adjacent to removal sites, reestablishment of tallgrass vegetation structure and function will require several growing seasons in sites formerly dominated by shrubs.

KEY WORDS: Cornus drummondii, shrub invasion, succession, tallgrass prairie