Characterizing and comparing bud bank in native and invaded mixed-grass prairie in the Northern Great Plains
A serious problem facing land managers of many prairie remnants of the Northern Great Plains (NGP) is the invasion and persistence of exotic plants. Many such invasive plants in the NGP are mainly dominated by vegetatively reproducing perennial grasses and forbs, whose population dynamics are strongly driven by belowground bud banks. Plant communities with high invasive species bud banks may be more persistent and harder to restore, whereas plant communities with high native species bud banks should be less vulnerable to invasion and more stable. This research will characterize and compare belowground bud banks on plant communities dominated by native species vs. prairie vegetation that has been invaded by exotic species.
Soil cores were taken from native prairies dominated by native species and from grasslands dominated by Bromus inermis and Poa pratensis in northeastern South Dakota during early spring, mid-summer and late fall. Underground plant structures were washed free of soil and examined under a dissecting microscope to determine the bud density for each functional group. Bud density dynamics for each functional group and total number of buds were compared between native grassland and Bromus inermis and Poa pratensisinvaded grassland.
No significant difference of bud density for total and each function group were found among all sampling dates within each vegetation type. Native forbs, introduced forbs, and shrub bud density made up less than 2 and 1% of total bud density in native and infested vegetation, respectively.
Bud density in native vegetation was dominated by native graminoid axillary buds and was significantly higher than infested vegetation; but no significant difference was found in native graminoid rhizome buds between the two vegetation types.
Bud density in infested vegetation was co-dominated by introduced gramionid axillary and rhizome buds and both were significant higher compared to native vegetation.
Minimum native bud density in native vegetation was 4,500 buds/m2, whereas the maximum native bud density in infested vegetation was 2,500 buds/m2, which may indicate that a threshold of belowground native bud density may exist between 2,500 and 4,500 buds/m2.
Results suggest that graminoids dominate belowground bud banks in the ecoregion. Introduced graminoids may have a competitive advantage by producing equal numbers of phalanx tillers for local persistence and guerilla tillers for expansion, whereas native graminoids primarily produce axillary buds.