|Jordan, Nicholas - UNIVERSITY OF MINNESOTA|
|Svenson, Elizabeth - UNIVERSITY OF MINNESOTA|
Submitted to: Agriculture Ecosystems and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2005
Publication Date: May 20, 2005
Citation: Blumenthal, D.M., Jordan, N.R., Svenson, E.L. 2005. Effects of prairie restoration on weed invasion. Agriculture Ecosystems and the Environment 107:221-230. Interpretive Summary: Restored tallgrass prairie may be more competitive with weeds than is vegetation typically planted in non-cropland (e.g. roadsides and old-fields) within agricultural landscapes. We tested this hypothesis by adding weeds to restored prairie and vegetation similar to that typically planted in non-cropland. Relative to no-restoration, restoration reduced added weed biomass by 93% in year one and 76% in year two, and reduced biomass of 4 individual weed species, each by greater than 92%. Restoration also decreased the size of individual weed plants and reduced light, suggesting that restored prairie reduced weed invasion through competition. Furthermore, adding nitrogen to the soil reduced the effect of restoration on some weeds, suggesting that competition for nitrogen may have mediated the effect of prairie on weeds. Restoration may also have inhibited weeds by decreasing weed germination and establishment, a hypothesis suggested by the thicker layer of dead plant material and smaller number of individual weed plants in restored prairie. Also in accord with this hypothesis is that burning, which removed dead plant material, reduced the effect of restoration on some weed species.
Technical Abstract: Weed control in non-cropland often precludes management for biological diversity. It may be possible, however, to use native late-successional plant communities to exclude weeds, thereby managing simultaneously for diversity and weed control. We tested whether restored tallgrass prairie excludes early-successional weeds. To separate the effects of late successional prairie vegetation from factors that commonly co-vary with late successional vegetation (propagule pressure and time since disturbance), we added seed of 12 weed species to randomized, 6-year-old plots of restored prairie and unrestored, old field vegetation. Restoration reduced added weed biomass by 93% in year one and 76% in year two, and reduced biomass of 4 individual weed species, each by greater than 92%. To examine mechanisms underlying weed responses, we treated subplots with burning (to reduce establishment limitation), and N addition (to reduce competition). That restoration decreased weed invasion by increasing the strength of competition was suggested by increased biomass of extant vegetation, decreased light levels, decreased weed size with restoration, and by amelioration of restoration effects on weeds with N addition. That restoration decreased weed invasion via establishment limitation was suggested by increased litter mass and decreased weed density with restoration, and by amelioration of restoration effects on weeds with burning.