Conversion of exotic cool-season grasslands to restored native plant communities utilizing herbicide treatments.

摘要

Exotic, invasive weeds are a major issue in maintaining, rehabilitating, and restoring native plant communities. Many areas in the northern Great Plains are now dominated by exotic cool-season grasses such as smooth brome (Bromus inermis), Kentucky bluegrass ( Poa pratensis), and reed canarygrass (Phalaris arundinacea ). Information was collected to evaluate methods of control for exotic grass species and reestablishment or rehabilitation of native plant communities in eastern South Dakota.;During the fall of 2005 and the spring of 2006, I implemented a smooth brome removal study at five reed canarygrass sites in eastern South Dakota. Five fall herbicide treatments, two spring herbicide treatments, and an untreated control that received no herbicide or seed addition were applied at each location in fall 2005-spring 2006 and fall 2006-spring 2007. Three fall herbicide treatments and two spring herbicide treatments were added for fall 2006-spring 2007. Herbicides were applied over clipped vegetation that had residual vegetation removed in 2005-2006 and over standing vegetation in 2006- 2007. Sites were seeded with a native plant mix within two weeks following spring herbicide treatment. Reed canarygrass cover in untreated plots ranged from 80-99%, while cover on herbicide treated plots ranged from 0-98% on 2005-2006 plots and 26-99% on 2006-2007 plots at the conclusion of the study, suggesting that clipping is necessary to achieve adequate control. Native plant response was limited throughout the study.;During the fall of 2005 and spring of 2006, I implemented a smooth brome removal study at five smooth brome sites in eastern South Dakota. Seven fall herbicide treatments, five spring herbicide treatments, an untreated plot that was planted with a native seed mix, and an untreated control that received no herbicide or seed addition were applied at each location in fall 2005-spring 2006 and fall 2006-spring 2007. Based upon first year results, three fall herbicide treatments and two spring herbicide treatments were added for fall 2006-spring 2007. Sites were seeded with a native plant mix within two weeks following spring herbicide treatment. Smooth brome cover in untreated plots ranged from 73-99%, while cover on herbicide treated plots ranged from 0-84% on 2005- 2006 plots and 0-98% on 2006-2007 plots at the conclusion of the study. Future response of native plants will be important in determining the proper timing and herbicide combination.;During the fall of 2005 and spring of 2006, I implemented a removal study at six native prairie sites in eastern South Dakota that had been invaded by smooth brome and Kentucky bluegrass. Treatments included five herbicide combinations, a fall burn, and an untreated control. Untreated plots averaged 64% smooth brome cover and 38% Kentucky bluegrass cover after the third growing season. Smooth brome and Kentucky bluegrass cover on herbicide treated plots ranged from 6 to 23% and 15 to 35%, respectively, after the third growing season. Burned plots had 20% and 19% cover of smooth brome and Kentucky bluegrass, respectively, after the third growing season. Spring and fall treatments had similar native plant cover after three growing seasons.;I initiated a study at two sites in southeastern South Dakota to determine the necessary rates of JourneyRTM herbicide applied pre-emergence to establish native grasses. Spring application of 0.07 kg ai/ha imazapic + 0.18 kg ai/ha glyphosate, 0.09 kg ai/ha imazapic + 0.25 kg ai/ha glyphosate, and 0.11 kg ai/ha imazapic + 0.31 kg ai/ha glyphosate and an untreated control were applied at each site. Plots were seeded within two weeks following herbicide application with a mixture of native warm- and cool-season grasses. My results indicate that a pre-emergent application of 0.07 kg ai/ha imazapic + 0.18 kg ai/ha glyphosate can improve establishment of planted native grasses.;Vegetative characteristics and grassland bird use of conservation plantings were studied in eastern South Dakota Game Production Areas, June 2007-2008. Fourteen fields, from one to eight years old at the onset of the study, were surveyed in each year to describe vegetative characteristics and to correlate grassland bird use. Grassland birds were sampled along fixed width transects during June 2007-2008. Vegetation was sampled at seven points along three parallel transects within the bird sampling transects. Younger plantings had lower height and cover dead vegetation, greater litter depth, higher coverage of alfalfa and unplanted forbs, and more bare ground than older plantings. Nonmetric multi-dimensional scaling based upon vegetative characteristics showed that sites tended to become more similar with age. Fifteen bird species were identified during transects in each year. Six species showed a relationship between abundance and the measured vegetation structure and composition variables.