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This report presents the results of a four-year study on techniques for revegetation of native sedges in created basins. Although often the dominant genus in shallow wetlands, sedges (Carex spp.) do not readily recolonize after restoration or creation of the water table. It is unlikely that sedges will naturally establish in created wetlands. The results of seed germination studies on five Carex species suggest the highest germination rates in fresh seeds - with one exception. Wet/cold storage also can prolong seed viability for at least two-and-a-half years. Dry storage is not recommended for wetland sedge seeds. Short-term wet/cold treatment after prolonged dry storage does not improve germination rates. Sensitive to deep water, rising water levels, and competition during the establishment year, seedlings grew well across a wide range of water depths in subsequent growing seasons. Both species outcompeted annual weeds within two to three growing seasons, but not Phalaris arundinacea (reed canary grass). The study recommends weed control during the establishment year to prevent the invasion of P. arundinacea. Wetland soil promotes seedling growth relative to other soils, but does not affect germination rates. Because of the potential for the introduction of undesirable weeds, the study does not recommend the use of donor wetland soil. Instead, study results suggest the potential for the use of organic top-dressings.

Our project addresses two critical needs: to update existing MnDOT turfgrass recommendation lists and to develop a new process to keep lists continually updated in a fair manner with data-driven recommendations. We evaluated the current list of MnDOT-approved turfgrass varieties and found underperforming varieties that should be removed. We then found new, improved varieties that should be considered for inclusion on the MnDOT lists. To facilitate a process to keep lists updated for the future, we first conducted a survey of seed distributors. Using their input, we developed a new process that MnDOT can use to approve turfgrass varieties for inclusion as official seed mixtures. Ultimately, this will lead to a more nimble, consistent, and clear process so that existing and new seed vendors can have complete confidence in data-driven decision making by MnDOT.

This Technical Summary pertains to Report 2023-20, “Turfgrass Seed Variety Evaluation Process,” published June 2023.

This project sought to examine whether it was possible to re-introduce naturally occurring soil fungi called vesicular arbuscular (VA) mycorrhizae back into disturbed soils as part of a normal seeding operation for restoring a prairie. The project consisted of three phases; 1) a survey to determine the types of VA mycorrhizae occurring in different soils and vegetation types (i.e. general roadside, prairie remnant, prairie planting); 2) collect from the wild and then grow prairie VA mycorrhizae species in a greenhouse at the University of Minnesota; 3) install the VA mycorrhizae along with seed from a conventional native seed drill and monitor whether the cultured VA mycorrhizae formed mycotrophic associations with prairie species in the field. This project was a preliminary feasibility study and was not intended to answer long term questions regarding the possible benefits VA mycorrhizae may confer to roadside plantings or other prairie restorations. All phases of the project were successful. The survey indicated that differences in VA mycorrhizae composition exist between different sites. It is possible to produce VA mycorrhizae in a greenhouse by culturing on living plant hosts. The VA mycorrhizae produced was successfully installed along with seed into field plots and did form mycotrophic associations with newly planted prairie species. Preliminary results obtained from this project indicate that further investigation is warranted.

A study was performed to assess the use of perennial native grasses in the control of leafy spurge and Canada thistle and also to evaluate the effects of herbicides applied during the fall to leafy spurge crown buds. As part of an integrated vegetation management program, grass treatments containing the native prairie grass little bluestem established well and were effective at reducing the cover of leafy spurge. Paramount to the success of using native grass species is getting adequate grass establishment which necessitates the careful selection of grass species adapted to the specific site conditions. A fall application of the herbicide picloram at 0.5 and 1.0 lb ai/acre was very effective at controlling leafy spurge and may be mediated via the direct absorption of picloram by the elongated crown buds at this time. The report contains an extensive literature review of the biology and weed control efforts of both leafy spurge and Canada thistle.

This report presents the results from a study on shear stress partitioning for vegetation. The project involved partitioning the shear stress from overland flow into one component that acts on the vegetation (form shear) and the remainder that acts on the intervening soil particles (particle shear). Particle shear is important for predicting soil erosion. The study used idealized shapes to represent vegetal elements. Researchers designed and constructed a unique laboratory hydraulic flume, which they used in conjunction with hot-film anemometry to measure particle shear. They also designed and constructed instrumentation to measure the form shear on individual rigid vegetal elements, taking detailed spatial and temporal shear stress measurements for three element densities. Form shear was measured on each element within the test array. The study investigated a total of 16 test scenarios. Particle shear accounted for 13 to 89 percent of the total shear. Shear partitioning theories developed for wind erosion adequately represent the observed data and can be used to determine an appropriate vegetation density for a threshold particle shear.

The project involved intense monitoring of two permanent plots of spring-fen vegetation at the St. Croix Watershed Research Station, Washington County, Minnesota, during the growing seasons of 1994-1999. Plot C was covered by a thin layer of mineral sediment, deposited during the heavy rains of summer 1993. At each plot, the research measured the peat surface, water-table elevations, hydraulic heads, cover by open water, and litter cover. Researchers analyzed water samples for pH, specific conductance, and absorbance, took samples for diatom analysis, and conducted vascular-plant surveys during each survey. The bryophyte flora was surveyed in 1991 and again in 1994 and 1999. The vegetation cover was photographed seasonally and initially included stereographic air photos as baseline images. Very little unidirectional change can be observed on plot C. Comparisons of the recorded changes between the plots and among the results of the seasonal surveys suggest that only the seasonal amplitude of variation on plot C might have increased. After summer 1996 relative water tables and piezometer heads drop on both plots. The hydrological measurements suggest that both plots have become significantly drier, but the vegetation appears not to have responded yet, nor has the peat build-up stopped.

Maintaining roadsides for safety and aesthetics is an important issue for all levels of government throughout Minnesota. Vegetation is one important element of roadside maintenance. This handbook provides guidelines for effective management of roadside vegetation for local agencies, and highlights seven best management practices that were identified through research, surveys, and discussion with industry experts. The seven best management practices for roadside vegetation fall into these seven categories: 1. Develop an integrated roadside vegetation management plan; 2. Develop a public relations plan; 3. Develop a mowing policy and improved procedures; 4. Establish sustainable vegetation; 5. Control noxious weeds; 6. Manage living snow fences; 7. Use integrated construction and maintenance practices. The main conclusion from the handbook is that successful roadside vegetation management depends on an integrated approach. This includes a wide variety of best management practices to address the many issues involved. This integrated approach includes an assessment of the existing conditions and determination of the type of roadside environment desired. Other construction operations, including proper seeding techniques, selection of the correct plant in the right area, selection of salt-tolerant seed species where needed, and erosion control, will greatly affect the roadside condition. Use of integrated construction and maintenance practices is one of the most important best management practices identified in the handbook. An updated version is available in report 2008-20.

The primary goals of this project are to discover management processes that benefit a restored prairie and reduce the need for prescribed burning. Moreover, because of the interdependence of the plants and soil, there is a strong focus on the soil community as a driving force of the vegetation. Consequently, our objectives were to assess the effects of manipulation (burning, mowing) on: (1) the vegetative community, (2) the belowground mycorrhizal fungal community, and (3) on soil parameters. Prescribed burning has the strongest effects on plant community composition and is the most effective method to increase aboveground plant biomass in a restored tallgrass prairie. Burning especially favors warm season grasses (WSG) and legume species, though it also favors certain annual species. Spring haying is an acceptable alternative to spring burning, though its effects are less dramatic than the burn. In particular, haying does not favor WSG as extensively and may not damage cool-season species as thoroughly as burning. Adding lime to hayed prairie may help benefit the cool-season plants, native and exotic. However, utilizing mowing instead of burning probably does not differ much from leaving the prairie untreated. The process of removing litter seems to be the most important cause of the ecosystem response to prescribed burning. Hayed plots are the most similar to burned plots in terms of soil moisture, temperature, and litter quantity. Hence, litter removal by haying will likely be a sufficient practice to replace prescribed burning at many sites.

This research project examined mycorrhizal and plant factors involved in roadside reclamatin. The addition of fertilizer did not benefit native prairie plantings and generally is not recommended for use at roadside prairie restoration sites.