The ecology and integrated management of tall buttercup (Ranunculus acris L.)
Strevey, Hally Kirsten
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Tall buttercup (Ranunculus acris L.) is a perennial invasive forb found in pastures and irrigated meadows. It has been problematic in New Zealand where it excludes important forage species. The impact of tall buttercup is of interest in North America, especially in Montana where it has invaded over 8300 hectares. Minimal published research exists in the region regarding its impacts and methods of control. My research objectives were to 1) determine the associations of tall buttercup with forage, species richness, and plant diversity, 2) test integrated management strategies to control tall buttercup, and 3) assess the importance of soil moisture on seedling emergence and growth. Objective 1 was carried out in flood and sub-irrigated hayfield meadows over two years near Twin Bridges, Montana. Three transects were established along a gradient of increasing tall buttercup cover at two sites. In general, tall buttercup was found to have minimal associations. It was not associated with species richness, and was positively correlated to plant diversity. It was negatively associated with perennial grasses at one site. Objective 2 was conducted in flood and sub-irrigated hayfield meadows over two years near Twin Bridges, Montana. Treatments were applied in a split-plot design with four replications at two sites. Herbicide treatments occurred at the whole-plot level; non-sprayed, aminocyclopyrachlor + chlorsulfuron, aminopyralid and dicamba. Split-plots consisted of mowing and fertilization. All herbicides provided up to two years of tall buttercup control and mowing and fertilization controlled tall buttercup at one site. Forage production increased following aminopyralid and dicamba treatments; however, aminocyclopyrachlor + chlorsulfuron reduced perennial grasses. Objective 3 was explored in the greenhouse testing tall buttercup seedling emergence and growth along a soil moisture gradient. Seeds were planted in one of three different moisture treatments including 25, 50 and 100% field capacity. The 50% and 100% treatments had the highest seedling density, while the 50% treatment had the highest seedling biomass and height. Integrated management should be utilized for tall buttercup control, and altering irrigation practices may provide control by reducing seedling emergence and growth. Future research is warranted to understand tall buttercup invasion potential across habitat types.