The tallgrass prairies of the Great Plains are declining and have suffered a loss of at least 90%, due to agricultural conversion. Many restored prairies are managed with the use of a disturbance regime. Because prairie disturbances remove or damage all or part of the aboveground biomass of the plants, the timing of the disturbance in combination with plant phenology and growth form affects the overall impact of the disturbance. We tested how the interactive effects of timing of disturbance (haying in May, July, and September) and functional group (C3 grasses, C4grasses, early flowering forbs, and late flowering forbs) impacted aboveground biomass production and affected plant community composition in the early years of restoration in a 0.8ha field experiment near Vermillion, SD. We measured plant community composition in 2014 and 2015 and aboveground biomass in 2015. We used a two-way ANOVA to test how the time of haying and functional group affected hayed biomass and total annual aboveground biomass and will use ordination to determine how plant community composition varied among treatments and between years.
Results/Conclusions
We found that the month of haying significantly impacted productivity for the hayed biomass (F(2,33)=20.43, p<0.001) and the total annual aboveground biomass (F(2,33)=13.60, p<0.001). Functional groups did not have a significant effect on hayed biomass (F(3,33)=1.43, p=0.25) or total annual aboveground biomass (F(3,33)=2.05, p=0.13). Preliminary results for the plant community composition demonstrate a transition from primarily annual agriculture weeds, especially Chenopodium album (lamb’s quarter), in 2014 to a significant proportion of tallgrass prairie species, especially Elymus canadensis (Canada wildrye), in 2015. Our results are consistent with those of other studies indicating a shift from annual agricultural weed species to prairie species in the second year after prairie seeding. Our results differ from other studies, however, in that functional group did not have a significant effect on aboveground biomass production but the month of haying did. Longer-term evaluation of the plant community composition and aboveground biomass production will enable us to more fully understand the impact that repeated disturbances have on the plant community.