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Harvard Forest REU Symposium Abstract 2017

  • Title: Effects of nitrogen fixers on grassland plant communities
  • Author: Jerilyn Jean M Calaor (University of Guam)
  • Abstract:

    With the abandonment of heavy agriculture in New England, reforestation threatens the unique habitat grasslands provide. Strategies for decreasing woody incursion remove biomass and may create a battleground for native and nonnative species. This study explores, observationally and experimentally, whether nitrogen fixers, like Trifolium, facilitate nonnative plants with negative effects on native species. At Harvard Farm, within a long-term study to assess the effects of cow grazing and mowing on plant communities, we surveyed plant species richness and cover in paired 1x1m plots with and without Trifolium. We found higher Shannon-Wiener diversity in Trifolium plots, but there were no significant effects on species richness except the addition of Trifolium itself. Percent cover of nonnatives decreased in the presence of Trifolium, but Trifolium appeared to have no significant effect on native species cover or richness. In the greenhouse, we explored the effects of soil type and plant litter by growing Rumex acetosella, an invasive plant, and Oxalis stricta, a native wildflower, in three soil types (potting, Rumex, or field soil) with four litter treatments (no litter, Trifolium, Rumex or general leaf litter). Growth of both species was highest in potting soil and lowest in Rumex soil. As for the effects of litter, growth was highest with no litter and lowest with Rumex litter. Trifolium litter had a positive effect on Rumex and a negative effect on Oxalis when compared to leaf litter. Unlike the field results, the greenhouse results suggest Trifolium may facilitate invasive species and have negative effects on natives.

  • Research Category: Invasive Plants, Pests & Pathogens; Conservation and Management; Biodiversity Studies