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Harvard Forest Symposium Abstract 2018

  • Title: Grasses, Grazers, and Conservation – An Exploration of the Effects of Conservation Management Practices on Plant Diversity and Invasion Dynamics
  • Primary Author: Martha Hoopes (Mount Holyoke College)
  • Additional Authors: Jerilyn Jean Calaor (University of Guam); Brittany Cavazos (Rice University); Dan Flynn (Arnold Arboretum of Harvard University); Anna Mayrand (Emory University); Alina Smithe (Mount Holyoke College)
  • Abstract:

    Although woodlands cover much of the terrestrial, natural lands in New England, grasslands present a significantly different system in a forested mosaic landscape with different conservation management and different invasion dynamics. Woody species tend to encroach and shift these habitats toward woodlands, but grassland systems in New England offer habitat for an increasingly rare set of plants, vertebrates, and invertebrates. Conservation managers employ a range of mowing, burning, and grazing approaches to maintain grassland systems, but these approaches all have economic, energy, and invasion consequences. At Harvard Farm we are comparing the effects of quick rotation grazing, constant grazing, and haying on native plant species and the spread of invasive species by monitoring plant communities in 27 long term monitoring plots. Baseline censuses were conducted in 2014, and grazing treatments were applied in the summers of 2015, 2016, and 2017. We re-censused all plots in early summer and after grazing treatments in 2015 and 2016 and grassy plots in 2017. In all treatments, existing woody shrub patches have continued to have the highest species diversity, and former golf course greens have altered the most as they shift from very depauperate communities to a wider array of species. Overall, mowing appears to lead to less homogenization than grazing, but results are still preliminary and are confounded by some inconsistency in the application of treatments (i.e., escapee cows). All grassland plots are increasing in species richness, including increases in native, non-native, and invasive species, but plots in the constant grazing treatment appear to be increasing diversity fastest. We expect that the distinct effects of the treatments will become clearer and more interpretable in future years.
    In 2017 we also explored the effects of non-native, non-invasive Trifolium spp (T. pretense and T. repens), which increase nitrogen availability, and Rumex acetosella, which is invasive in Massachusetts. Field surveys of ten 1x1m plots with and without each species revealed no community effects of these non-native species, but greenhouse studies suggested that R. acetosella has strong negative effects on plant growth and that Trifolium litter facilitates the growth of R. acetosella. We plan to explore these results further by increasing our replication in our field observations and examining the effects of R. acetosella and Trifolium on the growth of several native and non-native grassland species.

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