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Harvard Forest Symposium Abstract 2014

  • Title: Increasing ungulate activity promotes native plant diversity in recent patchcut harvests
  • Primary Author: Edward Faison (Highstead, Inc.)
  • Additional Authors: Stephen DeStefano (U. S. Geological Survey, Cooperative Research Unit Program, University of Massachusetts); David Foster (Harvard Forest); Glenn Motzkin (University of Massachusetts - Amherst )
  • Abstract:

    Large herbivores can either decrease plant diversity by consuming rare or less competitive plants or increase diversity by consuming competitively dominant plants, creating spatial heterogeneity through trampling and excreta, and dispersing seeds. The direction in which ungulates drive diversity often depends on site productivity, as well as the density and diets of herbivores.

    In 2013, we examined the effects of different ungulate assemblages (deer) and (moose + deer) on floral diversity and abundance in patch cut harvests 5-6 years old. We sampled 13 1-m2 quadrants in the center of 3 treatment plots (no ungulates, deer, moose + deer) in each of 6 patch cut blocks. At each of the quadrants, we recorded all herbaceous and woody plants <2 meters in height. We estimated percent aerial cover for each species and for each plant group in 1 of 7 cover classes. In addition, we performed a 20-minute “meander” survey throughout the central 13 x 13 m of each plot and recorded the presence of all plant species that did not occur in the subplots.

    Native herbaceous plant richness increased with greater ungulate activity (12.3 species; SE = 2.8 in plots with no ungulates; 13.2 species; SE = 1.6 in deer plots; 16.3 species; SE = 3.2 in moose + deer plots (F = 5.2; DF = 2; P = 0.03). Woody and total plant richness did not differ significantly among treatments. Woody species density (species m-2) also increased with increasing ungulate activity (F = 6.7; DF = 2; P = 0.01), whereas herbaceous and forb species density were similar among treatments. Woody plant cover increased sharply from no ungulates to deer to deer + moose (F = 15.4; DF = 2; P = 0.001), whereas forb, herbaceous, and graminoid cover did not differ among treatments. The increase in woody plant cover below 2 meters in height can be attributed to the dramatic height reduction of woody stems from browsing in the moose + deer plots. In general, our results from patch cut harvests are consistent with the concept that moderate ungulate activity tends to increase plant diversity in resource-rich environments.

  • Research Category: Biodiversity Studies, Conservation and Management, Large Experiments and Permanent Plot Studies