Long-term regional shifts in plant community composition are largely explained by local deer impact experiments.
Level 5 - mechanism / opinion, no new human data
Non-human ecological field study combining exclosure experiments with historical observational resurveys.
PubMed 25551827 · doi:10.1371/journal.pone.0115843
What was done
Researchers measured plant species responses to white-tailed deer presence using 10- to 20-year-old deer exclosure experiments across four sites in the upper Midwest, USA. They analyzed the abundance, height, reproduction, and functional groups of common species inside versus outside exclosures. They then correlated these experimental local herbivory effects with data tracking 50-year regional shifts in plant species abundances across 62 sites.
What was found
Among common plant species, 8 were more abundant outside exclosures (exposed to deer), 7 were more abundant inside, and 16 had similar abundances. Deer herbivory doubled exotic plant abundance and increased ferns and graminoids, while decreasing tree regeneration, forb abundance, plant height, plant reproduction, and shrub cover (by 100- to 200-fold in two species). Zero of 36 focal species grew taller or reproduced more in the presence of deer. When compared to long-term regional data across 62 sites, deer herbivory effects accounted for substantial variation in 50-year species abundance shifts (R² = 0.41).
Why it matters
This study links medium-term local experimental exclosures directly to multi-decade regional shifts, showing that white-tailed deer browsing is a primary driver of long-term understory composition changes in Midwestern forests.
Limits
The experimental exclosure data came from only four sites. While 41% of regional variance was explained, 59% remained unexplained by deer herbivory alone, leaving room for other drivers such as climate, canopy changes, or land-use history. Specific deer population densities and exact species-level statistics were not fully detailed in the abstract.
Cited by
- supports High deer population densities cause significant ecological damage to woodlands in the Midwestern United States.