"As readers of this Blog know well, overabundant white-tailed deer populations have serious negative effects on understory plant community structure and composition(biodiversity)"............... "Wolves, which are top predators of deer, have been recolonizing central Wisconsin since the early 1990s. "Two different research studies( U.S. Forest Service-2006, State U. of NY/U. of Wisconsin-2013) have come in with similar findings---Results suggest that seedling survival of preferred, browse- sensitive seedlings is higher in areas continuously occupied by wolf packs(Wolves as top down carnivores enrich biodiversity of surroundings)".............."These results are consistent with hypothesized trophic effects on understorey plant communities triggered by a keystone predator(Wolves) recovering from regional extinction"............. "These studies represent the first published evidence of a trophic cascade triggered by wolf recovery in the Great Lakes region"

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&cad=rja&uact=8&ved=0ahUKEwiByMPM8q_YAhXS31QKHXnJAfwQFgg_MAQ&url=https%3A%2F%2Fwolvesofdouglascountywisconsin.com%2F2016%2F10%2F07%2Fgray-wolves-in-northern-wisconsin-are-saving-the-forest%2F&usg=AOvVaw3j7mL7-pW8pP_pRKsHOEAw

Wolf Recovery and the Future of Wisconsin's Forests: A Trophic Link

12/15/16; 

• US Forest Service Research & Development
• 1400 Independence Ave., SW
• Washington, D.C. 20250-0003
• 800-832-1355

Principal Investigators(s) :
Moser, W. Keith
Research Location : Wisconsin
Research Station : Northern Research Station (NRS)
Year : 2010
Highlight ID : 208

Snapshot : Overabundant white-tailed deer populations have serious negative effects on understory plant community structure and composition. Wolves, which are top predators of deer, have been recolonizing central Wisconsin since the early 1990s. NRS scientist Keith Moser and partners from the University of Georgia are measuring trophic cascade effects, that is, whether wolves are reducing local browse intensity by white-tailed deer and thus mitigating the biotic impoverishment of understory plant communities.

HIGH WOLF DENSITY ZONES IN THE NICOLET NATIONAL FOREST
REVEAL HIGHER DENSITY OF OAK AND RED MAPLE SEEDLINGS
THAN IN LOW DENSITY WOLF ZONES

 Top picture high density understory in hi Wolf density zone
and bottom picture reveals low density understory in low 
Wolf densisty zone

 THE TROPHIC CASCADES, " TOP-DOWN" POSITIVE
INFLUENCE OF WOLVES ON THE ENVIRONMENT

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=15&cad=rja&uact=8&ved=0ahUKEwiqnIvq86_YAhVqwlQKHcnYDv04ChAWCDgwBA&url=http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1111%2F1365-2745.12095%2Ffull&usg=AOvVaw2WtbH3R8U3S-cQjve0eP3j

Recolonizing wolves trigger a trophic cascade in Wisconsin (USA)-June 6, 2013

Authors

Photo pair of understorey vegetation within the Chequamegon-Nicolet National Forest, WI. (Top) Shows a high wolf area (within the Bootjack Lake pack territory) and (bottom) shows the paired low wolf area (in the buffer zone between the Bootjack Lake pack and the Miles Lake pack).

Summary

1. We tested the hypothesis that wolves are reducing local browse intensity by white-tailed deer, thus indirectly mitigating the biotic impoverishment of understorey plant communities in northern Wisconsin.
2. To assess the potential for such a top-down trophic cascade response, we developed a spatially and temporally explicit model of wolf territory occupancy based on three decades of wolf monitoring data. Using a nested multiscale vegetation survey protocol, we compared the understorey plant communities of northern white cedar wetlands found in high wolf areas with control sites found in low wolf areas.
3. We fit species–area curves for plant species grouped by vegetation growth form (based on their predicted response to release from herbivory, i.e. tree, seedling, shrub, forb, grass, sedge or fern) and duration of wolf territory occupancy.
4. As predicted for a trophic cascade response, forb species richness at local scales (10 m2) was significantly higher in high wolf areas (high wolf areas: 10.7 ± 0.9, N = 16, low wolf areas: 7.5 ± 0.9, N = 16, P < 0.001), as was shrub species richness (high wolf areas: 4.4 ± 0.4, N = 16, low wolf areas: 3.2 ± 0.5, N = 16, P < 0.001). Also as predicted, percentage cover of ferns was lower in high wolf areas (high wolf areas: 6.2 ± 2.1, N = 16, low wolf areas: 11.6 ± 5.3, N = 16, P < 0.05).
5. Beta richness was similar between high and low wolf areas, supporting earlier assumptions that deer herbivory impacts plant species richness primarily at local scales. Sampling at multiple spatial scales revealed that changes in species richness were not consistent across scales nor among vegetation growth forms: forbs showed a stronger response at finer scales (1–100 m2), while shrubs showed a response across relatively broader scales (10–1000 m2).
6. Synthesis. Our results are consistent with hypothesized trophic effects on understorey plant communities triggered by a keystone predator recovering from regional extinction. In addition, we identified the response variables and spatial scales appropriate for detecting such differences in plant species composition. This study represents the first published evidence of a trophic cascade triggered by wolf recovery in the Great Lakes region.