Current Research Projects

I am an active member of the Environmental Science & Policy Graduate Program at the University of Wisconsin - Green Bay. We offer M.S. degrees with emphases in Ecosystem Studies, Resource Management, and Environmental Policy & Administration. If you are interested in pursuing a M.S. degree under my direction, please contact me directly.

Interacting forces drive garlic mustard invasion and dominance in Wisconsin woodlands

M. Dornbush (UW-GB) and M. Draney (UW-GB)

Introduction:

This experiment at the Bay Beach Wildlife Sanctuary, Green Bay, WI is designed to investigate the mechanisms by which Alliaria petiolata (garlic mustard), invades and subsequently maintains dominance within NE Wisconsin forests. Land management organizations currently spend millions of dollars per year on the control and management of invasive plant species in the United States. However, without a clear understanding of the how and why that invasive species succeed, this money may be used inefficiently and ineffectively. For example, should invasive species simply be a symptom of larger environmental problems, money spent on direct control of invasive species may never actually address the true problem, and thus serve grossly ineffective. To address this issue, in this collaborative project we are evaluating how multiple factors may interact to promote A. petiolata success. Our objective is to determine if and how native plant communities can be successfully returned to A. petiolata invaded forests. In this experiment we are directly testing the effect of active restoration of the native flora, of eliminating one widespread ecosystem stressor (in this case browsing), and the effect of the direct removal of A. petiolata on community restoration.

Experimental Design:

Fully replicated, 3 factor split-block design:
4 Blocks
Deer exclosures (present (hatched) or abscent (open))
Garlic mustard (removed (-GM) or intact (+GM))
Native Plant Restoration (restored (+R) or unrestored (-R))

Dimensions:
Blocks: 10-m wide by 17-m long
Plots: 3 m-by-3 m
Control boarders: 1 m wide

A restored plot within the deer exclosure, but with garlic mustard not removal.

Hypotheses:

H1: Potential recovery of native plant communities is strongly limited by the availability of native plants and propagules.
H2: Over-browsing by herbivores more strongly limits native plant recovery than direct competition with A. petiolata.

Sub-project: effects of forest restoration on litter invertebrates

M. Draney (UW-GB) and M. Dornbush (UW-GB)

Introduction:

As a sub-project within the main restoration experiment, we have been monitoring the ground-layer invertebrate assemblages of these plots over time to document how the restoration treatments affect the diversity and structure of invertebrates, which constitute an important part of the ecosystem.

The main sampling method is pitfall trapping; one trap is placed at the center of each 3 x 3 meter plot. Traps operate continuously during two week periods in early summer (late June/early July) and autumn (late September/early October) of each year. They trap invertebrates moving across the ground surface, including slugs, isopods, millipedes, centipedes, spiders, harvestmen, and insects of all sorts. By counting and identifying the catch, we can begin to gain some picture of the structure of the invertebrate community (the total assemblage of interacting species) in each plot.

Hypotheses:

1) Differences between the treatments will increase over time (as the plots undergo different successional trajectories in response to the treatments), and

2) Treatments that increase plant diversity will also increase invertebrate diversity.

It is possible that higher invertebrate diversity may actually promote higher plant diversity (mediated through seed dispersal, pollination, changes in herbivore and predator diversity or abundance, etc.), and not just respond to it. Additional work is needed to document such processes. Early data suggest that slugs (Arion and Deroceras spp.) are important herbivores which may affect plant community composition differently depending on our restoration treatments, and we currently have one M.S. student pursuing this question.

A pitfall trap at the restoration plots. The green fluid is propylene glycol, which preserves the invertebrates that fall into the cup. Rain is kept out via a plywood roof suspended by nails, and chicken wire keeps curious mammals out of the traps.

Root niche partitioning facilitates the maintenance of local richness in tallgrass prairie

M. Dornbush (UW-GB) and B. Wilsey (Iowa State University)

Introduction:

This project seeks to understand factors promoting the high local plant richness typical of tallgrass prairie, by examining the importance of root-partitioning of soil depth as a means of promoting or prolonging coexistence among tallgrass prairie species. This project is founded upon the contradictory patterns reported from observational studies of decreasing plant richness with increasing soil depth, and the very high local richness reported from fertile, deep soil prairies of the Midwest. There is also considerable existing evidence for interspecific differences in plant rooting depth, and foraging strategies, but few direct evaluations of the importance of these differences for shaping plant community composition and for affecting ecosystem processes.

Experimental Design:

2 Blocks (established in central Iowa in 2003, or in 2004)
3 depth treatments: 20-cm shallow soil, 42-cm medium soil, >1-m deep soil
Plots are 0.17 m² (n = 15 in 2003, n = 12 in 2004)
All plots were seeded with 36 native species, then hand weeded.

Hypotheses:

H1: We predict that deep soil will support a more species rich flora than shallower pots, resulting from a greater degree of root niche partitioning within deeper soils.
H2: We predict that species loss with decreasing soil volume will result primarily from the loss of less abundant forbs, with little to no change to the dominant grasses.