Students
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.
Mandy K. Peterson:
Status:
Current M.S. student
Thesis:
Effects of garlic mustard
(Alliaria petiolata) invasion, control, and native plant
restoration on the ecosystem services of a NE Wisconsin forest
herbaceous layer with focus on the soil invertebrate community.
Thesis Summary:
Invasive plants significantly impact the ecosystems in
which they invade by altering plant production and elemental
cycling, native plant abundance and diversity, and ecosystem food
web structure. All of these changes have direct or indirect
implications for the ecosystem services benefiting human society.
Among these, invertebrate communities appear particularly sensitive
to exotic plant invasion, with documented decreases to arthropod
biomass and diversity following invasion. A. petiolata is
known to significantly alter mycorrhizal abundance, and its biennial
life-cycle likely alters patterns on belowground production,
relative to perennial native species. Mandy will utilize a four-year
old experiment manipulating A. petiolata presence, native
plant restoration, and access by white-tailed deer (Odocoileus
virginianus) to evaluate the effects of altered plant community
composition and A. petiolata abundance on the less mobile,
and experimentally more amenable soil arthropod community. Mandy’s
research will improve our understanding of the ways by which A.
petiolata invasion, A. petiolata management, and native
plant restoration alter the ecosystem services provided by the
forest herbaceous layer.
Adam C. von Haden:
Status:
Current M.S. student
Thesis:
Carbon sequestration potential in upland and lowland row crop
and
restored tallgrass prairie ecosystems.
Thesis Summary:
Biofuels are likely to play a significant role in the impending
shift from fossil fuel to renewable energy sources. Conversion of
marginal agricultural lands to biofuel grasslands may provide
additional ecological services such as erosion control, nutrient
retention, and carbon sequestration. Adam is comparing aboveground
biomass yields, soil carbon, and fine-root production between upland
and lowland areas in crop fields and restored prairies to identify
marginal cropland and quantify nutrient retention and carbon
sequestration potential. Within the restored prairies, Adam is
examining fine-root production and decomposition along a soil
moisture gradient using root ingrowth and intact core methods,
respectively. The results of the study will provide important data
for future local carbon mitigation policy and will illustrate the
dynamics between soil moisture and net carbon flux in tallgrass
prairie soils.
Joshua A. Martinez:
Status:
Current M.S. student
Thesis:
The potential use of inter-specific facilitation
to restore native woodland herbaceous communities in urban preserves
facing strong biotic resistance.
Thesis Summary:
Josh is examining the potential use of a native
woodland grass (Elymus
virginicus) to facilitate the establishment of palatable native
woodland species. This
experiment is established within a Northeastern Wisconsin urban
preserve that carries high whitetail deer (Odocoileus virginianus) densities and extensive invasion by the
exotic biennial herb, garlic mustard (Alliaria
petiolata). Josh is quantifying local whitetail activity using
fecal group counts.
Facilitation experiments are established in 6 replicated blocks,
with E. virginicus planted
at three different densities.
Deer exclosures prevent browsing in half of all treatments plots
within each block, with seedlings from the palatable-forb target
species planted at a constant density within each facilitation plot.
Josh is also examining the differential effects of
Elymus virginicus density
on the survivorship of a suite of seeded native species and the
natural establishment of non-seeded species and garlic mustard.
Andrew LaPlant:
Status:
Undergraduate in Environmental Science
Project Title: Exotic slug abundance in five contrasting NE Wisconsin forests.
Project Summary:
Slugs occur globally, from the tropics through the temperate and boreal ecosystems, occupying a variety of habitats from grasslands to wetlands and forests. Slugs are global agricultural pests, with recent evidence that introduced slugs are also affecting plant community composition in natural areas as well. The effect of exotic herbivorous slugs in North American forested ecosystems has been overlooked, yet recent work suggests that they are having a significant effect on herbaceous community composition . Unfortunately, little information exists concerning their abundance and habitat distribution within Midwestern forests. Andrew’s research will determine the abundance of exotic slugs in five contrasting forest habitats in Northeast Wisconsin, then correlating slug abundance to plant cover, soil moisture, and soil pH. Andrew’s research will help to identify the factors shaping local slug abundance, and thus their potential influence on forest herbaceous composition among NE Wisconsin forest types.
Cody J. Sandahl:
Status:
Undergraduate in Environmental Science
Project Title:
The effects of root growth on soil microbial biomass and enzyme activity.
Project Summary:
The depletion of Midwestern soil carbon coupled with the large potential for carbon storage in those soils, suggests that biological sequestration of carbon can serve as an effective tool for stabilizing atmospheric CO2 and, in addition, restoring soil fertility. Despite its importance, we insufficiently understand how soil carbon accumulates, since root inputs themselves do not directly form soil organic matter, rather, it is a byproduct of microbial activity acting upon root inputs. This study seeks to evaluate the effects of root inputs on soil microbial biomass and enzymatic activity. Cody is comparing the microbial biomass and enzyme activity along a gradient of belowground net primary production in soil samples (0-10 cm depth) from upland and lowland areas within a restored tallgrass prairie. The results of this study will enhance our understanding of soil organic matter formation, and in practice, our ability to restore soil fertility and stabilize atmospheric CO2.
Philip G. Hahn:
Status:
M.S. May 2010
Thesis:
Drivers of native forest herbaceous layer decline:
exotic slugs more limiting to native plants than competition for an
exotic plant. - Awarded the
2010-2011 UW-Green Bay Outstanding Thesis Award
Thesis Summary:
Recently, the effects of overabundant consumers have gained
attention as a potential mechanism facilitating the dominance of
invasive plants. The
introduced slug Deroceras reticulatum is found in high
abundances in Wisconsin woodlands invaded by Alliaria petiolata
(garlic mustard) and appears to be selectively grazing on native
plants. This provided a unique opportunity to study how competition
and herbivory from introduced species interact to affect native
plant diversity. Feeding
experiments showed that the introduced slug Deroceras reticulatum
exhibited a preference for many native plants, but avoided the
invasive plant A. petiolata. Plant preference was negatively
related to leaf thickness, and rosette plants were damaged
significantly more than erect plants.
In the field, herbivory significantly reduced both the
growth and survival of seedlings from two species of native
palatable rosette plants, whereas competition from A. petiolata
had negligible affects on the growth and survival of any native
seedlings tested. In contrast, A. petiolata was not affected
by slug grazing, suggesting that consumer avoidance, not direct
competitive exclusion, is most promoting A. petiolata
dominance in our NE Wisconsin forest site.
Publications:
Hahn,
P.G., and M.E. Dornbush. Exotic consumers interact with exotic plants to mediate native plant survival in a Midwestern forest herb layer. Biological Invasions.
Accepted.
Hahn,
P.G., M.L. Draney, and M.E. Dornbush. Exotic slugs pose a previously
unrecognized threat to the herbaceous layer in a Midwestern woodland. Restoration
Ecology.
Accepted.
Simone E. Kolb:
Status:
M.S. December 2007
Thesis:
Understanding the mechanisms by which a manure-based charcoal product
interacts with soil to affect microbial biomass and activity.
Thesis Summary:
Phosphorous
loading
of freshwater systems is a serious, long-lasting, and unintentional
environmental impact than can result from livestock production.
At the same time, the offsite transport of manure needed to reduce
potential environmental impacts is often hindered by the high cost of
transporting the largely liquid waste.
Recent advances in pyrolysis technology may provide the dual benefit of
converting livestock manure into a local, renewable energy source, and an easily
transportable and agriculturally beneficial soil amendment in the form of
charcoal. To examine the potential
effects of charcoal additions to temperate soils, Simone’s thesis examines the
effect of varying charcoal application quantity on soil microbial biomass and
activity among four distinct soil series from Wisconsin, USA.
Publications:
Kolb, S.E., K.J.
Fermanich, M.E. Dornbush. 2009.
Effect of charcoal quantity on microbial biomass and activity in temperate soils. Soil Science Society of America Journal
73: 1173-1181.