Mathew E. Dornbush
Ph.D. Iowa State University 2005

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.