Paul Hartzog

Candidate for Doctorate Degree
Doctoral Program in Plant Biology and Conservation 
Northwestern University
and Chicago Botanic Garden

Research Interests: Wetland biogeochemistry, denitrification, restoration, invasive species, nutrient dynamics, natural abundance stable isotopes

Current Research


Walking down the path to a sedge meadow along a stream fed by a natural spring

Out in a beautiful sedge meadow

Denitrification Enzyme Activity Assay

I am quantifying the effects of plant-community change and restoration on denitrification in wetlands. Denitrification is the bacterial conversion of biologically available nitrogen to gaseous forms and is an important process because it could reduce excess nitrogen availability caused by anthropogenic nitrogen inputs.

Replacement of native plant species by invasive plant species is a major threat to wetlands. Wetland ecosystem services may be impacted by plant-community changes associated with invasion. In southern Wisconsin, the invasive Phalaris arundinacea L. (reed canarygrass) often replaces the native Carex stricta Lam. (tussock sedge). Losses of plant diversity and microtopographic heterogeneity associated with P. arundinacea invasion may impact denitrification. The USDA’s Wetland Reserve Program, a program that converts marginal farmland back to wetland, typifies restorations in this region. These restorations are often heavily invaded by P. arundinacea and their ability to perform ecosystem services like denitrification is not well known.

In addition to investigating the links between invasion, restoration and denitrification, I am also investigating the use of natural abundance stable isotopes to measure wetland denitrification. The most common method for measuring denitrification is the Denitrification Enzyme Activity Assay (DEA), which measures ex situ denitrification potential. Development of a natural abundance isotope method could provide more accurate measurements of denitrification by measuring in situ values.



Grants, Honors and Awards


Initiative for Sustainability and Energy at Northwestern Student Grant

Society of Wetland Science North Central Chapter Student Research Grant


Northwestern Plant Biology and Conservation Travel Award


Northwestern Plant Biology and Conservation Award for PhD Students

Nominated for a Weinberg College Outstanding Graduate Student Teacher Award

Recipient of a Teagle Fellowship, a program that worked with graduate TAs to discover ways to improve teaching at the university level


May 8, 2013