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Madritch Research

My research focuses on linking population and community processes with ecosystem functions. I am interested in how global changes - such as reductions in biodiversity, shifts in atmospheric chemistry, and spread of invasive species - influence critical ecosystem services.

Genes to ecosystems: Genetic variation and ecosystem functioning
NSF DEB DEB-0104804, DEB-0344019
This research program integrates two major themes - the ecosystem consequences of both intraspecific genetic variation and herbivory - through the shared common denominator of plant chemical composition. We have demonstrated that the genetic composition of temperate forests can have large implications for nutrient release during leaf litter decomposition, and that plant genotype can interact with nutrient availability to influence belowground processes.  In addition to the direct effects of leaf litter decomposition, plant genotypes can also have indirect genetic effects by mediating the ecosystem responses of canopy herbivores. We are currently investigating how herbivory and nutrient availability affect plant nutrient uptake and decomposition using mesocosm experiments that employ stable isotopes to track the specific fates of plant- and herbivore-derived nitrogen.

 

Remote sensing of forest genetic diversity and assessment of belowground microbial communities in Populus tremuloides forests
NASA Biodiversity 08-BIODIV-7
Our genes to ecosystems work demonstrates that aspen genotypes can create spatial mosaics of genetically-mediated ecosystem functioning across natural landscapes. This landscape level work has lead to a NASA-funded remote sensing project that involves collaborators at the University of Wisconsin and Utah State University.  We are using remote sensing techniques to quantify forest genetic diversity and resulting belowground microbial diversity.  Understanding the causes and implications of global declines in biodiversity is at the forefront of ecological research. To date, however, remote sensing techniques have yet to be applied to their full potential to address the genetic component of biodiversity.  Combining large-scale remote sensing data with fine-scale genetic data will greatly increase our understanding of biological diversity across natural landscapes.

Plant chemistry and belowground processes
Many belowground processes are driven by the quality and quantity of aboveground inputs. Although secondary metabolites are best known for their herbivore and pathogen defense roles in living leaves, they also have several important impacts on terrestrial nutrient cycling.  Several of my projects address the specific afterlife effects of leaf litter quality on belowground processes. 

Soil Warming
Soils account for the majority of carbon storage in terrestrial ecosystems and soil temperatures are expected to rise as the result of continuing climate change. However, relatively little is known regarding the consequences of soil warming to microbially-mediated belowground nutrient cycling. Instead of using traditional, artificial soil warming techniques we employ reciprocal soil transplants along locally available elevation gradients. The size of our transplanted soil cores allows us to measure both soil and plant nutrient cycling responses.

Belowground effects of invasive species
Invasive species can have severe and long-lasting effects on ecosystems and native communities. We are looking at how multiple invasive plant species influence belowground processes, and how these effects may change with climate and geographic range. We have developed black locust (Robinia pseudoacacia) as a model system because if its symbiotic relationship with nitrogen fixing Rhizobium and because it is a severe invader in parts of the midwestern U.S. and Eurasia where it occurs outside of its native Appalachian range.

Cliff face ecology
Cliff face ecosystems are chronically understudied and are potentially rich reservoirs of genetic diversity. In addition, cliff ecosystems are increasingly facing pressures from multiple users and land managers often lack basic biological information to make informed decisions. Working with Gary Walker, my lab collaborates with National Park ecologists to better understand and predict plant distributions on cliff faces. My lab also focuses on nutrient cycling in cliff systems to determine the relationships between nutrient availability and species abundance.