I am interested in the landscape patterns and community mechanisms that influence the addition of species into ecosystems. I employ multi-scale techniques, where I determine landscape-level influences on nonnative species demography and further investigate these influential factors with patch-scale community manipulations and analyses. My interest in landscape preservation is served by utilizing a variety of methods to answer pressing questions relating to the addition and loss of species in ecosystems. My research interests span four related themes:

  1. The investigation of ecosystem and anthropogenic factors that influence invasion by nonnative species
  2. Characterization of the impacts, interactions, and the type of species to invade natural areas,
  3. Understanding changes in ecosystem function as a result of ecological restoration, and
  4. Economic impacts and policy implications of nonnative species invasions.

The investigation of ecosystem and anthropogenic factors that influence invasion by nonnative species

Hemlock bordering Big Stony Creek, Jefferson National Forest, VA I have investigated ecosystem factors that contribute to high levels of invasion across the landscape as well as community-level interactions between nonnative species and native residents and how these interactions change across stress levels. I am especially interested in investigating legacies of land use history on habitat invasibility.

The 'biotic resistance' hypothesis has been an extremely popular explanation for variable levels of invasion across natural habitats. However, there may be multiple explanations for why nonnative species occur in some habitats and not others. Environmental factors are important determinants of habitat invasibility and may change biological influences on invasion, depending on the system invaded. For example, native residents may compete with invaders in benign habitats and facilitate invaders in stressful and disturbed habitats.

Related publications

Characterization of the impacts, interactions, and the type of species to invade natural areas

Surveying former locust stands, Cape Cod, MA A current and expanding area of my research is investigating facilitations between non-native species. In a field study conducted in 2003 with my summer research students, we established that the introduced N-fixing tree, Robinia pseudoacacia, had an average of ten times the number and cover of nonnative species under its canopy, compared to native-canopied forest (primarily Pinus rigida and Quercus alba/velutina) located 20 m from the sampled locust stand. Total land cover of Robinia pseudoacacia, or black locust, in the outer Cape has significantly declined over the past three decades. However, preliminary soil analyses have revealed that nitrogen cycling is significantly higher under locust than under native forest. The areas that were formerly locust stands (as revealed by aerial photography and field identification) are intermediate between native pine-oak and nonnative locust stands in levels of ammonium, nitrate and nonnative species richness. Competition and soil nutrient experiments in the field and greenhouse are in progress to understand the mechanism for the understory dominance of locust stands by nonnative species.

Related publications

Understanding changes in ecosystem function as a result of ecological restoration
Heathland habitat, Martha’s Vineyard, MA

A natural counterpoint to the identification and control of nonnative species is the restoration of degraded habitats. I am interested in the restoration of ecosystem function of formerly cultivated land and am collaborating with Chris Neill, of the Ecosystems Center of the Marine Biological Laboratories, on a large-scale heathland restoration experiment on Martha's Vineyard, MA, where the overall project goal is to determine the most appropriate method of restoring heathland habitat to this system in order to optimize rare plant diversity, resistance to invasion by nonnatives, and restoration of natural rates of nutrient cycling. We are currently looking for motivated graduate students to collaborate with us on this research project in collaboration with the Nature Conservancy of Martha's Vineyard.

Summer 2005 field team weeding the restoration plots, Cape Cod, MA To explore how biotic resistance of native communities to nonnative invasion changes with increasing atmospheric deposition, I have initiated a restoration experiment comprised of nutrient additions and the addition of varying numbers of native heathland species into old field plots. The native richness experimental treatments were established in the summer of 2004; half of these plots were amended with nutrients (twice the level of atmospheric deposition) and all were 'invaded' with nonnative plants in the summer of 2005. Thus, with the combination of landscape-level observations and community-level experiments, I am examining the interaction between anthropogenic disturbance with native diversity in determining community addition by nonnative plant species.

Economic impacts and policy implications of nonnative species invasions

Currently, the United States spends $120 billion a year in total direct costs for non-indigenous species. This estimate is total direct costs of nonnative species control and eradication, yet there are many indirect costs associated with the invasion of nonnative species, such as loss of aesthetic appeal and native biodiversity. Invasive Plants in Protected Areas workshop, Corbett National Park, India I would like to collaborate with economists in quantifying the direct and indirect costs of a nonnative species for a given region or species. Harmful nonnative species continue to invade the US, from both intentional and unintentional routes. There is a powerful need for new and inventive policies to address this issue that is so costly for our environment and economy. I collaborate with researchers and policymakers to address these needs and spur more creative thinking and action for this pressing conservation concern.

Related publications