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Lara Souza

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Research Interests

My research focuses on investigating the role of dominant species structuring communities and the role of biotic and abiotic factors associated to processes and patterns of plant invasions. I conduct my research across multiple spatial scales as I believe that spatial extent greatly influences the process and patterns in ecology.
My research takes place in old-field ecosystems where I ask questions regarding community structure and invasibility. My dissertation has been a combination of observations where I document the biotic and abiotic factors associated with native and exotic species richness, as well as experiments testing for biotic and abiotic factors regulating the invasion on a rank one invasive species.

Current & Past Projects

Biotic and Abiotic Factors regulating the Establishment and Distribution of an invasive plant species at Multiple Spatial Scales
Lespedeza cuneata is considered to be a rank one invasive species in Tennessee, as well as in other U.S. states.  Lespedeza was first introduced in the late 1800s for wildlife forage and is currently introduced for erosion control. Once established in natural communities, Lespedeza can form dense stands displacing native flora. Although some studies have addressed the effects of Lespedeza in plant communities in its introduced range, no studies have investigated the effects of the resident community on the initial invasion of this plant species.
Here I ask two main questions: 1) What is the role of biotic and abiotic factors on Lespedeza establishment and persistence in local old-field communities? 2) What are the biotic and abiotic factors associated with Lespedeza abundance across the landscape?

Dominant species effects on community structure, ecosystem processes and invasibility
Dominant species can structure communities and affect their subsequent invasibility. Recently, invasion ecologists have focused on the role of dominant species on biotic resistance in plant communities.  I specifically asked two questions: 1) What is the role of dominant species on subdominant community structure and 2) How do dominant species affect old-field community invasibility by Lespedeza cuneata?
Two plant genera: Solidago (species S. altissima) and Verbesina (species V. occidentalis & V. virginica) make up 40 % of total aboveground biomass across old-field communities.  The potential effects of these two taxa on structuring communities and affecting invasion in old-fields can be significant as they likely utilize a substantial amount of resources.  In this study, I removed Solidago & Verbesina from an old-field community for two years and then added Lespedeza seeds and quantified emergence and survival over one growing season.

Patterns of Native and Exotic Richness Across Spatial Scales in Old-Field Communities
The biotic resistance hypothesis posits that native species diversity will decrease the susceptibility of communities to invasions. Greater native diversity is suggested to represent greater resource utilization and lower resource availability for colonization by exotic species.  Although great support to this hypothesis has been provided at small spatial scales, at larger spatial scales, communities with greater native diversity are also less resistant to invasions. 
In this project, I asked two main questions: 1) What is the relationship between native and exotic species richness across spatial scales and 2) What factors drive the relationship between native and exotic species richness?

Selected Publications

  • Crutsinger GM, Souza L, Sanders NJ.  (2008) Intraspecific diversity and dominant genotypes resist plant invasions. Ecology Letters. 11: 16-23.
  • Garten CT, Classen AT, Norby RJ, Brice DJ, Weltzin JF, Souza L.  (in press)  Role of N2-fixation in constructed old-field communities under different regimes of [CO2], temperature, and water availability. Ecosystems
  • Souza L, Sanders NJ, Weltzin JF.  (in review) Differential effects of dominant species on community structure and invasibility. Oikos
Lara Souza

Contact Information

Lara Souza
Ph.D. Student
Department of Ecology & Evolutionary Biology
569 Dabney Hall
University of Tennessee
Knoxville, TN 37996-1610

Phone: (865) 974-3065
Fax: (865) 974-3067
Email: lsouza@utk.edu