Impacts of Restoration and Management on Plant Communities and Belowground Processes in the Chicago Region
Umek, L. G.. 2018.
Abstract
Ecological restoration is a land management tool for biological conservation in areas where
ecosystems are subject to a suite of natural and anthropogenic disturbances. This approach is
particularly critical in urban areas where disturbances are often frequent and substantial.
Restoration projects aim to re-establish an entire ecosystem, including the native organisms as
well as the ecological processes and biotic interactions of those ecosystems for long-term
sustainability. In practice, ecological restoration has primarily focused on establishing a diverse
plant community while largely ignoring the belowground components of ecosystems.
Surprisingly little is known about the complex relationships between soil factors, plant
communities, and ecosystem processes in pristine systems, and even less is known about these
relationships in restored or urban systems. In my dissertation, I ask: how do abovegroundfocused
management practices influence plant communities and belowground processes in the
Chicago region?
I address this question using research that spans spatial and temporal scales and includes
different terrestrial habitats. I examine ecological patterns of restoration activities at sites
replicated across a large landscape, plant-soil interactions at the site level, and interactions
between plant tissues and fungal communities using molecular techniques. I also address these
questions across temporal scales. Using a restoration chronosequence, I use a space for time
substitution to investigate ecological patterns over large periods of time. In a manipulative field
study, I examine plant-soil dynamics over a period of 4 years. My study sites include private and
publicly owned lands that represent a range of upland terrestrial habitats in the Midwestern U.S.
and are managed by citizen scientists, government agencies, and professional contractors and
combinations therein. My highly replicated, regionally comprehensive, and ecologically and politically representative experimental approach ensures that conclusions from my research have
direct and immediate impacts on the understanding of these ecosystems and how they are
managed.
In Chapter 1, I describe the development of a collaborative network of protected sites that
capitalize on the shared best management practices in the Chicago region. This network links onthe-
ground restoration and land management activities with ecological research. This chapter
provides the conceptual and experimental framework as well as experimental methods for
collecting baseline data used in the subsequent studies. In Chapter 2, I describe how patterns in
plant community structure and soil nutrient levels in woodlands and prairies differ with
management duration and relate to one another. I found that in prairies, land use history is the
most important factor in determining plant community assemblage followed by more recent land
management activities. In woodlands, the initial action of removing woody invasive taxa is
critical to initiating ecosystem restoration, while on-going management maintains community
composition. In Chapter 3, I used geospatial analysis to develop a model of woodland
degradation that integrates invasive shrub density, exotic earthworm biomass, and soil nitrogen
availability. Using this model, I found that unrestored sites have significantly higher invasive
shrub cover, exotic earthworm biomass, and soil nitrogen availability than managed sites,
regardless of their time under management. I also identified notable exceptions to these patterns
that may be used to direct and prioritize future investigations and ultimately, lead to more costeffective
restoration efforts. In Chapter 4, I examine the decomposition rates of leaf litter in
remnant and former row-crop agricultural prairie ecosystems across the restoration
chronosequence and describe the functional and community composition of the decomposer fungal communities. I found that leaf chemistry was a more important driver of litter mass loss
than either land use history or management duration. I also found that although fungal
communities differed in composition, they remained functionally similar across all sites. In
Chapter 5, I conducted a manipulative field experiment exploring traditional and novel methods
of restoration following the invasion of a non-native shrub (Rhamnus cathartica). I determined
that amending soils with woody mulch following buckthorn removal significantly reduced
reinvasion over the four-year field study period but that these results are not due to a reduction in
soil nitrogen availability. Manipulative studies in the greenhouse similarly showed that mulchamended
soils significantly reduced buckthorn germination, seedling growth, and transplanted
sapling growth. The results of this study suggest that incorporation of ground woody material
into the soil following aboveground removal may facilitate restoration following European
buckthorn invasion.
In this dissertation, I set out to examine and document how aboveground-focused
management practices influence plant communities and belowground processes in the Chicago
region. My research shows that land management practices influence plant community
composition and soil nutrient availability across a range of ecosystem types. From a landscape
perspective, these results are important in that they demonstrate that local correlations between
above and belowground communities differ from those on the broader scale. From an applied
perspective, my research informs land management practice and restoration of temperate
woodlands and globally threatened tallgrass ecosystems, but also contributes to our knowledge
on the processes and interactions between plant and soil communities that determine biological
diversity in the Midwest US, especially in urban ecosystems.
