Botany & Plant Ecology

Michigan Academician, Fall 2017 | Go to article overview

Botany & Plant Ecology


The Role of Generalist and Specialist Pathogens in Maintaining Forest Tree Biodiversity: A Simulation-Based Approach. Sarah E. Wilga, Michael T. Douglas, Alex J. Mercer, and Jeffrey K. Lake, Adrian College

There remain a number of questions about what maintains biodiversity in forest ecosystems. Substantial testing of competition for limiting resources, adaptation to specific local environmental conditions, and the role of herbivory have produced largely inconclusive results; these forces seem insufficient to maintain biodiversity levels observed. Increasingly, the role of pathogens has been explored as a means to explain maintenance of biodiversity, but this has been limited to specialist enemies, as described in the Janzen-Martin hypothesis. Some recent work has suggested generalist or quasi-generalist pathogens that infect phylogenetically related species may also contribute to maintenance of biodiversity. This work uses R-based computer simulations of a forest community with trees affected by generalist, specialist, and phylogenetically driven pathogens to test the impact of their interactions in a spatially explicit environment. Various analyses have considered the roles of spatial distances of tree and disease dispersal, degree of pathogen virulence, and frequency of reinfection. This work shows a number of different parameter combinations that can lead to long-term coexistence of multiple species.

Light Use Efficiency of Common and Glossy Buckthorn Compared with Two Native Shrubs. David L. Dornbos Jr. and Philip Simonton, Calvin College

Two buckthorn species, common (Rhamnus cathartica) and glossy (Rhamnus frangula), are aggressive non-native competitors in southwest Michigan. Common buckthorn (CB) predominates in sun rich environments like meadows and edges whereas glossy buckthorn (GB) is more often found in shaded, moist environments. The objective of this research was to compare the density and light use efficiency of CB and GB with two native species, gray dogwood and hawthorn, in four habitats on the Calvin College campus to determine if photosynthetic efficiency explains species distribution. The two buckthorn species had similar [P.sub.max] rates, rates that exceeded those of both native species. Glossy buckthorn was competitive in shaded and moist areas, and oddly, less so at moderate than high light intensities. While GB had as high a [P.sub.max] as CB, stomatal control mechanisms limited net photosynthesis of GB at mid-range light intensities. Hawthorn competed well with GB in all but high light environments and CB in shade. Dogwood, however, was competitive only in deep shade by virtue of low respiration rates and was otherwise uncompetitive in the environments tested. Light use efficiency explains the dominance of CB in sunny and GB in shaded habitats and their ability to displace native shrubs.

Converting Lawn to Restored Forest on a Midwest College Campus: A Seven Year Assessment of Herbaceous Plant Establishment. Leanna N. DeJong, Micah G. Warners, and David P. Warners, Calvin College

Human development has resulted in significant loss of forested areas and associated biodiversity. Thus, preserving and restoring woodland habitats is critical for recovering this biodiversity, as well as the ecosystem services it provides. While woodland restoration projects typically focus on improving degraded woodlands to more closely resemble presettlement conditions, fewer studies have attempted to understand the process of transforming highly-altered, suburban lawn-dominated landscapes back into a healthy forest ecosystem. In this study, we evaluated different strategies for establishing a temperate forest ecosystem onto land that had been maintained as suburban turfgrass. Five native herbaceous woodland plants were planted around five nurse trees in four different soil treatments. We assessed the prevalence of weeds in the various soil treatments two years after the initial planting. …

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