Date of Graduation

8-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Environmental Dynamics (PhD)

Degree Level

Graduate

Department

Environmental Dynamics

Advisor/Mentor

Stephenson, Steven L.

Committee Member

Boss, Stephen K.

Second Committee Member

Cleaveland, Malcolm K.

Third Committee Member

Dixon, John C.

Fourth Committee Member

Tullis, Jason A.

Keywords

Biological sciences; Health and environmental sciences; Allelopathy; Carbon sequestration; Eucalyptus; Introduced species; Kenya; Mycorrhizal fungi

Abstract

Eucalyptus trees were introduced to Kenya a little over a century ago. European colonization along with the development of a railway system increased the demand for a fast growing wood source. The expansion of the tree across the fertile lands in Kenya raises concerns about the environmental impact on ecosystems where it has been introduced. These concerns include degraded soils, loss of water resources, co-introduction of ectomycorrhizal species, and allelopathy. Economic benefits to local landowners were also explored as well as the potential for large Eucalyptus woodlots to maximize the sequestration of CO₂ from the atmosphere. This was examined through farmer interviews and the collection of data from both Eucalyptus and indigenous forests. The results indicate that the density of Eucalyptus varied by age and species and managed harvest rates could be utilized to maximize carbon content in Eucalyptus to increase carbon sequestration potential of woodlots. In the greenhouse study of allelopathy, Eucalyptus did inhibit the growth and germination of the test plants. The indigenous plants were the most strongly affected. The soil analyses indicate that overall, Eucalyptus may not have a strong effect on the soils but do have a significant effect on soil moisture and diversity found within the woodlots. Ectomycorrhizal fungi were molecularly identified as some of the same species associating with Eucalyptus in Australia, indicating co-introduction. Farmers indicated that they were aware of the environmental concerns associated with cultivating Eucalyptus but the economic benefits were greater than the environmental issues.

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