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UBC Theses and Dissertations

Influence of kin, density, soil inoculum potential and interspecific competition on interior Douglas-fir (Pseudotsuga menziesii var. glauca) performance and adaptive traits Asay, Amanda Karlene


Positive interactions between plants, in addition to competition, can help shape a plant community and ecosystem. Positive interactions can come in the shape of intraspecific interactions such as kin selection, or interspecific interactions, such a mycorrhizal symbiosis. Previous studies have provided evidence for both of these processes occurring in interior Douglas-fir (Pseudotsuga menziesii var. glauca) with the possibility that they are linked. This thesis focuses on potential influences on the processes of kin recognition and selection including density, soil (mycorrhizal) inoculum potential and species-specific community composition. In three studies regarding kin relationships of year-old seedlings, evidence supporting kin recognition via differences in morphological traits and kin selection via differences in performance between kin and stranger seedlings was provided. We found that increasing the plant density created environments where kin seedlings behaved in a more similar manner to strangers when seedlings were grown in pots with limited resources. Decreasing the soil inoculum potential, while decreasing overall performance, increased the kin response. When grown in the field, seedlings required a greater density for a kin/stranger differential response to be detected. By changing community composition at a consistent density, we observed cooperative behaviours in kin seedlings grown with only other kin and unique responses when kin and strangers were grown together in a group suggesting integration of multiple cues. Our results could have important forest management implications, particularly surrounding the concepts of legacy trees and natural regeneration of the locally adapted seed they produce, maintaining access to mycorrhizal associations and networks and the potential for family substructuring. Kin relationship considerations may be particularly important in harsh climates or at the leading edge of the range of Douglas-fir, which is expected to move northward and upward as the climate shifts.

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