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theses

The hard maple group is comprised of several taxonomically ambiguous, phenotypically plastic, and genetically variable taxa, native (mainly) to the United States. Northern Sugar Maple, Acer saccharum Marsh, the most recognizable group member, is culturally, ecologically, and economically important in that region. Southern hard maples have adapted to climates defined by increasing thermal loading and extended periods of drought. Understanding southern hard maple behavioral response is needed in planning future efforts on developing strategies to sustain the role of northeastern sugar maple. I provide brief overview of hard maple taxonomy, silviculture, and relevant studies. I then describe a greenhouse study in which I compare the quantified mechanical drought response of hard maple populations from range extremes. I found differential drought response to be higher among northern trees than southern trees. Southern hard maples modified stomatal aperture earlier than did northern trees, and water use efficiency was highly correlated with provenance of study groups. Next, I describe a study to better understand environmental boundaries of southern hard maples, where I quantify processes associated with plant biochemistry to determine differential drought response among southern hard maples exposed to extreme neglect during a summer heat wave. Southern trees did not exhibit significant differentiation in biochemical study parameters among taxa, but population means were influenced by time, suggesting a tight genetic link to seasonality in the southern cohort. I also undertook a genotyping analysis of hard maple germplasm tissue that I collected from field campaigns and the drought studies to determine the correlation between drought response and genotype among taxa. Relative genetic variance was highest for individuals within provenances, followed by variance among taxa, with provenances within taxa showing the least variation. All populations were shown to be significantly different genetically. Groupings resulting from population pairwise comparisons from the drought study (Tukey’s HSD) were compared to those for the genotype AMOVA (ΦPT). Groupings were not consistent between the drought study and the genotype analysis. These results suggest that in terms of breeding and selection programs for improving sugar maple industry stock, it is important to consider provenance location as an important indicator of plant performance. Genetic affinity is only part of the story.

ETD_10838

Ph.D.

Includes bibliographical references

doi:10.7282/t3-k42z-pf53

ETD doctoral

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