Models of Growth and Mortality Following Long-term Translocation of Wild Ash Populatinos
Open Access
- Author:
- Berkebile, Jennifer L
- Graduate Program:
- Ecology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- May 15, 2015
- Committee Members:
- Kim C Steiner, Thesis Advisor/Co-Advisor
- Keywords:
- Linear mixed-effects model
provenance test
green ash
white ash
Fraxinus americana
Fraxinus pennsylvanica - Abstract:
- Climate change predictions have implications for long-lived, slow-growing, sessile organisms such as forest trees. Past research indicates that trees are fairly well adapted to local environments in which their wild ancestors evolved. Given the large and climatically diverse “natural” (putatively pre-Columbian) ranges occupied by many American species, it is logical to suppose that tree species may have intraspecifically variable responses to future climate change. I have used data from two provenance tests, one of green ash (Fraxinus pennsylvanica Marsh.) and one of white ash (Fraxinus americana L.), to model the responses to climate change of green and white ash and 55 and 50, respectively, natural populations within each. Using a mixed-effects modeling framework, I have developed models of 32- to 39-year survival and mean annual diameter growth as functions of climatic distance, or the difference between the climate of the plantation site and the climate of the population autochthony. Three models have peaks in survival or growth at small negative or positive climatic distances, possibly indicating that most populations are reasonably well adapted or have a small lag in local adaptation. White ash growth, however, is highest at a large, negative climatic distance, which possibly reveals limitations in the data used in the models. For both species, the random effect of plantation has a significant effect on growth and survival, and the random effect of provenance has a significant effect on growth. Standard deviations, pseudo-r-squared values, and variance components reveal that the effect of plantation on the response to climatic distance was large in all models, indicating that management of site conditions could be used to potentially ameliorate the negative effects of climate change on growth and survival of these species. Finally, models suggest that assisted migration may not be necessary to maintain survival under climate change.