Masters Theses

Date of Award

5-2006

Degree Type

Thesis

Degree Name

Master of Science

Major

Forestry

Major Professor

Jennifer A. Franklin

Committee Members

Jake Weltzin, Dave Buckley

Abstract

Global air temperatures are predicted to rise 1° to 4.5°C by the year 2100 and perhaps greater at high latitudes. In order to correctly identify the effects of climate change on tree species, the present thesis is an assessment of the sensitivity, response and acclimation potential of southern Appalachian red spruce (Picea rubens Sarg.) to the impact of warming. This objective was approached through examinations of synthesis (instantaneous and short-term acclimation rates of photosynthesis and respiration) as well as investment (biomass accumulation and partitioning, growth rate, and carbohydrate allocation) of carbon assimilates.

Red spruce from two southern Appalachian provenances were germinated and grown in two separate growth chambers set at day/night temperatures of 19.9/12.9°C and 23.9/16.9°C (means of 17° and 21°C). At weeks 8, 12 and 16 after germination, concurrent analyses of carbon gas exchange and biomass accumulation were conducted. Seedlings grown at 21ºC had low photosynthetic rates at week 8, but fully acclimated by week 16 to rates equal to seedlings grown at 17ºC. Daytime dark respiration and Q10 values remained near equal throughout the study duration and showed minimal dependence on treatment temperature. Despite equivalent carbon assimilation, seedlings grown at the low temperature had significantly lower whole plant mass at every measurement date. Throughout the study duration, plants grown at 17ºC allocated more mass to roots, while seedlings in our elevated temperature partitioned more to foliage. Relative growth rate was 154% greater for plants grown at 21ºC than for plants at 17ºC. As supply of photosynthate surpassed growth demand for seedlings grown at low temperature conditions, these seedlings had higher concentrations of starch in both roots and shoots.

We conclude that carbon assimilation in southern Appalachian red spruce has the potential for physiological acclimation to temperature. As the cool adapted spruce seedlings performed better at 21ºC rather than at 17ºC, as displayed by increased growth rate and dry mass accumulation, we question the temperature limitations of the deciduous-boreal ecotone as it relates to this species. Interspecific variations to warmer temperatures leading to modifications in interspecific competition may be a greater determinate of a displacement of this ecotone.

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