Aspen Bibliography

Acclimation in Plant Growth and Its Determinants to Elevated Carbon Dioxide and Temperature: Interspecific Variation Among Five Boreal Tree Species (Populus Tremuloides, Betula Papyrifera, Larix Laricina, Pinus Banksiana, Picea Mariana)

Document Type

Thesis/Dissertation

Source

University of Minnesota, Ph.D.

Journal/Book Title/Conference

DAI

Volume

58

Issue

7B

Publication Date

1997

Abstract

To test hypotheses concerning interspecific variation in response of trees to rising atmospheric concentrations of CO$\sb2$ and temperature, we compared growth and CO$\sb2$ exchange traits of five tree species of the North American boreal forest. Populus tremuloides, Betula papyrifera, Larix laricina, Pinus banksiana and Picea mariana were grown from seed in controlled environments under current ambient and elevated concentrations of CO$\sb2$ (370 and 580 $\mu$mol mol$\sp-1)$ combined with five temperature treatments from 18/12 to 30/24$\sp\circ$C.

Growth increases under CO$\sb2$ enrichment were minimal at the lowest temperature and maximum among the intermediate temperatures, corresponding with species differences in optimal growth temperatures. CO$\sb2$ enrichment stimulated growth through increases in whole-plant net assimilation rate of 22 percent, despite an 11 percent reduction in leaf area ratio under high CO$\sb2$. Reduced leaf area ratio under CO$\sb2$ enrichment resulted from a 10 percent decline in specific leaf area, whereas proportional allocation of dry mass to leaves did not vary between CO$\sb2$ treatments. Initially, proportional increases in dry mass under elevated CO$\sb2$ were greater for faster-growing broadleaved species than slower-growing conifers. However, growth increases under CO$\sb2$ enrichment eroded through time among broadleaved species. Species differences in ontogenetic drift in relative growth rate and leaf area ratio influenced the time course of growth differences under CO$\sb2$ enrichment.

Growth increases under elevated CO$\sb2$ resulted from increased net CO$\sb2$ uptake. Among species, rates of photosynthesis increased between 8 to 36 percent under CO$\sb2$ enrichment. Paralleling growth responses, proportional enhancements in net photosynthesis under elevated CO$\sb2$ were greater for the slower-growing conifers than faster-growing broadleaved species, reflecting varying degrees of acclimation to growth CO$\sb2$ concentration.

Rates of plant dark respiration were not affected by CO$\sb2$ concentration. Among species, respiration was positively correlated with relative growth rate. Maintenance respiration increased at higher growth temperatures. Growth respiration was not altered by temperature or CO$\sb2$. Respiration acclimated to thermal environment, owing to down-regulation at higher temperatures. Acclimation was associated with declines in foliar nitrogen concentration at higher growth temperatures. Interspecific variation in growth traits and acclimation of respiration to thermal environment are critical determinants of plant response to global change.

Comments

This is a thesis written in partial fulfillment of the requirements for the degree of Doctor of Philosophy

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