EFFECTS OF ELEVATED ATMOSPHERIC CO2 ON MATURE PLANT RESPONSES IN A NATIVE AUSTRALIAN EUCALYPTUS FOREST (EUCFACE)

Carey, Kayla AH

Undergraduate Honors Thesis

EFFECTS OF ELEVATED ATMOSPHERIC CO2 ON MATURE PLANT RESPONSES IN A NATIVE AUSTRALIAN EUCALYPTUS FOREST (EUCFACE) Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/undergraduate_honors_theses/s1784m27h

Abstract

Rising atmospheric carbon dioxide (CO₂) concentrations are associated with rising global temperatures; these changes alter ecological communities in ways that vary among plant species and environmental conditions. Research on the response of various plant species to elevated CO₂ concentration is needed to predict future implications of climate change on ecosystems. Free-Air-CO₂ Enrichment (FACE) experiments examine the effects of elevated atmospheric CO₂ levels on terrestrial ecosystems by manipulating atmospheric CO₂ concentration of native vegetation.

The present study was the first ever FACE experiment in a mature Australian Eucalyptus woodland and simulated an ecosystem exposed to CO₂ levels of 550 parts per million (ppm), which is the projected global atmospheric CO₂ concentration for 2050. Control plots were exposed to un-manipulated atmospheric CO₂ levels of approximately 400 ppm. The influence of elevated atmospheric CO₂ on the ecosystem was assessed by analyzing photosynthesis rates, radial tree growth (trunk circumference and calculated stem-basal area growth), and photosynthetic water-use efficiency (the ratio of photosynthetic CO₂ uptake to transpirational water loss). This approach led to three major findings: elevated CO₂ (1) caused photosynthesis to be modestly (2.7%), albeit significantly, higher, (2) did not have an effect on radial tree growth, and (3) was associated with a significantly lower stomatal conductance and greater photosynthetic water-use efficiency. The results of this study are discussed in the context of plant-species-specific differences in the response to elevated CO₂ and elevated temperatures at the ecosystem level.

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