Stock, William D.;
Ludwig, Fulco;
Morrow, Carl;
Midgley, Guy F.;
Wand, Stephanie J. E.;
Allsopp, Nicky;
Bell, Tina L.
Long-Term Effects of Elevated Atmospheric CO₂ on Species Composition and Productivity of a Southern African C₄ Dominated Grassland in the Vicinity of a CO₂ Exhalation
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Media type:
E-Article
Title:
Long-Term Effects of Elevated Atmospheric CO₂ on Species Composition and Productivity of a Southern African C₄ Dominated Grassland in the Vicinity of a CO₂ Exhalation
Contributor:
Stock, William D.;
Ludwig, Fulco;
Morrow, Carl;
Midgley, Guy F.;
Wand, Stephanie J. E.;
Allsopp, Nicky;
Bell, Tina L.
imprint:
Springer, 2005
Published in:Plant Ecology
Language:
English
ISSN:
1385-0237;
1573-5052
Origination:
Footnote:
Description:
<p> We describe the long-term effects of a CO₂ exhalation, created more than 70 years ago, on a natural C₄ dominated sub-tropical grassland in terms of ecosystem structure and functioning. We tested whether long-term CO₂ enrichment changes the competitive balance between plants with C₃ and C₄ photosynthetic pathways and how CO₂ enrichment has affected species composition, plant growth responses, leaf properties and soil nutrient, carbon and water dynamics. Long-term effects of elevated CO₂ on plant community composition and system processes in this sub-tropical grassland indicate very subtle changes in ecosystem functioning and no changes in species composition and dominance which could be ascribed to elevated CO₂ alone. Species compositional data and soil δ¹³C isotopic evidence suggest no detectable effect of CO₂ enrichment on C₃:C₄ plant mixtures and individual species dominance. Contrary to many general predictions C₃ grasses did not become more abundant and C₃ shrubs and trees did not invade the site. No season length stimulation of plant growth was found even after 5 years of exposure to CO₂ concentrations averaging 610 μmol mol⁻¹. Leaf properties such as total N decreased in the C₃ but not C₄ grass under elevated CO₂ while total non-structural carbohydrate accumulation was not affected. Elevated CO₂ possibly lead to increased end-of-season soil water contents and this result agrees with earlier studies despite the topographic water gradient being a confounding problem at our research site. Long-term CO₂ enrichment also had little effect on soil carbon storage with no detectable changes in soil organic matter found. There were indications that potential soil respiration and N mineralization rates could be higher in soils close to the CO₂ source. The conservative response of this grassland suggests that many of the reported effects of elevated CO₂ on similar ecosystems could be short duration experimental artefacts that disappear under long-term elevated CO₂ conditions. </p>