Keynote Presentations from the AVEC International Summer School, Peyresq, 14-27 September 2003

Speaker: Christian Körner
ch.koerner<at>unibas.ch
Botanisches Institut der Universität Basel, Schönbeinstrasse 6, CH-4056 Basel, Switzerland

Title of the talk: CO₂-increase and biodiversity - a vulnerability problem (pdf: 200KB)

Summary of the talk by a student: Students´ summary (pdf)

Abstract

CO₂-increase and biodiversity - a vulnerability problem

When elevated atmospheric CO₂ is mentioned, most people primarily think of global warming and the greenhouse effect. Not so plant biologists. For them, first of all, CO₂ is the prime 'food' of plants, the concentration of which has gone up by 30 % during the life span of a trees. What ever the indirect effects of CO₂-enrichment of the atmosphere to the climate system might be, we deal with a fundamental dietary change of the biosphere. CO₂-enrichment research has in large been focussing on the question of whether plants grow more in a CO₂-rich atmosphere. In the meanwhile it became clear that this question (and its answers) loses significance, unless two key issues are accounted for: (1) The nutritional status of a plant, which pre-defines its growth response to CO₂ - a challenge for experimentalists and modellers using such data for 'real world' scenarios, and (2) that species differ in their response. It is obvious that when species in a community will not show identical responses, there will be a change in community composition, sooner or later. Since plant nutrition and CO₂-enrichment alone as well as their interaction exert biodiversity responses, atmospheric CO₂ enrichment with and without N-deposition are key biodiversity issues. Since ecosystem functioning depends on the presence and abundance of certain species, biodiversity changes can change ecosystem vulnerability to certain environmental impacts. There is another aspect often overlooked when CO₂ comes into play: CO₂ enrichment commonly reduces stomatal opening and thus, plant water consumption. The emerging soil moisture effects can and do translate into biodiversity changes as well. Mesic species take an advantage over drought resistant species, an obvious vulnerability issue. Finally, there is evidence that exposure of plants to elevated CO₂ makes them slightly more vulnerable by freezing temperatures. I will underpin these insights with examples for a temperate calcareous grassland and for temperate and humid tropical forests.

Recommended background literature on this presentation:

• Granados J, Körner C (2002) In deep shade, elevated CO2 increases the vigor of tropical climbing plants. Glob Change Biol 8:1109-1117. doi:10.1046/j.1365-2486.2002.00533.x


• Körner C (2000) Biosphere responses to CO₂ enrichment. Ecol Appl 10:1590-1619.


• Körner C (2002) Grassland in a CO₂-enriched world. In: Durand J-L, Emile J-C, Huyghe C, Lemaire G (eds) Multi-function grasslands. Quality forages, animal products and landscapes. Imprimerie P. Oudin, Poitiers, p. 611-624.


• Körner C (2003) Ecological impacts of atmospheric CO2 enrichment on terrestrial ecosystems. Phil Trans R Soc Lond A 361: 2023-2041. doi:10.1098/rsta.2003.1241


• Körner C (2003) Carbon limitation in trees. J Ecol 91:4-17. doi:10.1046/j.1365-2745.2003.00742.x


• Obrist D, Arnone III JA, Körner C (2001) In situ effects of elevated atmospheric CO₂ on leaf freezing resistance and carbohydrates in a native temperate grassland. Ann Bot 87:839-844.

AVEC is a EU FP5 Concerted Action No. EVK2-2001-00074

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