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CR 41:221-232 (2010)  -  DOI:

Transient responses to increasing CO2 and climate change in an unfertilized grass–clover sward

Patrick Lazzarotto1, Pierluigi Calanca1,*, Mikhail Semenov2, Jürg Fuhrer1

1Agroscope Reckenholz-Tänikon Research Station ART, Air Pollution/Climate Group, Reckenholzstrasse 191, 8046 Zurich, Switzerland
2Centre for Mathematical and Computational Biology, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
*Corresponding author. Email:

ABSTRACT: Mechanisms controlling transient responses to elevated CO2 concentration and climate change in an unfertilized grassland on the Swiss Plateau were examined in light of simulations with PROGRASS, a process-based model of grass–clover interactions. Daily weather for a series of transient climate scenarios spanning the 21st century were developed for the study site with the help of the LARS-WG weather generator. Changes in the length of dry and wet spells, temperature, precipitation and solar radiation defining the scenarios were obtained from regional climate simulations carried out in the framework of the PRUDENCE project. Compared to 1961–1990, the latter indicated that for 2071–2100 there would be a noticeable increase in temperature (roughly 3°C in winter and 5°C in summer), a significant drop in summer precipitation (of the order of –30%) and a nearly 2-fold increase in the length of dry spells. Assuming that clover is less drought-tolerant than grass, we examined whether clover abundance would decrease as a consequence of increasing heat and water stress, or be promoted on account of CO2 stimulation. Results indicated that: (1) at our site, climate change alone did not curtail biological N2 fixation to the point as to alter the composition of the sward but nevertheless entailed a decrease in grassland productivity; (2) increasing CO2 clearly promoted clover growth (via feedbacks on nitrogen acquisition) and grassland productivity; and (3) even with CO2 stimulation, the additional N input from symbiotic N2 fixation was not sufficient to substantially improve the mineral N status of the system and promote grass competitiveness.

KEY WORDS: Climate change  · Elevated CO2 · Grassland productivity · Biological N2 fixation · Grass–clover interactions · Transient responses

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Cite this article as: Lazzarotto P, Calanca P, Semenov M, Fuhrer J (2010) Transient responses to increasing CO2 and climate change in an unfertilized grass–clover sward. Clim Res 41:221-232.

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