Leaf and ecosystem response to soil water availability in mountain grasslands.
Climate change is expected to affect the Alps by increasing the frequency and intensity of summer drought events with negative impacts on ecosystem water resources. The response of CO2and H2O exchange of a mountain grassland to natural fluctuations of soil water content was evaluated during 2001-2009. In addition, the physiological performance of individual mountain forb and graminoid plant species under progressive soil water shortage was explored in a laboratory drought experiment. During the 9-year study period the natural occurrence of moderately to extremely dry periods did not lead to substantial reductions in net ecosystem CO2exchange and evapotranspiration. Laboratory drought experiments confirmed that all the surveyed grassland plant species were insensitive to progressive soil drying until very low soil water contents (<0.01 m3m-3) were reached after several days of drought. In field conditions, such a low threshold was never reached. Re-watering after a short-term drought event (5±1 days) resulted in a fast and complete recovery of the leaf CO2and H2O gas exchange of the investigated plant species. We conclude that the present-day frequency and intensity of dry periods does not substantially affect the functioning of the investigated grassland ecosystem. During dry periods the observed "water spending" strategy employed by the investigated mountain grassland species is expected to provide a cooling feedback on climate warming, but may have negative consequences for down-stream water users.
Ionicon Analytik GmbH, Eduard-Bodem-Gasse 3, 6020 Innsbruck, AUSTRIA.
Federico
F
Brilli
Institute of Ecology, University of Innsbruck, Sternwartestr. 15, 6020 Innsbruck, AUSTRIA.
Lukas
L
Hörtnagl
Institute of Ecology, University of Innsbruck, Sternwartestr. 15, 6020 Innsbruck, AUSTRIA.
Albin
A
Hammerle
Institute of Ecology, University of Innsbruck, Sternwartestr. 15, 6020 Innsbruck, AUSTRIA.
Alois
A
Haslwanter
Institute of Ion Physics and Applied Physics, University of Innsbruck, Technikerstr. 25, 6020 Innsbruck, AUSTRIA.
Armin
A
Hansel
National Research Council, Institute for the Protection of Plants, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze, ITALY.
Francesco
F
Loreto
Institute of Ecology, University of Innsbruck, Sternwartestr. 15, 6020 Innsbruck, AUSTRIA.
Georg
G
Wohlfahrt
climate change; drought; evapotranspiration; montane ecosystem; photosynthesis