Adattamenti all’aridità e risposte ai cambiamenti climatici in tre specie arbustive di gariga
Author(s)
Liberati, Dario
Date Issued
April 13, 2012
Type
Doctoral Thesis
Abstract
In order to investigate how the forecast temperature increase and rainfall reduction could affect Mediterranean shrubland ecosystems, the adaptions of Cistus monspeliensis L. (Cistaceae), Dorycnium pentaphyllum Scop. (Fabaceae) and Helichrysum italicum subsp. microphyllum (Willd.) (Asteraceae), to the actual Mediterranean climate, as well as their responses to manipulation of minimum temperature (+0.9 °C) and rainfall (- 20 %), were studied from 2009 to 2011 in a garrigue ecosystem, located in the NW of Sardinia . Gas exchange at leaf level and pre-dawn leaf water potential were monitored in the three species. In addition, photosynthetic capacity, maximum quantum yield of PSII, carbon and nitrogen leaf content and morphology at leaf and shoot level were also recorded in C. mospeliensis. The comparison among species, based on photosynthesis and water potential, identified H. italicum (shallow rooted species) as the most sensitive species to the natural and simulated drought, because of the strong reduction of gas exchange rates during drought and the slow recovery in Autumn, and D. pentaphyllum (deep rooted species) as the most resistant one, whit the littlest reduction of photosynthesis rates in summer.
As H. italicum, C. monspeliensis (shallow rooted species) showed a strong reduction of CO2 assimilation rates during drought, mainly explained by stomatal limitations and LMA increase, but also a quick recovery in Autumn, connected to the lamina expansion in the high LMA summer leaves. In this species the drought treatment induced photosynthesis acclimation to water stress and a delayed Autumn recovery, while warming treatment an increase of the photosynthetic capacity, leaf nitrogen content and shoot and leaf size, maybe connected to an enhancement of soil nitrogen mineralization rates.
Additional information
Dottorato di ricerca in Ecologia forestale
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