Influence of species interactions on transpiration of Mediterranean tree species during a summer drought
Recent research has shown that interactions between species with different functional traits can promote forest ecosystem processes. In the context of climate change, understanding whether species interactions in mixed-species ecosystems can improve the adaptation of these ecosystems to extreme climatic events is crucial to developing new management strategies. In this study, we investigated the impact of species interactions on the sap flux density of three Mediterranean tree species (Quercus faginea, Pinus nigra and Pinus sylvestris) during a summer drought. Measurements of foliar carbon isotopic composition (δ 13C) were also conducted on the same trees. The decline in transpiration during drought was the greatest for P. sylvestris and the least pronounced for Q. faginea. For P. nigra and Q. faginea, the decrease in transpiration as the drought progressed was lower when these species where interacting with another tree species, particularly with P. sylvestris. In contrast, the decrease for P. sylvestris was higher when this species was interacting with another species. Differing drought effects were consistent with the δ 13C values. We showed that the identity of the species present in the direct neighbourhood of a given tree can differentially influence water availability and water-use of these three co-existing Mediterranean tree species during a summer drought. Our findings suggest that species interactions play an important role in modulating the response of tree species to drought. Favouring tree species diversity in this region does not seem to be systematically beneficial in terms of soil water availability and water-use for all the interacting species.
KeywordsComplementarity Competition Facilitation Species interaction Drought Transpiration δ13C
We thank Miguel Fernández and David L. Quiroga for their technical assistance. We thank the technical Isotope Platform of INRA Nancy for the carbon isotope analyses. A.F. was supported by JAE-PREDOC from CSIC and co-funded by the European Union (Fondo Social Europeo). This work was conducted in the framework of the ARBRE Laboratory of Excellence project (ANR-12-LABXARBRE-01) supported by the French National Research Agency. The research leading to these results was conducted within the FunDiv EUROPE project and has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under Grant agreement No 265171.
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