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Title:
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The combined effects of a long-term experimental drought and an extreme drought on the use of plant-water sources in a Mediterranean forest
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Author:
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Barbeta, Adrià; Mejía Chang, Monica; Ogaya Inurrigarro, Romà; Voltas Velasco, Jordi; Dawson, Todd E.; Peñuelas, Josep
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Notes:
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Vegetation in water-limited ecosystems relies strongly on access to deep water reserves to withstand dry periods. Most of these ecosystems have shallow soils over deep groundwater reserves. Understanding the functioning and functional plasticity of species-specific root systems and the patterns of or differences in the use of water sources under more frequent or intense droughts is therefore necessary to properly predict the responses of seasonally dry ecosystems to future climate. We used stable isotopes to investigate the seasonal patterns of water uptake by a sclerophyll forest on sloped terrain with shallow soils. We assessed the effect of a long-term experimental drought (12 years) and the added impact of an extreme natural drought that produced widespread tree mortality and crown defoliation. The dominant species, Quercus ilex, Arbutus unedo and Phillyrea latifolia, all have dimorphic root systems enabling them to access different water sources in space and time. The plants extracted water mainly from the soil in the cold and wet seasons but increased their use of groundwater during the summer drought. Interestingly, the plants subjected to the long-term experimental drought shifted water uptake toward deeper (10-35 cm) soil layers during the wet season and reduced groundwater uptake in summer, indicating plasticity in the functional distribution of fine roots that dampened the effect of our experimental drought over the long term. An extreme drought in 2011, however, further reduced the contribution of deep soil layers and groundwater to transpiration, which resulted in greater crown defoliation in the drought-affected plants. The present study suggests that extreme droughts aggravate moderate but persistent drier conditions (simulated by our manipulation) and may lead to the depletion of water from groundwater reservoirs and weathered bedrock, threatening the preservation of these Mediterranean ecosystems in their current structures and compositions.
This research was supported by the Spanish Government projects CGL2010-17172 and 609 Consolider Ingenio Montes (CSD2008-00040), by the Catalan Government project SGR 610 2009-458 and the European Research Council Synergy grant ERC-2013-SyG-610028 611 IMBALANCE-P. A.B. acknowledges an FPI predoctoral fellowship from the Spanish 612 Ministry of Economy and Competitiveness that supported his visit to UC Berkeley. |
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Subject(s):
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-Holm oak
-Experimental drought
-Stable isotopes
-Water uptake |
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Rights:
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(c) Wiley, 2015
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Document type:
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article
acceptedVersion |
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Published by:
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Wiley
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Share:
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