Increased water-use efficiency translates into contrasting growth patterns of Scots pine and sessile oak at their southern distribution limits

In forests, the increase in atmospheric CO2 concentrations (Ca ) has been related to enhanced tree growth and intrinsic water-use efficiency (iWUE). However, in drought-prone areas such as the Mediterranean Basin, it is not yet clear to what extent this "fertilizing" effect may compensate for drought-induced growth reduction. We investigated tree growth and physiological responses at five Scots pine (Pinus sylvestris L.) and five sessile oak (Quercus petraea (Matt.) Liebl.) sites located at their southernmost distribution limits in Europe for the period 1960-2012 using annually resolved tree-ring width and δ13 C data to track ecophysiological processes. Results indicated that all 10 natural stands significantly increased their leaf intercellular CO2 concentration (Ci ), and consequently iWUE. Different trends in the theoretical gas-exchange scenarios as a response to increasing Ca were found: generally, Ci tended to increase proportionally to Ca , except for trees at the driest sites in which Ci remained constant. Ci from the oak sites displaying higher water availability tended to increase at a comparable rate to Ca . Multiple linear models fitted at site level to predict basal area increment (BAI) using iWUE and climatic variables better explained tree growth in pines (31.9%-71.4%) than in oak stands (15.8%-46.8%). iWUE was negatively linked to pine growth, whereas its effect on growth of oak differed across sites. Tree growth in the western and central oak stands was negatively related to iWUE, whereas BAI from the easternmost stand was positively associated with iWUE. Thus, some Q. petraea stands might have partially benefited from the "fertilizing" effect of rising Ca , whereas P. sylvestris stands due to their strict closure of stomata did not profit from increased iWUE and consequently showed in general growth reductions across sites. Additionally, the inter-annual variability of BAI and iWUE displayed a geographical polarity in the Mediterranean.

Bibliographic Details

Main Authors:	Martínez-Sancho, E., Dorado-Liñán, I., Gutiérrez Merino, E., Matiu, M., Helle, G., Heinrich, I., Menzel, A.
Format:	artículo biblioteca
Language:	English
Published:	Wiley 2018
Subjects:	Basal area increment, Carbon isotope discrimination, Mediterranean Basin, Pinus sylvestris, Quercus petraea, Tree rings,
Online Access:	http://hdl.handle.net/20.500.12792/650 http://hdl.handle.net/10261/290857
Tags:	Add Tag No Tags, Be the first to tag this record!