Increase in water-use efficiency and underlying processes in pine forests across a precipitation gradient in the dry Mediterranean region over the past 30 years

Kadmiel Maseyk, Debbie Hemming, Alon Angert, Steven Leavitt, Dan Yakir

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64 Scopus citations


Motivated by persistent predictions of warming and drying in the entire Mediterranean and other regions, we have examined the interactions of intrinsic water-use efficiency (W i) with environmental conditions in Pinus halepensis. We used 30-year (1974-2003) tree-ring records of basal area increment (BAI) and cellulose 13C and 18O composition, complemented by short-term physiological measurements, from three sites across a precipitation (P) gradient (280-700 mm) in Israel. The results show a clear trend of increasing W i in both the earlywood (EW) and latewood (LW) that varied in magnitude depending on site and season, with the increase ranging from ca. 5 to 20% over the study period. These W i trends were better correlated with the increase in atmospheric CO 2 concentration, C a, than with the local increase in temperature (~0.04°C year -1), whereas age, height and density variations had minor effects on the long-term isotope record. There were no trends in P over time, but W i from EW and BAI were dependent on the interannual variations in P. From reconstructed C i values, we demonstrate that contrasting gas-exchange responses at opposing ends of the hydrologic gradient underlie the variation in W i sensitivity to C a between sites and seasons. Under the mild water limitations typical of the main seasonal growth period, regulation was directed at increasing C i/C a towards a homeostatic set-point observed at the most mesic site, with a decrease in the W i response to C i with increasing aridity. With more extreme drought stress, as seen in the late season at the drier sites, the response was W i driven, and there was an increase in the W i sensitivity to C a with aridity and a decreasing sensitivity of C i to C a. The apparent C a-driven increases in W i can help to identify the adjustments to drying conditions that forest ecosystems can make in the face of predicted atmospheric change.

Original languageEnglish (US)
Pages (from-to)573-585
Number of pages13
Issue number2
Publication statusPublished - Oct 2011



  • Aleppo pine
  • CO fertilization
  • Dryland productivity
  • Isotope dendrology
  • Stomatal conductance

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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