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 |
| |
Authors: | Maseyk Kadmiel Hemming Debbie Angert Alon Leavitt Steven W Yakir Dan |
| |
Institution: | (1) Department of Environmental Sciences and Energy Research, Weizmann Institute of Science, 76100 Rehovot, Israel;(2) Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ 85721, USA;(3) Present address: BIOEMCO (UMR 7618), Universit? Pierre et Marie Curie, 78850 Thiverval-Grignon, France;(4) Present address: Met Office Hadley Centre, Fitzroy Road, Exeter, UK;(5) Present address: Institute of Earth Sciences, Hebrew University, Jerusalem, Israel; |
| |
Abstract: | 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 CO2 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. |
| |
Keywords: | |
本文献已被 PubMed SpringerLink 等数据库收录! |
|