CLIMATIC EFFECTS ON THE DELTA-O-18 AND DELTA-C-13 OF CELLULOSE IN THEDESERT TREE TAMARIX JORDANIS

The C-13/C-12 and O-18/O-16 ratios of stem cellulose of Tamarix jordan is (a tree common in wadis of arid regions) increased with decreasing relative humidity (RH) in individual trees growing along a climatic gr adient in Israel. The response to RH observed in the delta(18)O of the wood cellulose was strongly similar to that observed in leaf water ov er a diurnal cycle. Most of the data for delta(13)C and all of the dat a for delta(18)O could be fitted to two independent linear equations t hat, combined, allowed the reconstruction of RH and the delta(18)O of source water from the isotopic composition of ancient T. jordanis wood previously reported from the ancient fortress of Masada. Since the Ro man period, RH at Masada decreased by about 17%, while the delta(18)O value of local groundwater remained similar to present-day values, sug gesting that changing atmospheric circulation has played a role in cli mate change in the Middle East over the past two millennia.