Temporal patterns of surface ozone levels in different habitats of the North Western Mediterranean basin

2004 ◽  
Vol 38 (7) ◽  
pp. 985-992 ◽  
Author(s):  
Àngela Ribas ◽  
Josep Peñuelas
1993 ◽  
Vol 20 (1) ◽  
pp. 117 ◽  
Author(s):  
JL Araus ◽  
R Buxo

Carbon isotope discrimination (Δ) was determined for kernels of six-row barley and durum wheat cultivated in the north-western Mediterranean basin during the last seven millennia. Samples from the Neolithic, Bronze, Iron and Middle Ages came from different archaeological sites in Catalonia. Samples for the period 1910-20 and 1990 were also analysed. There was a slight decrease (P=0.10, carbonisation-corrected values) in Δ from the Neolithic to the Iron Age period and a much steeper decrease from the Middle Ages to 1910-20 (P<0.01). Since water-use efficiency and isotope discrimination are negatively correlated, from the pattern of change in Δ it is suggested that there has been a progressive increase in the water-use efficiency (WUE) of these cereals. Since the Middle Ages this has coincided with increases in atmospheric CO2 concentration. Thus, for a given relative humidity and air temperature, the estimated WUE (measured as the ratio of CO2 assimilation to transpiration) from the Neolithic to the Middle Ages samples ranged between 65-70% of present time WUE values, whereas WUE for 1910-20 was about 86% of present values.


1995 ◽  
Vol 12 (6) ◽  
pp. 645-666 ◽  
Author(s):  
Alain Mauffret ◽  
Georges Pascal ◽  
Agnès Maillard ◽  
Christian Gorini

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