Citation
Calvete Sogo, Hector and Elvira, S. and Sanz, Javier and González-Fernández, I. and García Gómez, Hector and Sánchez Martín, Laura and Alonso, R. and Bermejo, V.
(2014).
Current ozone levels threaten gross primary production and yield of Mediterranean annual pastures and nitrogen modulates the response.
"Atmospheric Environment", v. 95
;
pp. 197-206.
ISSN 1352-2310.
https://doi.org/10.1016/j.atmosenv.2014.05.073.
Abstract
Pastures are among the most important ecosystems in Europe considering their biodiversity and dis-
tribution area. However, their response to increasing tropospheric ozone (O
3
) and nitrogen (N) deposi-
tion, two of the main drivers of global change, is still uncertain. A new Open-Top Chamber (OTC)
experiment was performed in central Spain, aiming to study annual pasture response to O
3
and N in close
to natural growing conditions. A mixture of six species of three representative families was sowed in the
fi
eld. Plants were exposed for 40 days to four O
3
treatments:
fi
ltered air, non-
fi
ltered air (NFA) repro-
ducing ambient levels and NFA supplemented with 20 and 40 nl l
�
1
O
3
. Three N treatments were
considered to reach the N integrated doses of
“
background
”
,
þ
20 or
þ
40 kg N ha
�
1
. Ozone signi
fi
cantly
reduced green and total aboveground biomass (maximum reduction 25%) and increased the senescent
biomass (maximum increase 40%). Accordingly, O
3
decreased community Gross Primary Production due
to both a global reduction of ecosystem CO
2
exchange and an increase of ecosystem respiration. Nitrogen
could partially counterbalance O
3
effects on aboveground biomass when the levels of O
3
were moderate,
but at the same time O
3
exposure reduced the fertilization effect of higher N availability. Therefore, O
3
must be considered as a stress factor for annual pastures in the Mediterranean areas.