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Effects of elevated CO 2 on leaf gas exchange in beech and oak at two levels of nutrient supply: consequences for sensitivity to drought in beech
Author(s) -
HEATH J.,
KERSTIENS G.
Publication year - 1997
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.1997.d01-13.x
Subject(s) - beech , fagus sylvatica , quercus robur , nutrient , photosynthesis , stomatal conductance , fagaceae , growing season , population , botany , agronomy , horticulture , chemistry , biology , ecology , demography , sociology
Beech ( Fagus sylvatica L.) and pedunculate oak ( Quercus robur L.) were grown from seed for two whole seasons at two CO 2 concentrations (ambient and ambient + 250 μmol mol −1 ) with two levels of soil nutrient supply. Measurements of net leaf photosynthetic rate ( A ) and stomatal conductance ( g s ) of well‐watered plants were taken over both seasons; a drought treatment was applied in the middle of the second growing season to a separate sample of beech drawn from the same population. The net leaf photosynthetic rate of well‐watered plants was stimulated in elevated CO 2 by an average of 75% in beech and 33% in oak; the effect continued through both growing seasons at both nutrient levels. There were no interactive effects of CO 2 concentration and nutrient level on A or g s in beech or oak. Stomatal conductance was reduced in elevated CO 2 by an average of 34% in oak, but in beech there were no significant reductions in g s except under cloudy conditions (–22% in elevated CO 2 ). During drought, there was no effect of CO 2 concentration on g s in beech grown with high nutrients, but for beech grown with low nutrients, g s was significantly higher in elevated CO 2 , causing more rapid soil drying. With high nutrient supply, soil drying was more rapid at elevated CO 2 due to increased leaf area. It appears that beech may substantially increase whole‐plant water consumption in elevated CO 2 , especially under conditions of high temperature and irradiance when damage due to high evaporative demand is most likely to occur, thereby putting itself at risk during periods of drought.