Environmental and stomatal control of photosynthetic enhancement in the canopy of a sweetgum (Liquidambar styraciflua L.) plantation during 3 years of CO₂ enrichment

Abstract

Light-saturated photosynthetic and stomatal responses to elevated CO 2 were measured in upper and mid-canopy foliage of a sweetgum ( Liquidambar styraciflua L) plantation exposed to free-air CO 2 enrichment (FACE) for 3 years, to characterize environmental interactions with the sustained CO 2 effects in an intact deciduous forest stand. Responses were evaluated in relation to one another, and to seasonal patterns and natural environmental stresses, including high temperatures, vapour pressure deficits ( VPD ), and drought. Photosynthetic CO 2 assimilation ( A ) averaged 46% higher in the +200 µ µ µ µ mol mol − 1 ), but relative effects, as the ratio of elevated to ambient rates, varied greatly under those conditions. Both stomatal and non-stomatal limitations of A were involved during late season droughts. Leaf temperature had a limited influence on A and g s , and there was no detectable relationship between prevailing temperature and CO 2 effects on A or g s . The responsiveness of A and g s to elevated CO 2 , both absolute and relative, was maintained through time and within the canopy of this forest stand, subject to seasonal constraints and variability associated with limiting air and soil moisture.

Predicting the future of forests in the Mediterranean under climate change, with niche- and process-based models: CO2 matters!

“…It also improves nitrogen-use efficiency at both the leaf and canopy scale, while stimulating dark respiration via a transcriptional reprogramming of metabolism (Leakey et al, 2009). Experimental results indicate that plants are able to increase their water-use efficiency (WUE) as CO 2 levels rise (e.g., Picon et al, 1996;Morison, 1998), as has been corroborated under field conditions (Peñ uelas & Azcó n-Bieto, 1992;Ehrlinger & Cerling, 1995;Duquesnay et al, 1998;Gunderson et al, 2002;Ainsworth & Rogers, 2007). Studies have also identified interspecies variability in responses to increasing atmospheric CO 2 concentrations (e.g., Francey & Farquhar, 1982), and, importantly, have highlighted the possibility of species-specific response saturation rates (Waterhouse et al, 2004;Betson et al, 2007).…”

Global effects of doubled atmospheric CO2 content on evapotranspiration, soil moisture and runoff under potential natural vegetation

“…In other words, the water use efficiency of plants is increased at high [CO 2 ]. Reductions in stomatal conductance induced by this physiological CO 2 effect are typically in the order of 10-40% (Morison, 1985;Field et al, 1995;Drake & Gonzàles-Meler, 1997;Medlyn et al, 2001;Gunderson et al, 2002).…”

Respostas fotossintéticas e de crescimento da espécie amazônica Senna reticulata sob elevada concentração de CO2

“…Resultados semelhantes foram encontrados para Liquidambar styraciflua cultivadas em FACE sob elevado CO 2 , onde a redução na condutância é menor em relação ao tratamento ambiente (Gunderson et al, 2002;Wullschleger et al, 2002;Herrick et al, 2004). Em experimentos com plantas cultivadas sob elevado CO 2 , em períodos de seca, foi observado que a resposta ao CO 2 é maior devido à baixa condutância das plantas desse tratamento (Gunderson et al, 2002;Leakey et al, 2004Leakey et al, , 2006.…”