Interactive effects of elevated CO2, warming, and drought on photosynthesis of Deschampsia flexuosa in a temperate heath ecosystem

Abstract

Global change factors affect plant carbon uptake in concert. In order to investigate the response directions and potential interactive effects, and to understand the underlying mechanisms, multifactor experiments are needed. The focus of this study was on the photosynthetic response to elevated CO2 [CO2; free air CO2 enrichment (FACE)], drought (D; water-excluding curtains), and night-time warming (T; infrared-reflective curtains) in a temperate heath. A/Ci curves were measured, allowing analysis of light-saturated net photosynthesis (Pn), light- and CO2-saturated net photosynthesis (Pmax), stomatal conductance (gs), the maximal rate of Rubisco carboxylation (Vcmax), and the maximal rate of ribulose bisphosphate (RuBP) regeneration (Jmax) along with leaf δ13C, and carbon and nitrogen concentration on a monthly basis in the grass Deschampsia flexuosa. Seasonal drought reduced Pn via gs, but severe (experimental) drought decreased Pn via a reduction in photosynthetic capacity (Pmax, Jmax, and Vcmax). The effects were completely reversed by rewetting and stimulated Pn via photosynthetic capacity stimulation. Warming increased early and late season Pn via higher Pmax and Jmax. Elevated CO2 did not decrease gs, but stimulated Pn via increased Ci. The T×CO2 synergistically increased plant carbon uptake via photosynthetic capacity up-regulation in early season and by better access to water after rewetting. The effects of the combination of drought and elevated CO2 depended on soil water availability, with additive effects when the soil water content was low and D×CO2 synergistic stimulation of Pn after rewetting. The photosynthetic responses appeared to be highly influenced by growth pattern. The grass has opportunistic water consumption, and a biphasic growth pattern allowing for leaf dieback at low soil water availability followed by rapid re-growth of active leaves when rewetted and possibly a large resource allocation capability mediated by the rhizome. This growth characteristic allowed for the photosynthetic capacity up-regulations that mediated the T×CO2 and D×CO2 synergistic effects on photosynthesis. These are clearly advantageous characteristics when exposed to climate changes. In conclusion, after 1 year of experimentation, the limitations by low soil water availability and stimulation in early and late season by warming clearly structure and interact with the photosynthetic response to elevated CO2 in this grassland species.

Atmospheric CO2 Alters Resistance of Arabidopsis to Pseudomonas syringae by Affecting Abscisic Acid Accumulation and Stomatal Responsiveness to Coronatine

“…Also the dry weight of the rosettes was significantly lower in the low CO 2 condition ( Figure 1B ). In contrast, there were no effects on rosette growth under high CO 2 conditions, which was rather unexpected since most previous studies have reported an increase in biomass (Bowes, 1991; Leakey et al, 2009). However, our experimental conditions may not have been optimal for stimulated growth by elevated CO 2 (Temme et al, 2015) and moreover, the Col-0 accession that we used may respond differently to high CO 2 than other plant species (Li et al, 2006; Leakey et al, 2009; Temme et al, 2015).…”

Root growth and N dynamics in response to multi-year experimental warming, summer drought and elevated CO2 in a mixed heathland-grass ecosystem

“…In the CLIMAITE experiment, Albert et al (2011aAlbert et al ( , 2011b found increased net photosynthesis and increased leaf C : N ratios in response to elevated CO 2. This is comparable to our higher root C : N ratio, which supports our hypothesis of the improved carbon status of the plant and a higher C allocation to roots grown under elevated CO 2 .…”

“…We hypothesised that root growth would be stimulated in response to elevated CO 2 due to increased C uptake (Albert et al 2011a;Albert et al 2011b), and that therefore there would be greater C allocation to the roots. Drought was expected to slow down root growth, whereas the temperature treatment was expected to increase root growth, depending on soil moisture content.…”

Positive effects of night warming on physiology of coniferous trees in late growing season: Leaf and root

“…Previous studies about the effect of experimental warming on tree species have focused primarily on net mineralization, net nitrification and denitrification rates, ectomycorrhizal colonization and root exudation in early growing season, peak of growing season and non-growing season (Zhao and Liu, 2009;Yin et al, 2012Yin et al, , 2013Yin et al, , 2014. Global warming affects plant growth through direct effects on photosynthesis and respiration (Albert et al, 2011) and indirect effects on soil nitrogen availability (Sardans et al, 2008) and soil moisture (Holsten et al, 2009). Previous study reported that an increase in autumn temperature did not increase the photosynthetic rate but affects the consumption of excess energy in seedlings of Jack pine (Busch et al, 2007).…”