Global Warming Can Negate the Expected CO2 Stimulation in Photosynthesis and Productivity for Soybean Grown in the Midwestern United States    

Abstract

Extensive evidence shows that increasing carbon dioxide concentration ([CO 2 ]) stimulates, and increasing temperature decreases, both net photosynthetic carbon assimilation (A) and biomass production for C 3 plants. However the [CO 2 ]-induced stimulation in A is projected to increase further with warmer temperature. While the influence of increasing temperature and [CO 2 ], independent of each other, on A and biomass production have been widely investigated, the interaction between these two major global changes has not been tested on field-grown crops. Here, the interactive effect of both elevated [CO 2 ] (approximately 585 mmol mol 21) and temperature (+3.5°C) on soybean (Glycine max) A, biomass, and yield were tested over two growing seasons in the Temperature by Free-Air CO 2 Enrichment experiment at the Soybean Free Air CO 2 Enrichment facility. Measurements of A, stomatal conductance, and intercellular [CO 2 ] were collected along with meteorological, water potential, and growth data. Elevated temperatures caused lower A, which was largely attributed to declines in stomatal conductance and intercellular [CO 2 ] and led in turn to lower yields. Increasing both [CO 2 ] and temperature stimulated A relative to elevated [CO 2 ] alone on only two sampling days during 2009 and on no days in 2011. In 2011, the warmer of the two years, there were no observed increases in yield in the elevated temperature plots regardless of whether [CO 2 ] was elevated. All treatments lowered the harvest index for soybean, although the effect of elevated [CO 2 ] in 2011 was not statistically significant. These results provide a better understanding of the physiological responses of soybean to future climate change conditions and suggest that the potential is limited for elevated [CO 2 ] to mitigate the influence of rising temperatures on photosynthesis, growth, and yields of C 3 crops.

Future threats to agricultural food production posed by environmental degradation, climate change, and animal and plant diseases – a risk analysis in three economic and climate settings

“…However, recent evidence suggests that elevated temperatures have a negative impact on the same physiological processes, and that the combined effect of both increased CO 2 and temperature may lead to decreased photosynthesis and biomass production (Ruiz-Vera et al 2013). In addition, heat stress during pollination will increase the vulnerability of several commodity crops (Sage and Kubien 2007;Semenov and Shewry 2011), especially in areas where crops are grown close to the critical temperature limit for photosynthesis (Ruiz-Vera et al 2013). In contrast, higher temperatures may prolong cultivation seasons and lead to higher yields in northern latitudes and colder areas (Eckersten et al 2011).…”

Modelling soybean yield responses to seeding date under projected climate change scenarios

“…It implies that the harvest index of soybean would decrease under future climate scenarios with increased temperature and CO 2 concentration. It has been reported that the harvest index of soybean decreases under doubling of the CO 2 concentration (Cure and Acock 1986), and with increased temperature through reductions of pod and seed numbers (Ruiz-Vera et al 2013;Tacarindua et al 2013). Ruiz-Vera et al (2013) concluded that under future climate conditions, the combined effects of elevated CO 2 concentration and higher temperature would likely reduce growth due to overriding environmental factors, but this conclusion was based on current crop cultivars.…”

“…It has been reported that the harvest index of soybean decreases under doubling of the CO 2 concentration (Cure and Acock 1986), and with increased temperature through reductions of pod and seed numbers (Ruiz-Vera et al 2013;Tacarindua et al 2013). Ruiz-Vera et al (2013) concluded that under future climate conditions, the combined effects of elevated CO 2 concentration and higher temperature would likely reduce growth due to overriding environmental factors, but this conclusion was based on current crop cultivars. From (Morrison et al 1999;Rowntree et al 2014), and breeding efforts to keep high harvest index will likely continue.…”

“…The harvest index of soybean has increased stably in the last century (Morrison et al 1999). It is reasonable to assume that breeding efforts may continue to improve or, at least maintain, the current harvest index levels by overcoming the potentially negative impacts of a future warmer climate (Cure and Acock 1986;Ruiz-Vera et al 2013;Tacarindua et al 2013). In scenario III, the seed yields were additionally modelled with the current harvest index levels that were simulated under the baseline climate conditions while all other conditions were kept the same as in scenario II.…”

Sezoninė C apykaita žolių ir kviečių agroekosistemose

“…Krituliai, nors ir negausūs, labai suaktyvina CO 2 emisijas iš dirvožemio (Lee et al, 2004;Yuste et al, 2003), o fotosintezės asimiliuotas CO 2 kiekis didėja priklausomai nuo šviesos intensyvumo iki šviesos įsotinimo tarpsnio. Fotosintezės asimiliuoto CO 2 kiekio intensyvumas priklauso ne tik nuo absorbuojamo anglies dioksido kiekio, bet ir nuo esamo drėgmės ir temperatūros, kuri tiesiogiai paveikia fermento aktyvumą (Ruiz-Vera et al, 2013). Tikslių anglies apykaitos duomenų intensyvios žemdirbystės pasėlių agroekosistemose nėra sukaupta, todėl sezoninis C apykaitos kitimo nustatymas būtų reikšmingas formuojant C balansą CO 2 emisijų mažinimo kryptimi bei prognozuojant jų pokyčius.…”