Interactive Effects of Warming and Elevated CO2 on a Tropical Forage Species

Paper Reviewed
Alzate-Marin, A.L., Rivas, P.M.S, Galaschi-Teixeira, J.S., Bonifácio-Anacleto, F., Silva, C.C., Schuster, I., Nazareno, A.G., Giuliatti, S., da Rocha Filho, L.C., Garófalo, C.A. and Martinez, C.A. 2021. Warming and elevated CO2 induces changes in the reproductive dynamics of a tropical plant species. Science of the Total Environment 768: 144899,

In a prior study (Habermann et al., 2019) it was found that moderate warming and elevated CO2 improved the growth and biomass production of Stylosanthes capitata under adequate soil nutrient and water availability conditions. In a follow up study, Alzate-Marin et al. (2021) investigated the effects of these same two abiotic factors on plant-pollinator interactions of this economically important tropical pasture and forage species.

The experiment was conducted under field conditions at the University of São Paulo Ribeirão Preto Campus (Ribeirão Preto, São Paulo State, Brazil). Two-month-old S. capitata plants were exposed to one of four treatment conditions, including control (ambient temperature and ambient CO2), elevated CO2 (EC, approximately 600 ppm), elevated temperature (ET, 2°C above ambient), or combined elevated CO2 and elevated temperature (ECO2 x ET). Elevated CO2 was applied using the Free-air CO2 Enrichment (FACE) design and elevated temperature was applied via infrared heaters. Plants remained under the various treatment conditions through the flowering period, during which time the authors collected data on the number of flowers produced, time of flower opening and closing, and floral visitors as related to plant reproduction.

Results of the study revealed that both warming and elevated CO2 had a positive effect on flower number, increasing the mean number per treatment by 39%, 62% and a whopping 137% in the ECO2, ET and ECO2 x ET treatments, respectively. Warming also advanced the time of flower opening and closing by approximately 1 hour, whereas elevated CO2 had no effect on this parameter. However, the total time of flower opening remained about the same among the four treatments at approximately 3 hours per day. And with respect to floral visitors, compared with control conditions this parameter was enhanced by 11%, 44% and 84% in the ECO2, ET and ECO2 x ET treatments, respectively.

Commenting on these several favorable findings, Alzate-Marin et al. say that “warming and elevated CO2 increased reproductive investment by boosting flower production.” And they add that “in terms of flower phenology, warming induced early flower opening [that] increased attractiveness for floral visitors and pollinators, which may be related to their preference for nectar that is warmer and with higher concentrations of sugar, which in turn may be linked to an increase in photosynthesis rate.” Consequently, the researchers conclude that “the effects of elevated CO2 and warming on plant-pollinator relationships for S. capitata suggest phenological adaptation by both the plant and its pollinators to future climate change scenarios.”

Figure 1. Average number of Stylosanthes capitata flowers per week in the control, elevated CO2 (ECO2), elevated temperature (ET) and combined elevated CO2 and elevated temperature (ECO2 x ET) treatments. Derived from data presented in Table 1 of Alzate-Marin et al. (2021).

Habermann, E., Oliveira, E.A.D., Contin, D.R., San Martin, J.A.B., Curtarelli, L., Gonzalez-Meler, M.A. and Martinez, C.A. 2019. Stomatal development and conductance of a tropical forage legume are regulated by elevated [CO2] under moderate warming. Frontiers of Plant Science 10: 1-17.

This study originally appeared on the science blog