Effects of Elevated Carbon Dioxide on vegetation in Tibetan Plateau

At present, effects of climate change on the Tibetan Plateau, characterized mainly by elevated CO₂, slightly increased precipitation and significant increased temperature (0.16 to 0.67°C decade^-1 since the 1950s) (Kuang and Jiao, 2016) on plant growth, have already been concerned by scientists(Fu et al., 2018, Zhao et al., 2019). And as an important part of atmospheric change, elevated CO₂ can improve primary productivity(Zhao et al., 2020, Kuzyakov et al., 2019) and has a critical impact on ecosystem biomass and species diversity on the Tibetan Plateau(Zhao et al., 2020, Zhu et al., 2020).

Free-Air CO₂ Enrichment (FACE) experiments have confirmed that elevated CO₂ can stimulates photosynthetic

carbon gain and primary production over the long term (Leakey et al., 2009). Zhao et al. held the first CO₂ enrichment experiments on the Tibetan Plateau. By using empirical evidence, they assessed the response of plant biomass to elevated CO₂. And they found that elevated CO₂ significantly stimulated plant growth and increased the accumulation of carbon in biomass, but it had no effect on belowground biomass (table 1).

Similar to the study of Zhao et al, based on a 6-yr field experiment in a grassland in Tibetan Plateau, Zhu et al. explored the effects of rising atmospheric CO₂ concentration on aboveground biomass and species diversity (figure 1). And their study revealed that adding CO₂ alone did not change total biomass or species diversity greatly. However when adding CO₂ and N together, biomass and composition of the community altered significantly (figure 2) (Zhu et al., 2020).

Overall, according to the above studies, continuously rising CO₂ has enhanced plant photosynthesis, increased net ecosystem productivity and altered community composition on the Tibetan Plateau. But studies also revealed that, on the plateau, this CO₂ fertilization effect was limited by nitrogen availability (Kou et al., 2020, Zhu et al., 2020) and in the future, plant biomass may have a low growth potential.

Acknowledge:

I am very thankful to Wang Han whose very detailed comments helped to greatly improve the logic and quality of the blog and broadened my view on how to write a discussion and also thanks the suggestions from Han Wang, I. Colin Prentice and Sandy P. Harrison for our ongoing project about Tibetan Plateau leaf area index.

References:

FU, G., SHEN, Z.-X. & ZHANG, X.-Z. 2018. Increased precipitation has stronger effects on plant production of an alpine meadow than does experimental warming in the Northern Tibetan Plateau. Agricultural and Forest Meteorology, 249, 11-21.

KOU, D., YANG, G., LI, F., FENG, X., ZHANG, D., MAO, C., ZHANG, Q., PENG, Y., JI, C., ZHU, Q., FANG, Y., LIU, X., XU, R., LI, S., DENG, J., ZHENG, X., FANG, J. & YANG, Y. 2020. Progressive nitrogen limitation across the Tibetan alpine permafrost region. Nat Commun, 11, 3331.

KUANG, X. & JIAO, J. J. 2016. Review on climate change on the Tibetan Plateau during the last half century. Journal of Geophysical Research: Atmospheres, 121, 3979-4007.

KUZYAKOV, Y., HORWATH, W. R., DORODNIKOV, M. & BLAGODATSKAYA, E. 2019. Review and synthesis of the effects of elevated atmospheric CO2 on soil processes: No changes in pools, but increased fluxes and accelerated cycles. Soil Biology and Biochemistry, 128, 66-78.

LEAKEY, A. D. B., AINSWORTH, E. A., BERNACCHI, C. J., ROGERS, A., LONG, S. P. & ORT, D. R. 2009. Elevated CO2 effects on plant carbon, nitrogen, and water relations: six important lessons from FACE. Journal of Experimental Botany, 60, 2859-2876.

ZHAO, G., LIANG, C., FENG, X., LIU, L., ZHU, J., CHEN, N., CHEN, Y., WANG, L. & ZHANG, Y. 2020. Elevated CO2 decreases soil carbon stability in Tibetan Plateau. Environmental Research Letters, 15.

ZHAO, J., LUO, T., WEI, H., DENG, Z., LI, X., LI, R. & TANG, Y. 2019. Increased precipitation offsets the negative effect of warming on plant biomass and ecosystem respiration in a Tibetan alpine steppe. Agricultural and Forest Meteorology, 279.

ZHU, J., ZHANG, Y., YANG, X., CHEN, N. & JIANG, L. 2020. Synergistic effects of nitrogen and CO2 enrichment on alpine grassland biomass and community structure. New Phytol.